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^v    I 


LIEBIG'S 


COMPLETE  WOEKS  ON 


CHEMISTRY. 


COMPEISING  HIS 


AGRICULTURAL  CHEMISTRY  ;  or,  Organic  Chemistry  in  its  application  to  Agriculture  and 

Physiology.     ANIMAL  CHEMISTRY  ;  or,  Organic  Chemistry  in  its  application  to  Physi- 

ology and  Pathology.     FAMILIAR  LETTERS  ON  CHEMISTRY,  and  its  Relations  to 

Commerce,  Physiology,  and  Agriculture.     THE  ORIGIN  OF  THE  POTATO  DIS- 

EASE ;  and  Researches  into  the  motion  of  the  Juices  in  the  Animal  Body  ; 

and  Evaporation    in   Plants.      CHEMISTRY    AND    PHYSICS    IN 

RELATION  TO  PHYSIOLOGY  AND  PATHOLOGY,  etc.  etc. 


h*   (/  M         a  wtf  c  r 

a- 

BY  JUSTUS  LIEBIG,  M.D.,  PH.D.,  F.RS, 

PROFESSOR  OP  CHEMISTRY  IN  THE  UNIVERSITY  OP  GIESSEN. 


"  It  is  not  too  much  to  say,  that  the  publication  of  Professor  Liebig's  Organic  Chemistry  of  Agriculture  constitutes 
an  era  of  great  importance  in  the  history  of  Agricultural  Science.  Its  acceptance  as  a  standard  is  unavoidable ;  for 
following  closely  in  the  straight  path  of  inductive  Philosophy,  the  conclusions  which  are  drawn  from  its  data  are  incon- 
trovertible. We  can  truly  say,  that  we  have  never  risen  from  the  perusal  of  a  book  with  a  more  thorough  conviction 
of  the  profound  knowledge,  extensive  reading,  and  practical  research  of  its  author,  and  of  the  invincible  power  and 
importance  of  its  reasonings  and  conclusions,  than  we  have  gained  from  the  present  volume." — Silliman's  Journal.^ 

"  Every  page  contains  a  mass  of  information.  I  would  earnestly  advise  all  practical  men,  and  all  interested  in 
cultivation  to  have  recourse  to  the  book  itself.  The  subject  is  vastly  important,  and  we  cannot  estimate  how  much 
may  be  added  to  the  produce  of  our  fields  by  proceeding  on  correct  principles." — London's  Gardener's  Magazine. 

"  The  present  is,  in  short,  the  most  complete  and  the  most  luminous  system  of  Chemistry  in  the  English  language ; 
and  we  know  not  one  in  the  known  world  thai  comes  near  it." — Edinburg  Medical  and  Surgical  Journal. 

"  That  the  public  will  discover  its  merits,  and  that  it  will  find  its  way  into  the  drawing-room  as  well  as  the  library, 
and  be  equally  prized  by  the  advanced  man  of  science  and  the  student,  we  venture  to  say  is  certain;  and  it  must  i»- 
arease  the  respect  entertained  for  Chemistry  wherever  it  is  read." — Chemical  Gazette. 


|J  I) t lab  tip  l)i a: 

T.  B.  PETERSON,  No.  102  CHESTNUT  STEEET. 

PRICE — ONE  DOLLAR  AND  FIFTY  CENTS. 


• 


- 
CHEMISTRY 


IN  ITS  APPLICATION  TO 


AGRICULTUBE  AND  PHYSIOLOGY, 


BY  JUSTUS  LIEBIG,  M.D.,  PH.D.  F.R.S.,  M.R.I.A., 

PI3FESSOR  OF  CHEMISTRY  IN   THE   UNIVERSITY  OF  GIESSEN  J     KNIGHT  OF  THE  HESSIAN  ORDER,  AND  Of 

THE   IMPERIAL   ORDER   OF   SAINT    ANN  ;     MEMBER    OF  THE    ROYAL    ACADEMY    OF    SCIENCES    OP 

STOCKHOLM  ;     CORRESPONDING   MEMBER    OF  THE  ROYAL  ACADEMIES    OF   SCIENCES  OF 

BERLIN  AND  MUNICH  ;   OF  THE  IMPERIAL  ACADEMY  OF  ST.  PETERSBURGH  J   OF 

THE  ROYAL    INSTITUTION    OF    AMSTERDAM,    ETC.    ETC. 


EDITED  FROM  THE  MANUSCRIPT  OF  THE  AUTHOR 

BY  LYON  PLAYFAIR,  PH.D. 


FROM  THE  LAST  LONDON  EDITION,  MUCH  IMPROVED. 


T.  B.  PETERSON,  No.  102  CHESTNUT  STREET. 

ABOVE   THIRD,   GIRARD  STORES. 


TO 

THE  BEITISH  ASSOCIATION 

FOR 

THE    ADVANCEMENT    OF    SCIENCE. 


ONE  of  the  most  remarkable  features  of  modern  times  is  the  combination  of 
large  numbers  of  individuals  representing  the  whole  intelligence  of  nations,  for  the 
express  purpose  of  advancing  science  by  their  united  efforts,  of  learning  its  pro- 
gress, and  of  communicating  new  discoveries.  The  formation  of  such  associations 
is,  in  itself  an  evidence  that  they  were  needed. 

It  is  not  every  one  who  is  called  by  his  situation  in  life  to  assist  in  extending 
the  bounds  of  science ;  but  all  mankind  have  a  claim  to  the  blessings  and  benefits 
which  accrue  from  its  earnest  cultivation.  The  foundation  of  scientific  institutions 
is  an  acknowledgment  of  these  benefits,  and  this  acknowledgment  proceeding  from 
whole  nations  may  be  considered  as  the  triumph  of  mind  over  empiricism. 

Innumerable  are  the  aids  afforded  to  the  means  of  life,  to  manufactures  and  to 
commerce,  by  the  truths  which  assiduous  and  active  inquirers  have  discovered  and 
rendered  capable  of  practical  application.  But  it  is  not  the  mere  practical  utility 
of  these  truths  which  is  of  importance.  Their  influence  upon  mental  culture  is 
most  beneficial ;  and  the  new  views  acquired  by  the  knowledge  of  them  enable  the 
mind  to  recognise,  in  the  phenomena  of  nature,  proofs  of  an  Infinite  Wisdom,  for 
the  unfathomable  profundity  of  which,  language  has  no  expression. 

At  one  of  the  meetings  of  the  chemical  section  of  the  "  British  Association  for 
the  Advancement  of  Science,"  the  honourable  task  of  preparing  a  Report  upon  the 
state  of  Organic  Chemistry  was  imposed  upon  me.  In  the  present  work  I  present 
the  Association  with  a  part  of  this  report. 

I  have  endeavoured  to  develope,  in  a  manner  correspondent  to  the  present  state 
of  science,  the  fundamental  principles  of  Chemistry  in  general,  and  the  laws  of  \ 
Organic  Chemistry  in  particular,  in  their  application  to  Agriculture  and  Physiology  -,  I 
to  the  causes  of  fermentation,  decay,  and  putrefaction ;  to  the  vinous  and  acetous 
fermentations,  and  to  nitrification.     The  conversion  of  woody  fibre  into  wood 
and  mineral  coal,  the  nature  of  poisons,  contagions,  and  miasms,  and  the  causes 
of  their  action  on  the  living  organism,  have  been  elucidated  in  their  chemical 
relations. 

I  shall  be  happy  if  I  succeed  in  attracting  the  attention  of  men  of  science  to 
subjects  which  so  well  merit  to  engage  their  talents  and  energies.  Perfect  Agri- 
culture is  the  true  foundation  of  all  trade  and  industry — it  is  the  foundation  of  the 
riches  of  states.  But  a  rational  system  of  Agriculture  cannot  be  formed  without 
the  application  of  scientific  principles ;  for  such  a  system  must  be  based  on  an 
exact  acquaintance  with  the  means  of  nutrition  of  vegetables,  and  with  the  in- 
fluence of  soils  and  action  of  manure  upon  them.  This  knowledge  we  must  seek 


IV  PREFACE. 

from  chemistry,  which  teaches  the  mode  of  investigating  the  compostion  and  of 
studying  the  characters  of  the  different  substances  from  which  plants  derive  their 
nourishment. 

The  chemical  forces  play  a  part  in  all  the  processes  of  the  living  animal  organ- 
ism ;  and  a  number  of  transformations  and  changes  in  the  living  body  are  exclu- 
sively dependent  on  their  influence.  The  diseases  incident  to  the  period  of  growth 
of  man,  contagion  and  contagious  matters,  have  their  analogues  in  many  chemical 
processes.  The  investigation  of  the  chemical  connection  subsisting  between  those 
actions  proceeding  in  the  living  body,  and  the  transformations  presented  by  chemical 
compounds,  has  also  been  a  subject  of  my  inquiries.  A  perfect  exhaustion  of  this 
subject,  so  highly  important  to  medicine,  cannot  be  expected  without  the  co-opera- 
tion of  physiologists.  Hence  I  have  merely  brought  forward  the  purely  chemical 
part  of  the  inquiry,  and  hope  to  attract  attention  to  the  subject. 

Since  the  time  of  the  immortal  author  of  the  "Agricultural  Chemistry,"  no 
chemist  has  occupied  himself  in  studying  the  applications  of  chemical  principles  to 
the  growth  of  vegetables,  and  to  organic  processes.  I  have  endeavoured  to  follow 
the  path  marked  out  by  Sir  Humphry  Davy,  who  based  his  conclusions  only  on 
that  which  was  capable  of  inquiry  and  proof.  This  is  the  path  of  true  philoso- 
phical inquiry,  which  promises  to  lead  us  to  truth — the  proper  object  of  our 
research. 

In  presenting  this  report  to  the  British  Association  I  feel  myself  bound  to  convey 
my  sincere  thanks  to  Dr.  Lyon  Plairfair,  of  St.  Andrew's,  for  the  active  assistance 
which  has  been  afforded  me  in  its  preparation  by  that  intelligent  young  chemist, 
during  his  residence  in  Giessen.  I  cannot  suppress  the  wish  that  he  may  succeed 
in  being  as  useful,  by  his  profound  and  well  grounded  knowledge  of  chemistry, 
as  his  talents  promise. 

JUSTUS  LIEBIG. 

Gixsen,  September  1,  1852. 


CONTENTS. 


Object  of  the  Work 9 

PART  FIRST. 

ON   THE    CHEMICAL    PROCESSES    IN  THE    NUTRITION   OF   VEGETABLES. 

t0 AFTER  PAGE 

I. — On  the  Constituent  Elements  of  Plants 10 

II. — On  the  Assimilation  of  Carbon 12 

III. — On  the  Origin  and  Action  of  Humus 23 

IV. — On  the  Assimilation  of  Hydrogen 27 

V. — On  the  Origin  and  Assimilation  of  Nitrogen    ....  30 

VI. — On  the  Inorganic  Constituents  of  Plants      ....  36 

VII.— The  Art  of  Culture 43 

VIII. — On  the  Alternation  (Rotation)  of  Crops      ....  54 

IX.— On  Manure 59 

Supplementary  Chapter. — On  the  Chemical  Constituents  of  Soils    .  70 

Appendix  to  Part  1 84 


PART  SECOND. 

ON  THE    CHEMICAL   PROCESSES    OP    FERMENTATION,   DECAY,    AND    PUTREFACTION. 

CHAPTER  PAQK 

I. — Chemical  Transformations 87 

II. — On  the  Causes  which  effect  Fermentation,  Decay,  and  Putre- 
faction   88 

[II. — Fermentation  and  Putrefaction 90 

IV. — On  the  Transformation  of  Bodies  which  do  not  contain  Nitro- 
gen as  a  constituent,  and  of  those  in  which  it  is  present  92 

V. — Fermentation  of  Sugar 95 

VI. — Eremacausis,  or  Decay         .......  98 

VII. — Eremacausis  of  Bodies  destitute  of  Nitrogen:  Formation  of 

Acetic  Acid     .        .        .        .        .        .        .        .        .  100 

VIII. — Eremacausis  of  Substances  containing  Nitrogen:  Nitrification  102 

IX. — On  Vinous  Fermentation :  Wine  and  Beer  .        .        .        .  103 

X. — On  the  Decay  of  Woody  Fibre 110 

XL— On  Vegetable  Mould 112 

XII. — On  the  Mouldering  of  Bodies :  Paper,  Brown  Coal,  and  Mi- 
neral Coal 112 

XIII. — On  Poisons,  Contagions,  and  Miasms 115 

Appendix  to  Part  II 129 

Index  131 


EDITOR'S  PREFACE. 


THE  former  edition  of  this  work  was  prepared  in  the  form  of  a  report  on  the 
present  state  of  Organic  Chemistry.  The  state  of  a  science  such  as  this  could  not 
be  exhibited  by  a  systematic  treatise  on  organic  compounds,  but  by  showing  that 
the  science  was  so  far  advanced  as  to  be  useful  in  its  practical  applications. 

The  work  was  written  by  a  Chemist,  and  addressed  to  Chemists.  The  author 
did  not  flatter  himself  that  his  opinions  would  be  so  eagerly  embraced  by  agricul- 
turists, as  circumstances  have  shown  to  be  the  case.  Hence  his  language  and  style 
were  less  adapted  for  them  than  for  those  who  are  conversant  with  the  abstract 
details  of  chemical  science.  But  the  eager  reception  of  the  work  by  agriculturists 
has  shown  that  they  possess  an  ardent  desire  to  profit  by  the  aids  offered  to  them 
V>y  Chemistry.  It,  therefore,  became  necessary  to  adapt  the  work  for  those  who 
have  not  had  an  opportunity  of  making  that  science  a  peculiar  object  of  study. 

The  Editor  has  endeavoured  to  effect  this  change.  In  doing  so,  it  was  necessary 
to  retain  the  original  character  of  the  work ;  hence  those  alterations  omy  have 
been  made  which  are  calculated  to  render  the  work  more  generally  useful.  It 
must  be  remembered  that  the  object  of  the  author  was  not  to  write  a  "  System  of 
Agricultural  Chemistry,"  but  to  furnisn  a  "  Treatise  on  the  Chemistry  of  Agricul- 
ture." It  is  to  be  hoped  that  those  who  are  acquainted  with  the  general  doctrines 
of  Chemistry  will  find  no  difficulty  in  comprehending  any  of  the  principles  here 
developed. 

The  author  has  enriched  the  present  edition  with  many  valuable  additions; 
allusion  may  be  particularly  made  to  the  practical  illustration  of  his  principles 
furnished  in  the  Supplementary  Chapter  on  Soils.  The  analyses  of  soils  contained 
in  that  chapter  will  serve  to  point  out  the  culpable  negligence  exhibited  in  the 
examination  of  English  soils.  Even  in  the  analyses  of  professional  chemists, 
published  in  detail,  and  with  every  affectation  of  accuracy,  the  estimation  of  the 
most  important  ingredients  is  neglected.  How  rarely  do  we  find  phosphoric  acid 
among  the  products  of  their  analyses?  potash  and  soda  would  appear  to  be 
absent  from  all  soils  in  the  British  territories !  Yet  these  are  invariable  constituents 
of  fertile  soils,  and  are  conditions  indispensable  to  their  fertility. 

Primrose,  November  22,  1852. 


ORGANIC   CHEMISTRY 


ITS   APPLICATIOK    TO 


VEGETABLE  PHYSIOLOGY  AND  AGRICULTURE. 


THE  object  of  Chemistry  is  to  examine 
'nto  the  composition  of  the  numerous  modifi- 
cations of  matter  which  occur  in  the  organic 
and  inorganic  kingdoms  of  nature,  and  to 
investigate  the  laws  by  which  the  combina- 
tion and  decomposition  of  their  parts  is 
effected. 

Although  material  substances  assume  a 
vast  variety  of  forms,  yet  chemists  have  not 
been  able  to  detect  more  than  fifty-five 
bodies  which  are  simple,  or  contain  only 
one  kind  of  matter,  and  from  these  all  other 
substances  are  produced.  They  are  con- 
sidered simple  only  because  it  has  not  been 
proved  that  they  consist  of  two  or  more 
parts.  The  greater  number  of  the  elements 
occur  in  the  inorganic  kingdom.  Four  only 
are  found  in  organic  matter. 

But  it  is  evident  that  this  limit  to  their 
number  must  render  it  more  difficult  to  as- 
certain the  precise  circumstances  under 
which  their  union  is  effected,  and  the  laws 
which  regulate  their  combinations.  Hence 
chemists  have  only  lately  turned  their  at- 
tention to  the  study  of  the  nature  of  bodies 
generated  by  organized  beings.  A  few 
years  have,  ^however,  sufficed  to  throw 
much  light  upon  this  interesting  depart- 
ment of  science,  and  numerous  facts  have 
been  discovered  which  cannot  fail  to  be 
of  importance  in  their  practical  applica- 
tions. 

The  peculiar  object  of  organic  chemistry 
is  to  discover  the  chemical  conditions  essen- 
tial to  the  life  and  perfect  development  of 
animals  and  vegetables,  and  generally  to  in- 
vestigate all  those  processes  of  organic 
nature  which  are  due  to  the  operation  of 
chemical  laws.  Now,  the  continued  exist- 
ence of  all  living  beings  is  dependent  on  the 
reception  by  them  of  certain  substances, 
which  are  applied  to  the  nutrition  of  their 
frame.  An  inquiry,  therefore,  into  the  con- 
ditions on  which  the  life  and  growth  of 
living  beings  depend,  involves  the  study  of 
those  substances  which  serve  them  as  nutri- 
ment, as  well  as  the  investigation  of  the 
sources  whence  these  substances  are  derived, 
2 


and  the  changes  which  they  undergo  in  the 
prpcess  of  assimilation. 

LA  beautiful  connection  subsists  between 
the  organic  and  inorganic  kingdoms  of  na- 
ture. Inorganic  matter  affords  food  to 
plants,  and  they,  on  the  other  hand,  yield 
the  means  of  subsistence  to  animals.  The 
conditions  necessary  for  animal  and  veget- 
able nutrition  are  essentially  different.  An 
animal  requires  for  its  development,  and  fo? 
the  sustenance  of  its  vital  functions,  a  cer- 
tain class  of  substances  which  can  only  be 
generated  by  organic  beings  possessed  of 
life.  Although  many  animals  are  entirely 
carnivorous,  yet  their  primary  nutriment 
must  be  derived  from  plants ;  for  the  animals 
upon  which  they  subsist  receive  their  nour- 
ishment from  vegetable  matter.  But  plants 
find  new  nutritive  material  only  in  inorganic 
substances.  Hence  one  great  end  of  veget- 
able life  is  to  generate  matter  adapted  for 
the  nutrition  of  animals  out  of  inorganic 
substances,  which  are  not  fitted  for  this  pur- 
pose. Now  the  purport  of  this  work  is,  to 
elucidate  the  chemical  processes  engaged  in 
the  nutrition  of  vegetables.! 

The  first  part  of  it  will  be  devoted  to  the 
examination  of  the  matters  which  supply 
the  nutriment  of  plants,  and  of  the  changes 
which  these  matters  undergo  in  the  living 
organism.  The  chemical  compounds  which 
afford  to  plants  their  principal  constituents, 
viz.,  carbon  and  nitrogen,  will  here  come 
under  consideration,  as  well  as  the  relations 
in  which  the  vital  functions  of  vegetables 
stand  to  those  of  the  animal  economy  and  to 
other  phenomena  of  nature. 

The  second  part  of  the  work  will  treat  of 
the  chemical  processes  which  effect  the 
complete  destruction  of  plants  and  animals 
after  death,  such  as  the  peculiar  modes  of 
decomposition,  usually  described  asfermen* 
tation,  putrefaction,  and  decay;  and  in  this 
part  the  changes  which  organic  substances 
undergo  in  their  conversion  into  inorganic 
compounds,  as  well  as  the  causes  which 
determine  these  changes,  will  become  matter 
of  inquiry. 

B 


PAET  I. 


OF  THE  CHEMICAL  PROCESSES  IN  THE  NUTRITION  OF  VEGETABLFS- 


CHAPTER  I. 

01'  THE  CONSTITUENT  ELEMENTS  OF  PLANTS. 

THE  ultimate  constituents  of  plants  are 
those  which  form  organic  matter  in  general, 
namely,  Carbon,  Hydrogen,  Nitrogen,  and 
Oxygen.  These  elements  are  always  pre- 
sent in  plants,  and  produce  by  their  union 
the  various  proximate  principles  of  which 
they  consist.  It  is,  therefore,  necessary  to 
be  acquainted  with  their  individual  charac- 
ters, for  it  is  only  by  a  correct  appreciation 
of  these  that  we  are  enabled  to  explain  the 
functions  which  they  perform  in  the  veget- 
able organization. 

Carbon  is  an  elementary  substance,  en- 
dowed with  a  considerable  range  of  affinity. 
With  oxygen  it  unites  in  two  proportions, 
forming  the  gaseous  compounds  known 
under  the  names  of  carbonic  acid  and  car- 
bonic oxide.  The  former  of  these  is  emit- 
ted in  immense  quantities  from  many  vol- 
canoes and  mineral  springs,  and  is  a  product 
of  the  combustion  and  decay  of  organic 
matter.  It  is  subject  to  be  decomposed  by 
various  agencies,  and  its  elements  then  ar- 
range themselves  into  new  combinations. 
Carbon  is  familiarly  known  as  charcoal,  but 
in  this  state  it  is  mixed  with  several  earthy 
bodies ;  in  a  state  of  absolute  purity  it  con- 
stitutes the  diamond. 

Hydrogen  is  a  very  important  constituent 
of  vegetable  matter.  It  possesses  a  special 
affinity  for  oxygen,  with  which  it  unites  and 
forms  water.  The  whole  of  the  phenomena 
of  decay  depend  upon  the  exercise  of  this 
affinity,  and  many  of  the  processes  engaged 
in  the  nutrition  of  plants  originate  in  the 
attempt  to  gratify  it.  Hydrogen,  when  in 
the  state  of  a  gas,  is  very  combustible,  and 
the  lightest  body  known;  but  it  is  never 
found  in  nature  in  an  isolated  condition. 
Water  is  the  most  common  combination  in 
which  it  is  presented;  and  it  may  be  re- 
moved by  various  processes  from  the  oxygen, 
with  which  it  is  united  in  this  body. 

Nitrogen  is  quite  opposed  in  its  chemical 
characters  to  the  two  bodies  now  described. 
Its  principal  characteristic  is  an  indifference 
to  all  other  substances,  and  an  apparent  re- 
luctance to  enter  into  combination  with 
them.  When  forced  by  peculiar  circum- 
stances to  do  so,  it  seems  to  remain  in  the 
combination  by  a  vis  inertia:;  and  very 
slight  forces  effect  the  disunion  of  these 
feeble  compounds. 

Yet  nitrogen  is  an  invariable  constituent 


of  plants,  and  during  their  life  is  subject  to 
the  control  of  the  vital  powers.  But  when 
the  mysterious  principle  of  life  has  ceased 
to  exercise  its  influence,  this  element  re- 
sumes its  chemical  character,  and  materially 
assists  in  promoting  the  decay  of  vegetable 
matter,  by  escaping  from  the  compounds  of 
which  it  formed  a  constituent. 

Oxygen,  the  only  remaining  constituent 
of  organic  matter,  is  a  gaseous  element, 
which  plays  a  most  important  part  in  the 
economy  of  nature.  It  is  the  agent  em- 
ployed in  effecting  the  union  and  disunion 
of  a  vast  number  of  compounds.  It  is  supe- 
rior to  all  other  elements  in  the  extensive 
range  of  its  affinities.  The  phenomena  of 
combustion  and  decay  are  examples  of  the 
exercise  of  its  power. 

Oxygen  is  the  most  generally  diffused 
element  on  the  surface  of  the  earth ;  for, 
besides  constituting  the  principal  part  of  the 
atmosphere  which  surrounds  it,  it  is  a  com- 
ponent of  almost  all  the  earths  and  minerals 
found  on  its  surface.  In  an  isolated  state  it 
is  a  gaseous  body,  possessed  of  neither  taste 
nor  smelL  It  is  slightly  soluble  in  water, 
and  hence  is  usually  found  dissolved  in  rain 
and  snow,  as  well  as  in  the  water  of  running 
streams. 

Such  are  the  principal  characters  of  the 
elements  which  constitute  organic  matter ; 
but  it  remains  for  us  to  consider  in  what 
form  they  are  united  in  plants. 

The  substances  which  constitute  the  prin- 
cipal mass  of  every  vegetable  are  com- 
pounds of  carbon  with  oxygen  and  hydro- 
gen, in  the  proper  relative  proportions  for 
forming  water.  Woody  fibre,  starch,  sugar, 
and  gum,  for  example,  are  such  compounds 
of  carbon  with  the  elements  of  water.  In 
another  class  of  substances  containing  car- 
bon as  an  element,  oxygen  and  hydrogen  are 
again  present;  but  the  proportion  of  oxygen 
is  greater  than  would  be  required  for  produc- 
ing water  by  union  with  the  hydrogen.  The 
numerous  organic  acids  met  with  in  plants 
belong,  with  few  exceptions,  to  this  class 

A  third  class  of  vegetable  compounds 
contains  carbon  and  hydrogen,  but  no  oxy- 
gen, or  less  of  that  element  than  would  be 
required  to  convert  all  the  hydrogen  into 
water.  These  may  be  regarded  as  com- 
pounds of  carbon  with  the  elements  of 
water,  and  an  excess  of  hydrogen.  Such 
are  the  volatile  and  fixed  oils,  wax,  and  the 
resins.  Many  of  them  have  acid  characters. 

The  juices  of  all  vegetables  contain  or- 
ganic acids,  generally  combined  with  the 

10 


THE    ATMOSPHERE.— SOILS. 


II 


inorganic  bases,  or  metallic  oxides;  for  these 
metalic  oxides  exist  in  every  plant,  and  may 
be  detected  in  its  ashes  after  incineration. 

Nitrogen  is  an  element  of  vegetable  albu- 
men and  gluten;  it  is  a  constituent  of  the 
acid,  and  of  what  are  termed  the  "  indiffer- 
ent substances1'  of  plants,  as  well  as  of 
those  peculiar  vegetable  compounds  which 
possess  all  the  properties  of  metallic  oxides, 
and  are  known  as  "  organic  bases." 

Estimated  by  ;ts  proportional  weight,  ni- 
trogen forms  only  a  very  small  part  of  plants ; 
but  it  is  never  entirely  absent  from  any  part 
of  them.  Even  when  it  does  not  absolutely 
enter  into  the  composition  of  a  particular 
part  or  organ,  it  is  always  to  be  found  in  the 
fluids  which  pervade  it. 

It  follows  from  the  facts  thus  far  detailed, 
that  the  development  of  a  plant  requires 
the  presence,  first,  of  substances  containing 
carbon  and  nitrogen,  and  capable  of  yield- 
ing these  elements  to  the  growing  organism ; 
secondly,  of  water  and  its  elements;  and 
lastly,  of  a  soil  to  furnish  the  inorganic 
matters  which  are  likewise  essential  to  ve- 
getable life. 

OP  THE  COMPOSITION  OF  THE  ATMOSPHERE. 

In  the  normal  state  of  growth  plants  can 
only  derive  their  nourishment  from  the 
atmosphere  and  the  soil.  Hence  it  is  of 
importance  to  be  acquainted  with  the  com- 
position of  these,  in  order  that  we  may  be 
enabled  to  judge  from  which  of  their  con- 
stituents the  nourishment  is  afforded. 

The  composition  of  the  atmosphere  has 
been  examined  by  many  chemists  with  great 
care,  and  the  result  of  their  researches  have 
shown,  that  its  principal  constituents  are 
always  present  in  the  same  proportion. 
These  are  the  two  gases,  oxygen  and  nitro- 
gen, the  general  properties  of  which  have 
been  already  described.  One  hundred  parts, 
by  weight,  of  atmospheric  air  contain  23'1 
parts  of  oxygen,  and  76'9 parts  of  nitrogen; 
or  100  volumes  of  air  contain  nearly  21 
volumes  of  oxygen  gas.  From  the  exten- 
sive range  of  affinity  which  this  gas  pos- 
sesses, it  is  obvious,  that  were  it  alone  to 
constitute  our  atmosphere,  and  left  un- 
checked to  exert  its  powerful  effects,  all  na- 
ture would  be  one  scene  of  universal  destruc- 
tion. It  is  on  this  account  that  nitrogen  is 
present  in  the  air  in  so  large  proportion.  It  is 
peculiarly  adapted  for  this  purpose,  as  it  does 
not  possess  any  disposition  to  unite  with  oxy- 
gen, and  exerts  no  action  upon  the  processes 
proceeding  on  the  earth.  These  two  gases 
are  intimately  mixed,  by  virtue  of  a  pro- 
perty which  all  gasses  possess  in  common, 
of  diffusing  themselves  equally  through 
every  part  of  another  gas,  with  which  they 
are  placed  in  contact. 

Although  oxygen  and  nitrogen  form  the 
principal  constituents  of  the  atmosphere, 
yet  they  are  not  the  only  substances  found 
in  it.  Watery  vapour  and  carbonic  acid  gas 
materially  modify  its  properties.  The  for- 


mer of  these  falls  upon  the  earth  as  rain, 
and  brings  with  it  any  soluble  matter  which 
it  meets  in  its  passage  through  the  air. 

Carbonic  acid  gas  is  discharged  in  im- 
mense quantities  from  the  active  volcanoes 
of  America,  and  from  many  of  the  mineral 
springs  which  abound  in  various  parts  of 
Europe;  it  is  also  generated  during  the 
combustion  and  decay  of  organic  matter. 
It  is  not,  therefore,  surprising  that -it  should 
have  been  detected  in  every  part  of  the 
atmosphere  in  which  its  presence  has  been 
looked  for.  Saussure  found  it  even  in  the 
air  on  the  summit  of  Mont  Blanc,  which  is 
covered  with  perpetual  snow,  and  where  it 
could  not  be  produced  by  the  immediate 
agency  of  vegetable  matter.  Carbonic  acid 
gas  performs  a  most  important  part  in  the 
process  of  vegetable  nutrition,  the  considera- 
tion of  which  belongs  to  another  part  of  the 
work. 

Carbonic  acid,  water,  and  ammonia  (a 
compound  of  hydrogen  and  nitrogen)  are 
the  final  products  of  the  decay  of  animal  and 
vegetable  matter.  In  an  isolated  condition, 
they  usually  exist  in  the  gaseous  form. 
Hence,  on  their  formation,  they  must  escape 
into  the  atmosphere.  But  ammonia  has  not 
hitherto  been  enumerated  among  the  con- 
stituents of  the  air,  although,  according  to 
our  view,  it  can  never  be  absent.  The  rea- 
son of  this  is,  that  it  exists  in  extremely  mi- 
nute quantity  in  the  amount  of  air  usually 
subjected  to  experiment  in  chemical  analy- 
sis ;  it  has  consequently  escaped  detection. 
But  rain  which  falls  through  a  large  extent 
of  air,  carries  down  in  solution  all  that  re- 
mains in  suspension  in  it.  Now  ammonia 
always  exists  in  rainwater,  and  from  this 
fact  we  must  conclude  that  it  is  invariably 
present  in  the  atmosphere.  Nor  can  we  be 
surprised  at  its  presence  when  we  consider 
that  many  volcanoes  now  in  activity  emit 
large  quantities  of  it.  This  subject  will, 
however,  be  discussed  more  fully  in  anothei 
part  of  the  work. 

Such  are  the  principal  constituents  of  the 
atmosphere  from  which  plants  derive  their 
nourishment;  for  although  other  matters  are 
supposed  to  exist  in  it  in  minute  quantity, 
yet  they  do  not  exercise  any  influence  on 
vegetation,  nor  has  even  their  presence  been 
satisfactorily  demonstrated. 

OP  SOILS. 

A  soil  may  be  considered  a  magazine  01 
inorganic  matters,  which  are  prepared  by 
the  plant  to  suit  the  purposes  destined  for 
them  in  its  nutrition.  The  composition  and 
uses  of  such  substances  cannot,  however, 
be  studied  with  advantage,  until  we  have 
considered  the  manner  in  which  the  organic 
matter  is  obtained  by  plants. 

Some  virgin  soils,  such  as  those  of  Ame- 
rica, contain  vegetable  matter  in  large  pro- 
portion ;  and  as  these  have  been  found  emi- 
nently adapted  for  the  cultivation  of  most 
plants,  the  organic  matter  contained  in  them 


12 


AGRICULTURAL    CHEMISTRY. 


has  naturally  been  recognised  as  the  cause 
of  their  fertility.  To  this  matter,  the  terra 
"  vegetable  mould"  or  humus  has  been  ap- 
plied. Indeed,  this  peculiar  substance  ap- 
pears to  play  such  an  important  part  in  the 
phenomena  of  vegetation,  that  vegetable 
physiologists  have  been  induced  to  ascribe 
the  fertility  of  every  soil  to  its  presence.  It 
is  believed  by  many  to  be  the  principal  nu- 
triment of  plants,  and  is  supposed  to  be  ex- 
tracted by  them  from  the  soil  in  which  they 
grow.  It  is  itself  the  product  of  the  decay 
of  vegetable  matter,  and  must,  therefore,  con- 
tain many  of  the  constituents  which  are 
found  in  plants  during  life.  Its  action  will, 
therefore,  be  examined  in  considering  whence 
these  constituents  are  derived. 


CHAPTER  II. 

OF    THE    ASSIMILATION    OF    CARBON. 
COMPOSITION  OF  HUMUS. 

THE  humus,  to  which  allusion  has  been 
made,  is  described  by  chemists  as  a  brown 
substance  easily  soluble  in  alkalies,  but  only 
slightly  so  in  water,  and  produced  during 
the  decomposition  of  vegetable  matters  by 
the  action  of  acids  or  alkalies,  k  has,  how- 
ever, received  various  names  according  to 
the  different  external  characters  and  chemi- 
cal properties  which  it  presents.  Thus, 
ulmin,  humic  acid,  coal  of  humus,  and  humin, 
are  names  applied  to  modifications  of  humus. 
They  are  obtained  by  treating  peat,  woody 
fibre,  soot,  or  brown  coal  with  alkalies ;  by 
decomposing  sugar,  starch,  or  sugar  of  milk: 
by  means  of  acids;  or  by  exposing  alkaline 
solutions  of  tannic  and  gallic  acids  to  the 
action  of  the  air. 

The  modifications  of  humus  which  are 
soluble  in  alkalies,  are  called  humic  acid; 
while  those  which  are  insoluble  have  re- 
ceived the  designations  of  humin  and  coal  of 
humas. 

The  names  given  to  these  substances 
might  cause  it  to  be  supposed  that  their 
composition  is  identical.  But  a  more  erro- 
neous notion  could  not  be  entertainad ;  since 
even  sugar,  acetic  acid,  and  resin  do  not 
differ  more  widely  in  the  proportions  of  their 
constituent  elements,  than  do  the  various 
modifications  of  humus. 

Humic  acid  formed  by  the  action  of  hy- 
drate of  potash  upon  sawdust  contains,  ac- 
cording to  the  accurate  analysis  of  Peligot, 
72  per  cent,  of  carbon,  while  the  humic  acid 
obtained  from  turf  and  brown  coal  contains, 
according  to  Sprengel,  only  58  per  cent.; 
that  prod  ced  by  the  action  of  dilute  sul- 
phuric acid  upon  sugar,  57  per  cent,  accord- 
ing to  Malaguti;  and  that,  lastly,  which  is 
obtained  from  sugar  or  from  starch,  by  means 
of  muriatic  acid,  according  to  the  analysis 
of  Stein,  64  per  cent.  All  these  analyses 
have  been  repeated  with  care  and  accuracy, 


and  the  proportion  of  carbon  in  \he  respective 
cases  has  been  found  to  agree  with  the  esti- 
mates of  the  differen  chemists  above  men- 
tioned ;  so  that  there  is  no  reason  to  ascribe 
the  difference  in  this  respect  between  the 
varieties  of  humus  to  the  mere  difference  in 
the  methods  of  analysis  or  degrees  of  ex- 
pertness  of  the  operators.  Malaguti  states, 
moreover,  that  humic  acid  contains  an  equal 
number  of  equivalents  of  oxygen  and  hy- 
drogen, that  is  to  say,  that  these  elements 
exist*  in  it  in  the  proportions  for  forming 
water;  while,  according  to  Sprengel,  the 
oxygen  is  in  excess,  and  Peligot  even  esti- 
mates the  quantity  of  oxygen  at  14  equiva- 
lents, and  the  hydrogen  at  only  6  equiva- 
lents, making  the  deficiency  of  hydrogen  as 
great  as  8  equivalents.  And  although  Mul- 
der* has  very  recently  explained  many  of 
these  conflicting  results,  by  showing  that 
there  are  several  kinds  of  humus  and  humic 
acids  essentially  distinct  in  their  characters, 
and  fixed  in  their  composition,  yet  he  has 
afforded  no  proof  that  the  definite  compounds 
obtained  by  him  really  exist,  as  such,  in  the 
soil.  On  the  contrary,  they  appear  to  have 
been  formed  by  the  action  of  the  potash  and 
ammonia,  which  he  employed  in  their  pre- 
paration. 

It  is  quite  evident,  therefore,  that  chemists 
have  been  in  the  habit  of  designating  all 
products  of  the  decomposition  of  organic 
bodies  which  had  a  brown  or  brownish 
black  colour,  by  the  names  of  humic  acid  or 
humin,  according  as  they  were  soluble  or 
insoluble  in  alkalies ;  although  in  their 
composition  and  mode  of  origin,  the  sub- 
stances thus  confounded  might  be  in  no 
way  allied. 

Not  the  slightest  ground  exists  for  the  be- 
lief that  one  or  other  of  these  artificial  pro- 
ducts of  the  decomposition  of  vegetable 
matters  exists  in  nature  in  the  form  and  en- 
dowed with  the  properties  of  the  vegetable 
constituents  of  mould ;  there  is  not  the 
shadow  of  a  proof  that  one  of  them  exerts 
any  influence  on  the  growth  of  plants  eithei 
in  the  way  of  nourishment  or  otherwise. 

Vegetable  physiologists  have,  without  any 
apparent  reason,  imputed  the  known  pro- 
perties of  the  humus  and  humic  acids  of 
chemists  to  that  constituent  of  mould  which 
has  received  the  same  name,  and  in  this 
way  have  been  led  to  their  theoretical  no- 
tions respecting  the  functions  of  the  latter 
substance  in  vegetation. 

The  opinion  that  the  substance  called 
humus  is  extracted  from  the  soil  by  the  roots 
of  plants,  and  that  the  carbon  entering  into 
its  composition  serves  in  some  form  or 
other  to  nourish  their  tissues,  is  considered 
by  many  as  so  firmly  established  that  any 
new  argument  in  its  favour  has  been  deemed 
unnecessary ;  the  obvious  difference  in  the 
growth  of  plants  according  to  the  known 
abundance  or  scarcity  of  humus  in  the  soil. 


*  Bulletin  des  Scienc.  Phys.  et  Natur.  de  Neerl. 
1840,  p.  1—102. 


ABSORPTION  OF  HUMIS. 


13 


seemed  to   afford  incontestable  proof  of  its 
correctness.* 

Yet,  this  position,  when  submitted  to  a 
strict  examination,  is  found  to  be  untenable, 
and  it  becomes  evident  from  most  conclusive 
proofs  that  humus  in  the  form  in  which  it 
exists  in  the  soil,  does  not  yield  the  smallest 
nourishment  to  plants. 

The  adherence  to  the  above  incorrect 
opinion  has  hitherto  rendered  it  impossible 
or  the  true  theory  of  the  nutritive  process 
/n  vegetables  to  become  known,  and  has  thus 
deprived  us  of  our  best  guide  to  a  rational 
practice  in  agriculture.  Any  great  improve- 
ment in  that  most  important  of  all  arts  is  in- 
conceivable without  a  deeper  and  more  per- 
fect acquaintance  with  the  substances  which 
nourish  plants,  and  with  the  sources  whence 
they  are  derived ;  and  no  other  cause  can 
be  discovered  to  account  for  the  fluctuating 
and  uncertain  state  of  our  knowledge  on 
this  subject  up  to  the  present  time,  than 
that  modern  physiology  has  not  kept  pace 
with  the  rapid  progress  of  chemistry. 

In  the  following  inquiry  we  shall  suppose 
the  humus  of  vegetable  physiologists  to  be 
really  endowed  with  the  properties  recog- 
nised by  chemists  in  the  brownish  black  de- 
posits which  they  obtain  by  precipitating  an 
alkaline  decoction  of  mould  or  peat  by 
means  of  acids,  and  which  they  name  humic 
acid. 

Humic  acid,  when  first  precipitated,  is  a 
flocculent  substance,  is  soluble  in  2500 
times  its  weight  of  water,  and  combines 
with  alkalies,  lime  and  magnesia,  forming 
compounds  of  the  same  degree  of  solubility. 
(Sprengel.) 

Vegetable  physiologists  agree  in  the  sup- 
position that  by  the  aid  of  water  humus  is 
rendered  capable  of  being  absorbed  by  the 
roots  of  plants.  But  according  to  the  ob- 
servation of  chemists,  humic  acid  is  soluble 
only  when  newly  precipitated,  and  becomes 
completely  insoluble  when  dried  in  the  air, 
or  when  exposed  in  the  moist  state  to  the 
freezing  temperature.  (Sprengel.) 

Both  the  cold  of  winter  and  the  heat  of 
summer,  therefore,  are  destructive  of  the  solu- 
bility of  hurnic  acid,  and  at  the  same  time  of 
its  capability  of  being  assimilated  by  plants. 
So  that,  if  it  is  absorbed  by  plants,  it  must 
be  in  some  altered  form. 

The  correctness  of  these  observations  is 
easily  demonstrated  by  treating  a  portion  of 
good  mould  with  cold  water.  The  fluid  re- 
mains colourless,  and  is  found  to  have  dis- 
solved less  than  100,000  part  of  its  weight 
of  organic  matters,  and  to  contain  merely 
the  salts  which  are  present  in  rainwater. 

Decayed  oak  wood,  likewise,  of  which 
humic  acid  is  the  principal  constituent,  was 
found  by  Berzelius  to  yield  to  cold  water 

*  This  remark  applies  more  to  German  than 
to  English  botanists  and  physiologists.  In  Eng- 
land, the  idea  that  humus,  as  such,  affords  nour- 
ishment to  plants  is  by  no  means  general  ;  but  on 
the  Continent,  the  views  of  Berzelius  on  this  sub- 
ject have  been  almost  universally  adopted.— ED. 


only  slight  traces  of  soluble  materials  ;  and 
I  have  myself  verified  this  observation  on 
the  decayed  wood  of  beech  and  fir. 

These  facts,  whicn  show  that  humic,  in 
its  unaltered  condition,  cannot  serve  for  the 
nourishment  of  plants,  have  not  escaped  the 
notice  of  physiologists ;  and  hence  they  have 
assumed  that  the  lime  or  the  different  alka- 
lies found  in  the  ashes  of  vegetables  render 
soluble  the  humic  acid  and  fit  it  for  the  pro- 
cess of  assimulation. 

Alkalies  and  alkaline  earths  do  exist  in 
the  different  kinds  of  soil  in  sufficient  quan- 
tity to  form  such  soluble  compounds  with 
the  humic  acid. 

Now,  let  us  suppose  that  humic  acid  is 
absorbed  by  plants  in  the  form  of  that  salt 
which  contains  the  largest  proportion  of 
humic  acid,  namely,  in  the  form  of  humate 
of  lime,  and  then  from  the  known  quantity 
of  the  alkaline  bases  contained  in  the  ashes 
of  plants,  let  us  calculate  the  amount  ol 
humic  acid  which  might  be  assimulaied  in 
this  manner.  Let  us  admit,  likewise,  that 
potash,  soda,  and  the  oxides  of  iron  and 
manganese  have  the  same  capacity  of  satu- 
ration as  lime  with  respect  to  humic  acid, 
and  then  we  may  take  as  the  basis  of  our 
calculation  the  analysis  of  M.  Berthier,  who 
I  found  that  1000  Ibs.  of  dry  fir  wood  yielded 
;  4  Ibs.  of  ashes,  and  that  in  every  100  Ibs.  of 
these  ashes,  after  the  chloride  of  potassium 
and  sulphate  of  potash  were  extracted,  53 
j  Ibs.  consisted  of  the  basic  metallic  oxides, 
'  potash,  soda,  lime,  magnesia,  iron,  and 
manganese. 

One  Hessian  acre*  of  woodland  yields 
annually,  according  to  Dr.  Heyer,  on  an 
average,  2920  Ibs.  of  dry  fir  wood,  which 
|  contain  6.17  Ibs.  of  metallic  oxides. 

Now,  according  to  the  estimates  of  Mala- 
guti  and  Sprengel,  1  Ib.  of  lime  combines 
chemically  with  12  Ibs.  of  humic  acid  ;  6.17 
Ibs.  of  the  metallic  oxides  would  accordingly 
introduce  into  the  trees  67  Ibs.  of  humic 
acid,  which,  admitting  humic  acid  to  con- 
tain 58  per  cent,  of  carbon,  would  corres- 
pond to  100  Ibs.  of  dry  wood.  But  we  have 
|  seen  that  2920  Ibs.  of  fir  wood  are  really- 
produced. 

Again,  if  the  quantity  of  humic  acid 
which  might  be  introduced  into  wheat  in 
the  form  of  humates  is  calculated  from  the 
known  proportion  of  metallic  oxides  exist- 
ing in  wheat  straw,  (the  sulphates  and 
chlorides  also  contained  in  the  ashes  of  the 
straw  not  being  included,  it  will  be  found 
that  the  wheat  growing  on  1  Hessian  acre 
would  receive  in  that  way  63  Ibs.  of  humic 
acid,  corresponding  to  93.6  Ibs.  of  woody 
fibre.  But  the  extent  of  land  just  mentioned 
produces,  independently  of  the  roots  and 
grain,  1961  Ibs.  of  straw,  the  composition 
of  which  is  the  same  as  that  of  woody  fibre. 

It  has  been  taken  for  granted  in  these  cal- 


*  One  Hessian  acre  is  equal  to  40,000  square 
feet,  Hessian,  or  26,910  square  feet,  English  mea- 

B1U*. 


J4 


AGRICULTURAL    CHEMISTRY. 


culations  that  the  basic  metallic  oxides 
which  have  served  to  introduce  humic  acid 
into  the  plants  do  not  return  to  the  soil, 
since  it  is  certain  that  they  remain  fixed  in 
the  parts  newly  formed  during  the  process 
of  growth. 

Let  us  now  calculate  the  quantity  of 
humic  acid  which  plants  can  receive  under 
the  most  favourable  circumstances,  viz. 
the  agency  of  rainwater. 

The  quantity  of  rain  which  falls  at  Er- 
furt, one  of  the  most  fertile  districts  of  Ger- 
many, during  the  months  of  April,  May, 
June,  and  July,  is  stated  by  Schubler  to  be 
19.3  Ibs.  over  every  square  foot  of  surface ; 
1  Hessian  acre,  or  26,910  square  feet,  con- 
sequently receive  771,000  Ibs.  of  rainwater. 

If,  now,  we  suppose  that  the  whole  quan- 
tity of  this  rain  is  taken  up  by  the  roots  of  a 
summer  plant,  which  ripens  four  months 
after  it  is  planted,  so  that  not  a  pound  of 
this  water  evaporates  except  from  the  leaves 
of  the  plant ;  and  if  we  farther  assume  that 
the  water  thus  absorbed  is  saturated  with 
humate  of  lime  (the  most  soluble  of  the  hu- 
mates,  and  that  which  contains  the  largest 
proportion  of  humic  acid ;)  then  the  plants 
thus  nourished  would  not  receive  more  than 
330  Ibs.  of  humic  acid,  since  one  part  of 
humate  of  lime  requires  2500  parts  of  water 
for  solution. 

But  the  extent  of  land  which  we  have 
mentioned  produces  2843  Ibs.  of  corn  (in 
grain  and  straw,  the  roots  not  included,)  or 
22,000  Ibs.  of  beet  root  (without  the  leaves 
and  small  radicle  fibres.)  It  is  quite  evident 
thdL  the  330  Ibs.  of  humic  acid,  supposed  to 
bewbsorbed,  cannot  account  for  the  quantity 
of  carbon  contained  in  the  roots  and  leaves 
alone,  even  if  the  supposition  were  correct, 
that  the  whole  of  the  rainwater  was  ab- 
sorbed by  the  plants.  But  since  it  is  known 
that  only  a  small  portion  of  the  rainwater 
which  falls  upon  the  surface  of  the  earth 
evaporates  through  plants,  the  quantity  of 
carbon  which  can  be  conveyed  into  them  in 
any  conceivable  manner  by  means  of  humic 
acid  must  be  extremely  trifling,  in  compa- 
rison with  that  actually  produced  in  vege- 
tation. 

Other  considerations  of  a  higher  nature 
confute  the  common  view  respecting  the 
nutritive  office  of  humic  acid,  in  a  manner 
so  clear  and  conclusive  that  it  is  difficult  to 
conceive  how  it  could  have  been  so  gene- 
rally adopted. 

Fertile  land  produces  carbon  in  the  form 
of  wood,  hay,  grain,  and  other  kinds  of 
growth,  the  masses  of  which  differ  in  a  re- 
markable degree. 

2920  Ibs.  of  firs,  pines,  beeches,  &c.  grow 
as  wood  upon  one  Hessian  acre  of  forest 
land  with  an  average  soil.  The  same  super- 
Gees  yields  2755  Ibs.  of  hay. 

A  similar  surface  of  corn  land  gives  from 
19,000  to  22,000  Ibs.  of  beet  root,  or  881  Ibs. 
of  rye,  and  1961  Ibs.  of  straw,  160  sheaves 
of  15.4  Ibs.  each,— in  all,  2843  Ibs. 

One  hundred  parts  of  dry  fir  wood  con- 


tain 38  parts  of  carbon  ;  therefore,  2920  Ibj. 
contain  1109  Ibs.  of  carbon. 

One  hundred  parts  of  hay,*  dried  in  air, 
contain  44.31  parts  carbon.  Accordingly, 
2755  Ibs.  of  hay  contain  1111  Ibs.  of  carbon. 

Beet  rodts  contain  from  89  to  89.5  parts 
water,  and  from  10.5  to  11  parts  solid  mat- 
ter, which  consists  of  from  8  to  9  per  cent 
sugar,  and  from  2  to  2£  per  cent,  cellulai 
tissue.  Sugar  contains  42.4  per  cent ;  eel 
lular  tissue,  47  per  cent,  of  carbon. 

22,000  Ibs.  of  beet  root,  therefore,  if  they 
contain  9  per  cent,  of  sugar,  and  2  per  .cent 
of  cellular  tissue,  would  yield  1032  Ibs.  ol 
carbon,  of  which  833  Ibs.  would  be  due  to 
the  su^ar,  and  198  Ibs.  to  the  cellular  tissue; 
the  carbon  of  the  leaves  and  small  roots  not 
being  included  in  the  calculation. 

One  hundred  parts  of  straw,f  dried  in  air 
contain  38  per  cent,  of  carbon ;  therefore, 
1961  Ibs.  of  straw  contain  745  Ibs.  of  carbon. 
One  hundred  parts  of  corn  contain  43  parts 
of  carbon ;  882  Ibs  must,  therefore,  contain 
379  Ibs.— in  all,  1124  Ibs.  of  carbon. 

26,910  square  feet  of  wood  and  meadow 
land  produce,  consepuently,  1109  Ibs.  of 
carbon ;  while  the  same  extent  of  arable  land 
yields  in  beet  root,  without  leaves,  1032  Ibs., 
or  in  corn,  1124  Ibs. 

It  must  be  concluded  from  these  incon- 
testable facts,  that  equal  surfaces  of  cu.ti- 
vated  land  of  an  average  fertility  produce 
equal  quantities  of  carbon;  yet,  how  unlike 
have  been  the  different  conditions  of  the 
growth  of  the  plants  from  which  this  has 
been  deduced! 

Let  us  now  inquire  whence  the  grass  in 
a  meadow,  or  the  wood  in  a  forest,  receives 
its  carbon,  since  there  no  manure — no  car- 
bon— has  been  given  to  it  as  nourishment  ? 
and  how  it  happens,  that  the  soil,  thus  ex- 
hausted, instead  of  becoming  poorer,  be- 
comes every  year  richer  in  this  element  ? 

A  certain  quantity  of  carbon  is  taken 
every  year  from  the  forest  or  meadow,  in 
the  form  of  wood  or  hay,  and,  in  spite  of 
this,  the  quantity  of  carbon  in  the  soil  aug- 
ments ;  it  becomes  richer  in  humus. 

It  is  said  that  in  fields  and  orchards  all 
the  carbon  which  may  have  been  taken 
away  as  herbs,  as  straw,  as  seeds,  or  as 
fruit,  is  replaced  by  means  of  manure  ;  and 
yet  this  soil  produces  no  more  carbon  than 
that  of  the  forest  or  meadow,  where  it  is 
never  replaced.  It  cannot  be  conceived  that 
the  laws  for  the  nutrition  of  plants  are 
changed  by  culture, — that  the  sources  of 


*  100  parts  of  hay;  dried  at  lOo"  ^.  (212°  F.)and 
burned  with  oxide  of  copper  in  a  stream  of  oxygen 
gas,  yielded  51.93  water,  165.8  carbonic  acid,  and 
6.82  of  ashes.  This  gives  45  87  carbon.  5.76  hy- 
drogen, 31.55  oxygen,  and  6.82  ashes.  Hay,  dried 
in  the  air,  loses  11.2  p.  c.  water  at  100°  C.  (212 
F.)— (Dr.  Will.) 

t  Straw  analyzed  in  the  same  manner,  and  dried 
at  100°  C.,  gave  46.37  p.  c.  of  carbon,  5.68  p.  c.  of 
hydrogen,  43.93  p.  c.  of  oxygen,  and  4.02  p.  c.  of 
ashes.  Straw  dried  in  the  air  at  100°  C.  lost  18  p. 
c.  of  water.— Dr.  Will. 


OXYGEN   AND   CARBON. 


carbon  for  fruit  or  grain,  and  for  grass  or 
trees,  are  different. 

It  is  not  denied  that  manure  exercises  an 
influence  upon  the  development  of  plants  ; 
but  it  may  be  affirmed  with  positive  cer- 
tainty, that  it  neither  serves  for  the  produc- 
tion of  the  carbon,  nor  has  any  influence 
upon  it,  because  we  find  that  the  quantity 
of  carbon  produced  by  manured  lands  is 
not  greater  than  that  yielded  by  lands  which 
are  not  manured.  The  discussion  as  to  the 
manner  in  which  manure  acts  has  nothing 
to  do  with  the  present  question,  which  is, 
the  origin  of  the  carbon.  The  carbon  must 
be  derived  from  other  sources ;  and  as  the 
soil  does  not  yield  it,  it  can  only  be  ex- 
tracted from  the  atmosphere. 

In  attempting  to  explain  the  origin  of 
carbon  in  plants,  it  has  never  been  con- 
sidered that  the  question  is  intimately  con- 
nected with  that  of  the  origin  of  humus.  It 
is  universally  admitted  that  humas  arises 
from  the  decay  of  plants.  No  primitive 
hurnus,  therefore,  can  have  existed — for 
plants  must  have  preceded  the  humus. 

Now,  whence  did  the  first  vegetables  de- 
rive their  carbon  ?  and  in  what  form  is  the 
carbon  contained  in  the  atmosphere  ? 

These  two  questions  involve  the  conside- 
ration of  two  most  remarkable  natural  phe- 
nomena, which  by  their  reciprocal  and  un- 
interrupted influence  maintain  the  life  of  the 
individual  animals  and  vegetables,  and  the 
continued  existence  of  both  kingdoms  of  or- 
ganic nature. 

One  of  these  questions  is  connected  with 
the  invariable  condition  of  the  air  with  re- 
spect to  oxygen.  One  hundred  volumes  of 
air  have  been  found,  at  every  period  and  in 
every  climate,  to  contain  21  volumes  of 
oxygen,  with  such  small  deviations  that  they 
must  be  ascribed  to  errors  of  observation. 

Although  the  absolute  quantity  of  oxygen 
contained  in  the  atmosphere  appears  very 
great  when  represented  by  numbers,  yet  it 
is  not  inexhaustible.  One  man  consumes 
by  respiration  25  cubic  feet  of  oxygen  in 
2£  hours;  10  cwt.  of  charcoal  consume 
32,066  cubic  feet  of  oxygen  during  its  com- 
bustion; and  a  small  town,  like  Giessen, 
(with  about  7000  inhabitants)  extracts  yearly 
from  the  air,  by  the  wood  employed  as  fuel, 
more  than  551  millions  of  cubic  feet  of  this 
gas. 

When  we  consider  facts  such  as  these, 
our  former  statement,  that  the  quantity  of 
oxygen  in  the  atmosphere  does  not  diminish 
in  the  course  of  ages* — that  the  air  at  the 
present  day,  for  example,  does  not  contain 
less  oxygen  than  that  found  in  jars  buried 


*  If  the  atmosphere  possessed,  in  its  whole  ex- 
•  tent,  the  same  density  as  it  does  on  the  surface 
of  the  sea,  it  would  have  a  height  of  24,555 
Parisian  feet ;  but  it  contains  the  vapour  of  water, 
BO  that  we  may  assume  its  height  to  be  one  geo- 
graphical mile  =22,843  Parisian  feet.  Now  the 
radius  of  the  earth  is  equal  to  860  geographical 
miles ;  hence  the 


for  1800  years  in  Fompeii—  appears  quite 
incomprehensible,  unless  some  source  exists 
whence  the  oxygen  abstracted  is  replaced. 
How  does  it  happen,  then,  that  the  propor- 
tion of  oxygen  in  the  atmosphere  is  thus 
invariable  ? 

The  answer  to  this  question  depends  upon 
another;  namely,  what  becomes  of  the  car- 
bonic acid,  which  is  produced  during  the 
respiration  of  animals,  and  by  the  process 
of  combustion!  A  cubic  foot  of  oxygen 
gas,  by  uniting  wifn  carbon  so  as  to  form 
carbonic  acid,  does  not  change  its  volume. 
The  billions  of  cubic  feet  of  oxygen  ex- 
tracted from  the  atmosphere,  produce  the 
same  number  of  billions  of  cubic  feet  of 
carbonic  acid,  which  immediately  supply  its 
place. 

The  most  exact  and  most  recent  experi 
meats  of  De  Saussure,  made  in  every  sea- 
son for  a  space  of  three  years,  have  shown, 
that  the  air  contains  on  an  average  0-000415 
of  its  own  volume  of  carbonic  acid  gas ;  so 
that,  allowing  for  the  inaccuracies  of  the 
experiments,  which  must  diminish  the 
quantity  obtained,  the  proportion  of  carbonic 
acid  in  the  atmosphere  may  be  regarded  as 
nearly  equal  to  1-1000  part  of  its  weight. 
The  quantity  varies  according  to  the  sea 
sons ;  but  the  yearly  average  remains  con- 
tinually the  same. 

We  have  no  reason  to  believe  that  this 
proportion  was  less  in  past  ages ;  and  never- 
theless, the  immense  masses  of  carbonic 
acid  which  annually  flow  into  the  atmos- 
phere from  so  many  causes,  ought  percepti- 
bly to  increase  its  quantity  from  year  to 
year.  But  we  find  that  all  earlier  observers 
describe  its  volume  as  from  one-half  to  ten 
times  greater  than  that  which  it  has  at  the 
present  time ;  so  that  we  can  hence  at  most 
conclude  that  it  has  diminished. 

It  is  quite  evident  that  the  quantities  of 
carbonic  acid  and  oxygen  in  the  atmosphere, 
which  remain  unchanged  by  lapse  of  lime, 
must  stand  in  some  fixed  relation  to  one 
another;  a  cause  must  exist  which  prevents 
the  increase  of  carbonic  acid  by  removing 
that  which  is  constantly  forming;  and  there 

Volume  of  atmosphere  =9, 307, 500  cubic  miles. 

=  cube  of  210-4  miles. 
Volume  of  oxygen        =1,954,578  cubic  miles. 

=  cube  of  125  miles. 

Vol.  of  carbonic  acid    =3,8627  cubic  miles. 
=  cube  of  15'7  miles. 

The  maximum  of  the  carbonic  acid  contained 
in  the  atmosphere  has  not  here  been  adopted,  but 
the  mean,  which  is  equal  to  0  000415. 

A  man  daily  consumes  45,000  cubic  inches 
(Parisian.)  A  man  yearly  consumes  9505'2  cubic 
feet.  100  million  men  yearly  consume  9,505,- 
200,000,000  cubic  feet. 

Hence  a  thousand  million  men  yeaily  consume 
0'79745  cubic  miles  of  oxygen.  But  the  air  is 
rendered  incapable  of  supporting  the  process  of 
respiration,  when  the  quantity  of  its  oxygen  is 
decreased  12  per  cent. ;  so  that  a  thousand  million 
men  would  make  the  air  unfit  for  respiration  in  a 
million  years.  The  consumption  of  oxygen  by 
animals,  and  by  the  process  of  combustion,  is  not 
introduced  into  the  calculation. 


AGRICULTURAL    CHEMISTRY. 


must  be  some  means  of  replacing  the  oxy- 
gen, which  is  removed  from  the  air  by 
the  processes  of  combustion  and  putre- 
faction, as  well  as  by  the  respiration  of 
anmials. 

Both  these  causes  are  united  in  the  pro- 
cess of  vegetable  life. 

The  facts  which  we  have  stated  in  the 
preceding  pages  prove  that  the  carbon  of 
plants  must  be  derived  exclusively  from  the 
atmosphere.  Now,  carbon  exists  in  the 
atmosphere  only  in  the  form  of  carbonic 
acid,  and  therefore,  in  a  state  of  combination 
with  oxygen. 

It  has  been  already  mentioned  likewise, 
that  carbon  and  the  elements  of  water  form 
the  principal  constituents  of  vegetables;  the 
quantity  of  the  substances  which  do  not 
possess  this  composition  being  in  a  very 
small  proportion.  Now,  the  relative  quan- 
tity of  oxygen  in  the  whole  mass  is  less  than 
in  carbonic  acid  ;  for  the  latter  contains  two 
equivalents  of  oxygen,  while  one  only  is 
required  to  unite  with  hydrogen  in  the  pro- 
portion to  form  water.  The  vegetable  pro- 
ducts which  contain  oxygen  in  larger  pro- 
portion than  this,  are,  comparatively,  few  in 
number;  indeed,  in  many  the  hydrogen  is  in 
great  excess.  It  is  obvious,  that  when  the 
hydrogen  of  water  is  assimilated  by  a  plant, 
the  oxygen  in  combination  with  it  must  be 
liberated,  and  will  afford  a  quantity  of  this 
t  lament  sufficient  for  the  wants  of  the  plant, 
li'  tins  be  the  case,  the  oxygen  contained  in 
the  carbonic  acid  is  quite  unnecessary  in  the 
process  of  vegetable  nutrition,  and  it  will 
consequently  escape  into  the  atmosphere  in 
a  gaseous  form.  It  is,  therefore,  certain,  that 
plants  must  possess  the  power  of  decom- 
posing carbonic  acid,  since  they  appropriate 
its  carbon  for  their  own  use.  The  forma- 
tion of  their  principal  component  substances 
must  necessarily  be  attended  with  the  sepa- 
ration of  the  carbon  of  the  carbonic  acid 
from  the  oxygen,  which  must  be  returned  to 
the  atmosphere,  while  the  carbon  enters 
into  combination  with  water  or  its  elements. 
The  atmosphere  must  thus  receive  a  volume 
of  oxygen  for  every  volume  of  carbonic 
acid  which  has  been  decomposed. 

This  remarkable  property  of  plants  has 
been  demonstrated  in  the  most  certain  man- 
ner, and  it  is  in  the  power  of  every  person 
to  convince  himself  of  its  existence.  The 
leaves  and  other  green  parts  of  a  plant  ab- 
sorb carbonic  acid,  and  emit  an  equal 
volume  of  oxygen.  They  possess  this  pro- 
perty quite  independently  of  the  plant;  for  if, 
after  being  separated  from  the  stem,  they  are 
placed  in  water  containing  carbonic  acid, 
and  exposed  in  that  condition  to  the  sun's 
light,  the  carbonic  acid  is,  after  a  time, 
found  to  have  disappeared  entirely  from  the 
water.  If  the  experiment  is  conducted  un- 
der a  glass  receiver  filled  with  water,  the 
oxygen  emitted  from  the  plant  may  be  col- 
ected  and  examined.  When  no  more  oxy- 
,gen  gas  is  evolved,  it  is  a  sign  that  all  the 
dissolved  carbonic  acid  is  decomposed ;  but 


the  operation  recommences  if  a  new  portion 
of  it  is  added. 

Plants  do  not  emit  gas  when  placed  in 
water  which  either  is  free  from  carbonic 
acid,  or  contains  an  alkali  that  protects  it 
from  assimilation. 

These  observations  were  first  made  by 
Priestly  and  Sennebier.  The  excellent  ex- 
periments of  De  Saussure  have  farther 
shown,  that  plants  increase  in  weight  dur- 
ing the  decomposition  of  carbonic  acid  and 
separation  of  oxygen.  This  increase  in 
weight  is  greater  than  can  be  accounted  for 
by  the  quantity  of  carbon  assimilated  ;  a  fact 
which  confirms  the  view,  that  the  elements 
of  water  are  assimilated  at  the  same  time. 

The  life  of  plants  is  closely  connected 
with  that  of  animals,  in  a  most  simple  man- 
ner, and  for  a  wise  and  sublime  purpose. 

The  presence  of  a  rich  and  luxuriant  vege- 
tation may  be  conceived  without  the  con- 
currence of  animal  life,  but  the  existence  of 
animals  is  undoubtedly  dependent  upon  the 
life  and  development  of  plants. 

Plants  not  only  afford  the  means  of  nutri- 
tion for  the  growth  and  continuance  of  ani- 
mal organization,  but  they  likewise  furnish 
that  which  is  essential  for  the  support  of  the 
important  vital  process  of  respiration ;  for, 
besides  separating  all  noxious  matters  from 
the  atmosphere,  they  are  an  inexhaustible 
source  of  pure  oxygen,  which  supplies  the 
loss  which  the  air  is  constantly  sustaining. 
Animals  on  the  other  hand  expire  carbon, 
which  plants  inspire;  and  thus  the  compo- 
sition of  the  medium  in  which  both  exist, 
namely,  the  atmosphere,  is  maintained  con- 
stantly unchanged. 

It  may  be  asked — is  the  quantity  of  car- 
bonic acid  in  the  atmosphere,  which  scarcely 
amounts  to  1-1  Oth  per  cent.,  sufficient  for 
the  wants  of  the  whole  vegetation  on  the 
surface  of  the  earth, — is  it  possible  that  the 
carbon  of  plants  has  its  origin  from  the  air 
alone?  This  question  is  very  easily  an- 
swered. It  is  known,  that  a  column  of  air 
of  2441  Ibs!  weight  rests  upon  every  square 
Hessian  foot  (=0.567  square  foot  English) 
of  the  surface  of  the  earth ;  the  diameter  of 
the  earth  and  its  superficies  are  likewise 
known,  so  that  the  weight  of  the  atmosphere 
can  be  calculated  with  the  greatest  exactness. 
The  thousandth  part  of  this  is  caroonic  acid, 
which  contains  upwards  of  27  per  cent,  car- 
bon. By  this  calculation  it  can  be  shown, 
that  the  atmosphere  contains  3306  billion 
Ibs.  of  carbon  ;  a  quantity  which  amounts  to 
more  than  the  weight  of  all  the  plants,  and 
of  all  the  strata  of  mineral  and  brown  coal, 
which  exist  upon  tne  earth.  This  carbon 
is,  therefore,  more  than  adequate  to  all  the 
purposes  for  which  it  is  required.  The 
quantity  of  carbon  contained  in  seawater  is 
proportionally  still  greater. 

If,  for  the  sake  of  argument,  we  suppose 
the  superficies  of  the  leaves  and  other  green, 
parts  of  plants,  by  which  the  absorption  of 
carbonic  acid  is  effected,  to  be  double  that  of 
the  soil  upon  which  they  grow,  a  supposi 


ASSIMILATION  OF  CARBON. 


17 


tion  which  is  mucn  under  the  truth  in  the 
case  of  woods,  meadows,  and  corn  fields  ; 
and  if  we  farther  suppose  that  carbonic  acid 
equal  to  0.00067  of  the  volume  of  the  air, 
or  1-1 000th  of  its  weight  is  abstracted  from 
it  during  every  second  of  time,  for  eight 
hours  daily,  by  a  field  of  53,814  square  feet 
(==  2  Hessian  acres  ;)  then  those  leaves 
would  receive  1102  Ibs.  of  carbon  in  two 
aundred  days.* 

But  it  is  inconceivable,  that  the  functions 
of  the  organs  of  a  plant  can  cease  for  any 
one  moment  during  its  life.  The  roots  and 
other  parts  of  it,  which  possess  the  same 
power,  absorb  constantly  water  and  carbonic 
acid.  This  power  is  independent  of  solar 
light.  During  the  day,  when  the  plants  are 
in  the  shade,  and  during  the  night,  carbonic 
acid  is  accumulated  in  all  parts  of  their 
structure ;  and  the  assimilation  of  the  carbon 
and  the  exhalation  of  oxygen  commence 
from  the  instant  that  the  rays  of  the  sun 
strike  them.  As  soon  as  a  young  plant 
breaks  through  the  surface  of  the  ground, 
it  begins  to  acquire  colour  from  the  top 
downwards  ;  and  the  true  formation  of 
woody  tissue  commences  at  the  same  time. 

The  proper,  constant,  and  inexhaustible 
sources  of  oxygen  gas  are  the  tropics  and 
warm  climates,  where  a  sky,  seldom  cloud- 
ed, permits  the  glowing  rays  of  the  sun  to 
shine  upon  an  immeasurably  luxuriant  ve- 
getation. The  temperate  and  cold  zones, 
where  artificial  warmth  must  replace  defi- 
cient heat  of  the  sun,  produce,  on  the  con- 
trary, carbonic  acid  in  superabundance, 
which  is  expended  in  the  nutrition  of  the 
tropical  plants.  The  same  stream  of  air, 
which  moves  by  the  revolution  of  the  earth 
from  the  equator  to  the  poles,  brings  to  us 
in  its  passage  from  the  equator,  the  oxygen 
generated  there,  and  carries  away  the  car- 
bonic acid  formed  during  our  winter. 

The  experiments   of  De  Saussure  have 

*  The  quantity  of  carbonic  acid  which  can  be  ex- 
tracted from  the  air  in  a  given  time,  is  shown  by 
the  following  calculation.  During  the  whitewash- 
ing of  a  small  chamber,  the  superficies  of  the 
walls  and  roof  of  which  we  will  suppose  to  be  105 
square  metres,  and  which  receives  six  coats  of 
lime  in  four  days,  carbonic  acid  is  abstracted  from 
the  air,  and  the  lime  is  consequently  converted, 
on  the  surface,  into  a  carbonate.  It  has  been  ac- 
curately determined  that  one  square  decimetre  re- 
ceives in  this  way,  a  coating  of  carbonate  of  lime 
which  weighs  0.732  grammes.  Upon  the  105 
square  metres  already  mentioned  there  must  ac- 
cordingly He  formed  7686  grammes  of  carbonate 
of  lime,  which  contain  4325.6  grammes  of  carbo- 
nic acid.  The  weight  of  one  cubic  decimetre  of 
carbonic  acid  being  calculated  at  two  grammes, 
(more  accurately  1.97973.)  the  above  mentioned 
surface  must  absorb  in  four  days  2.163  cubic  me- 
tres of  carbonic  acid.  2500  square  metres  (one 
Hessian  acre)  would  absorb,  under  a  similar  treat- 
ment, 51  i  cubic  metres=1818  cubic  feet  of  car- 
bonic acid  in  four  days.  In  200  days  it  would  ab- 
sorb 2575  cubic  metres=  904,401  cubic  feet,  which 
contain  11,353  Ibs.  of  carbonic  acid,  of  which  3304 
Ibs.  are  carbon,  a  quantity  three  times  as  great  as 
that  which  is  assimilated  by  the  leaves  and  roots 
growing  upon  the  same  space. 


proved,  that  the  upper  strata  of  the  air  con- 
tain more  carbonic  acid  than  the  lower, 
which  are  in  contact  with  plants  ;  and  that 
the  quantity  is  greater  by  night  than  by  day, 
when  it  undergoes  decomposition. 

Plants  thus  improve  the  air  by  the  remo- 
val of  carbonic  acid,  and  by  the  renewal  of 
oxygen,  which  is  immediately  applied  to 
the  use  of  man  and  animals.  The  horizon- 
tal currents  of  the  atmosphere  bring  with 
them  as  much  as  they  carry  away,  and  the 
interchange  of  air  between  the  upper  and 
lower  strata,  which  their  difference  of  tem- 
perature causes,  is  extremely  trifling  when 
compared  with  the  horizontal  movements 
of  the  winds.  Thus  vegetable  culture 
heightens  the  healthy  state  of  a  country, 
and  a  previously  healthy  country  would  be 
rendered  quite  uninhabitable  by  the  cessa- 
tion of  all  cultivation. 

The  various  layers  of  wood  and  mineral 
coal,  as  well  as  peat,  form  the  remains  of  a 
primeval  vegetation.  The  carbon  which 
they  contain  must  have  been  originally  in 
the  atmosphere  as  carbonic  acid  in  which 
form  it  was  assimilated  by  the  plants  which 
constitute  these  formations.  It  follows  from 
this,  that  the  atmosphere  must  be  richer  in 
oxygen  at  the  present  time  than  in  former 
periods  of  the  earth's  history.  The  increase 
must  be  exactly  proportional  to  the  quantity 
of  carbon  and  hydrogen  contained  in  these 
carboniferous  deposits.  Thus,  during  the 
formation  of  353  cubic  feet  of  Newcastle 
splint  coal,  the  atmosphere  must  have  re 
ceived  643  cubic  feet  of  oxygen  produced 
from  the  carbonic  acid  assimilated,  and  also 
158  cubic  feet  of  the  same  gas  resulting 
from  the  decomposition  of  water.  In  for 
mer  ages,  therefore,  the  atmosphere  must 
have  contained  less  oxygen,  but  a  much 
larger  proportion  of  carbonic  acid,  than  it 
does  at  the  present  time,  a  circumstance 
which  accounts  for  the  richness  and  luxuri- 
ance of  the  earlier  vegetation. 

But  a  certain  period  must  have  arrived  in 
which  the  quantity  of  carbonic  acid  con- 
tained in  the  air  experienced  neither  increase 
lor  diminution  in  any  appreciable  quantity. 
For  if  it  received  an  additional  quantity  to 
ts  usual  proportion,  an  increased  vegetation 
would  be  the  natural  consequence,  and  the 
excess  would  thus  be  speedily  removed. 
And,  on  the  other  hand,  if  the  gas  was  less 
than  the  normal  quantity,  the  progress 
of  vegetation  would  be  retarded,  and  the 
proportion  would  soon  attain  its  proper 
standard. 

The  most  important  function  in  the  life 
of  plants,  or,  in  other  words,  in  their  as- 
similation of  carbon,  is  the  separation,  we 
might  almost  say  the  generation^,  of  oxygen, 

matter  can  oe  considered  as  nutritious, 
or  as  necessary  to  the  growth  of  plants, 
which  possesses  a  composition  either  simi- 
ar  to  or  identical  with  theirs,  and  the  as- 
similation of  which,  therefore,  could  take 
alace  without  exercising  this  function.  The 
reverse  is  the  case  in  the  nutrition  of  ani 


18 


AGRICULTURAL    CHEMISTRY. 


mals.  Hence  such  substances  as  sugar, 
starch,  and  gum,  which  are  themselves  pro- 
ducts of  plants,  cannot  be  adopted  for  as- 
similation. And  this  is  rendered  certain  by 
the  experiments  of  vegetable  physiologists, 
who  have  shown  that  aqueous  solutions  of 
these  bodies  are  imbibed  by  the  roots  of 
plants,  and  carried  to  all  parts  of  their  struc- 
ture, but  are  not  assimilated,  they  cannot, 
therefore,  be  employed  in  their  nutrition. 
We  could  scarcely  conceive  a  form  more 
convenient  for  assimilation  than  that  of 
gum,  starch,  and  sugar,  for  they  ah  contain 
the  elements  of  woody  fibre,  and  nearly  in 
the  same  proportions. 

In  the  second  part  of  the  work  we  shall 
adduce  satisfactory  proofs  that  decayed 
woody  fibre  (humus')  contains  carbon  and 
the  elements  of  water,  without  an  excess  of 
oxygen  j  its  composition  differing  from  that 
of  woody  fibre  in  its  being  richer  in  carbon. 

Misled  by  this  simplicity  in  its  constitu- 
tion, physiologists  found  no  difficulty  in  dis- 
covering the  mode  of  the  formation  of 
Woody  fibre ;  for  they  say,*  humus  has  only 
to  enter  into  combination  with  water,  in 
order  to  effect  the  formation  of  woody  fibre, 
and  other  substances  similaily  composed, 
such  as  sugar,  starch,  and  gum.  But  they 
forget  that  their  own  experiments  have  suf- 
ficiently demonstrated  the  inaptitude  of  these 
substances  for  assimilation. 

All  the  erroneous  opinions  concerning  the 
modus  operandi  of  humus  have  their  origin 
m  the  false  notions  entertained  respecting 
the  most  important  vital  functions  of  plants ; 
analogy,  that  fertile  source  of  error,  having, 
unfortunately,  led  to  the  very  unapt  com- 
parison of  the  vital  functions  of  plants  with 
those  of  animals. 

Substances,  such  as  sugar,  starch,  &c., 
which  contain  carbon  and  the  elements  of 
water,  are  products  of  the  life  of  plants 
which  live  only  while  they  generate  them. 
The  same  mav  be  said  of  humus,  for  it  can 
be  formed  in  plants  like  the  former  sub- 
stances. Smithson,  Jameson,  and  Thomson, 
found  that  the  black  excretions  of  unhealthy 
elms,  oaks,  and  horse  chesnuts,  consisted  of 
humic  acid  in  combination  with  alkalies. 
Berzelius  detected  similar  products  in  the 
bark  of  .most  trees.  Now,  can  it  be  supposed 
that  the  diseased  organs  of  a  plant  possess 
the  power  of  generating  the  matter  to  which 
its  substance  and  vigour  are  ascribed? 

How  does  it  happen,  it  may  be  asked,  that 
the  absorption  of  carbon  from  the  atmos- 
phere by  plants  is  doubted  by  all  botanists 
and  vegetable  physiologists,  and  that  by  the 
greater  number  the  purification  of  the  air  by 
means  of  them  is  wholly  denied  ? 

The  action  of  plants  on  the  air  in  the 
absence  of  light,  that  is  during  night,  has 
been  much  misconceived  by  botanists,  and 
from  this  we  may  trace  most  of  the  errors 
which  abound  in  the  greater  part  of  their 
writings.  The  experiments  of  Ingenhouss 


•  Meyeu,  Ffanzenphysiologie,  II.,  S.  141. 


were  in  a  great  degree  the  cause  of  tms  un- 
certainty of  opinion  regarding  the  influence 
of  plants  in  purifying  the  air.  His  obser- 
vation that  green  plants  emit  carbonic  acid 
in  the  dark,  led  t)e  Saussure  and  Grischow 
to  new  investigations,  by  which  they  ascer- 
tained that  under  such  conditions  plants  do 
really  absorb  oxygen  and  emit  carbonic  acid ; 
but  that  the  whole  volume  of  air  undergoes 
diminution  at  the  same  time.  From"  the 
latter  fact  it  follows,  that  the  quantity  of 
oxygen  gas  absorbed  is  greater  than  the 
volume  of  carbonic  acid  separated ;  for,  if 
this  were  not  the  case,  no  diminution  could 
occur.  These  facts  cannot  be  doubted,  but 
the  views  based  on  them  have  been  so  false, 
that  nothing,  except  the  total  want  of  obser- 
vation and  the  utmost  ignorance  of  the 
chemical  relations  of  plants  to  the  atmos- 
phere, can  account  for  their  adoption. 

It  is  known  that  nitrogen,  hydrogen,  and 
a  number  of  other  gases,  exercise  a  pecu- 
liar, and  in  general,  an  injurious  influence 
upon  living  plants.  Is  it,  then,  probable,  that 
oxygen,  one  of  the  most  energetic  agents  in 
nature,  should  remain  without  influence  on 
plants  when  one  of  their  peculiar  processes 
of  assimilation  has  ceased  ? 

It  is  true  that  the  decomposition  of  car- 
bonic acid  is  arrested  by  absence  of  light. 
But  then,  namely,  at  night,  a  true  chemical 
process  commences,  in  consequence  of  the 
action  of  the  oxygen  in  the  aii,  upon  the 
organic  substances  composing  the  leaves, 
blossoms,  and  fruit.  This  process  is  not  at 
all  connected  with  the  life  of  the  vegetable 
organism,  because  it  goes  on  in  a  dead  plant 
exactly  as  in  a  living  one. 

The  substances  composing  the  leaves  of 
different  plants  being  known,  it  is  a  matter 
of  the  greatest  ease  and  certainty  to  calcu- 
late which  of  them,  during  life,  should  ab- 
sorb most  oxygen  by  chemical  action  when 
the  influence  of  light  is  withdrawn. 

The  leaves  and  green  parts  of  all  plants 
containing  volatile  oils  or  volatile  constitu- 
ents in  general,  which  change  into  resin  by 
the  absorption  of  oxygen,  should  absorb 
more  than  other  parts  which  are  free  from 
such  substaruces.  Those  leaves,  also,  which 
contain  either  the  constituents  of  nutgails, 
or  compounds  in  which  nitrogen  is  present, 
ought  to  absorb  more  oxygen  than  those 
which  do  not  contain  such  matters.  The 
correctness  of  these  inferences  has  been  dis- 
tinctly proved  by  the  observations  of  De 
Saussure ;  for,  while  the  tasteless  leaves  of 
the  Jlgave  americana  absorb  only  0-3  of 
their  volume  of  oxygen  in  the  dark,  during 
24  hours,  the  leaves  of  the  Pinus  Jlbies, 
which  contain  volatile  and  resinous  oils, 
absorb  10  times,  those  of  the  Quercm  Robur 
containing  tannic  acid  14  times,  and  the 
balmy  leaves  of  the  Popiihts  alba  21  times 
that  quantity.  This  chemical  action  is 
shown  very  plainly  also,  in  the  leaves  of 
the  Cotyledon  calycinum,  the  Cacaliaficoidej, 
and  others;  for  they  are  sour  like  sorrel  in 
the  morning,  tasteless  at  noon,  and  bitter  in 


ASSIMILATION  OF  CARBON. 


the  evening.  The  formation  of  acids  is 
effected  during  the  night  by  a  true  process 
of  oxidation :  these  are  deprived  of  their 
acid  properties  during  the  day  and  evening, 
and  are  changed  by  separation  of  a  part  of 
their  oxygen  into  compounds  containing 
oxygen  and  hydrogen,  either  in  the  same 
proportions  as  in  water,  or  even  with  an 
excess  of  hydrogen,  which  is  the  composi- 
tion of  all  tasteless  and  bitter  substances. 

Indeed,  the  quantity  of  oxygen  absorbed 
could  be  estimated  pretty  nearly  by  the  dif- 
ferent periods  which  the  green  leaves  of 
plants  require  to  undergo  alteration  in  colour, 
by  the  influence  of  the  atmosphere.  Those 
which  continue  longest  green  will  abstract 
less  oxygen  from  the  air  in  an  equal  space 
of  time,  than  those  the  constituent  parts  of 
which  suffer  a  more  rapid  change.  It  is 
found,  for  example,  that  the  leaves  of  the 
Ilex  aquifoliiim,  distinguished  by  the  dura- 
bility of  their  colour,  absorb  only  O86  of 
their  volume  of  oxygen  gas  in  the  same  time 
that  the  leaves  of  the  poplar  absorb  8,  and 
those  of  the  beech  9$  times  their  volume ; 
both  the  beech  and  poplar  being  remarkable 
for  the  rapidity  and  ease  with  which  the 
colour  of  their  leaves  changes. 

When  the  green  leaves  of  the  poplar,  the 
beech,  the  oak,  or  the  holly,  are  dried  under 
the  air  pump,  with  exclusion  of  light,  then 
moistened  with  water,  and  placed  under  a 
glass  globe  filled  with  oxygen,  they  are 
found  to  absorb  that  gas  in  proportion  as 
they  change  in  colour.  The  chemical  nature 
of  this  process  is  thus  completely  established. 
The  diminution  of  the  gas  which  occurs  can 
only  be  owing  to  the  union  of  a  large  pro- 
portion of  oxygen  with  those  substances 
which  are  already  in  the  state  of  oxides,  or 
to  the  oxidation  of  the  hydrogen  in  those 
vegetable  compounds  which  contain  it  in 
excess.  The  fallen  brown  or  yellow  leaves 
of  the  oak  contain  no  longer  tannin,  and 
those  of  the  poplar  no  balsamic  constituents. 

The  property  which  green  leaves  possess 
of  absorbing  oxygen  belongs  also  to  fresh 
wood,  \vhether  taken  from  a  twig  or  from 
the  interior  of  the  trunk  of  a  tree.  When 
fine  chips  of  such  wood  are  placed  in  a 
moist  condition  under  a  jar  filled  with  oxy- 
cren,  the  gas  is  seen  to  diminish  in  volume. 
But  wood,  dried  by  exposure  to  the  atmo- 
sphere and  then  moistened,  converts  the 
oxygen  into  carbonic  acid,  without  change 
of  volume ;  fresh  wood,  therefore,  absorbs 
most  oxygen. 

MM.  Peiersen  and  SchSdler  have  shown, 
by  the  careful  elementary  analysis  of  24  dif- 
ferent kinds  of  wood,  that  they  contain  car- 
bon and  the  elements  of  water,  with  the 
addition  of  a  certain  quantity  of  hydrogen. 
Oak  wood,  recently  taken  from  the  tree,  and 
dried  at  100°  C.  (212  F.,)  contains  49,432 
carbon,  6.069  hydrogen,  and  44.499  oxygen. 

The  proportion  of  hydrogen  which  is  ne- 
cessary to  combine  with  44.498  oxygen  in 
order  to  form  water,  is  •£•  of  this  quantity, 
namely,  5.56 ;  it  is  evident,  therefore,  that 


oak  wood  contains  ^  more  hydrogen  than 
corresponds  to  this  proportion.  In  Pinus 
Larix,  P.  Mies,  and  P.  picea  the  excess  of 
hydrogen  amounts  to  \,  and  in  Tilia  euro- 
pcua  to  £.  The  quantity  of  hydrogen  sta  nds 
m  some  relation  to  the  specific  weight  of  the 
wood;  the  lighter  kinds  of  wood  contain 
more  of  it  than  the  heavier.  In  ebony  wood 
(Diospyros  Ebenum)  the  oxygen  and'hydro- 
gen  are  in  exactly  the  same  proportion  as  in 
water. 

The  difference  between  the  composition 
of  the  varieties  of  wood,  and  that  of  simple 
woody  fibre,  depends,  unquestionably,  upon 
the  presence  of  constituents,  in  part  soluble, 
and  in  part  insoluble,  such  as  resin  and 
other  matters,  which  contain  a  large  pro- 
portion of  hydrogen:  the  hydrogen  of  such 
substances  being  in  the  analysis  of  the  vari- 
ous woods  superadded  to  that  of  the  true 
woody  fibre. 

It  has  previously  been  mentioned  that 
mouldering  oak  wood  contains  carbon  and 
the  elements  of  water,  without  any  excess 
of  hydrogen.  But  the  proportions  of  iu 
constituents  must  necessarily  have  been  dif- 
ferent, if  the  volume  of  the  air  had  not 
changed  during  its  decay,  because  the  pro- 
portion of  hydrogen  in  those  component 
substances  of  the  wood  which  contained  it 
in  excess  is  here  diminished,  and  this  dimi- 
nution could  only  be  effected  by  an  absorp- 
tion of  oxygen,  and  consequent  formation 
of  water. 

Most  vegetable  physiologists  have  con- 
nected the  emission  of  carbonic  acid  during 
the  night  with  the  absorption  of  oxygen 
from  the  atmosphere,  and  have  considered 
these  actions  as  a  true  process  of  respiration 
in  plants,  similar  to  that  of  animals,  and  like 
it,  having  for  its  result  the  separation  of 
carbon  from  some  of  their  constitutents. 
This  opinion  has  a  very  weak  and  unstable 
foundation. 

The  carbonic  acid,  which  has  been  ab- 
sorbed by  the  leaves  and  by  the  roots,  to- 
gether with  water,  ceases  to  be  decomposed 
on  the  departure  of  daylight ;  it  is  dissolved 
in  the  juices  which  pervade  all  parts  of  the 
plant,  and  escapes  every  moment  through 
the  leaves  in  quantity  corresponding  to  that 
of  the  water  which  evaporates. 

A  soil  in  which  plants  vegetate  vigor- 
ously, contains  a  certain  quantity  of  mois- 
ture which  is  indispensably  necessary  to 
their  existence.  Carbonic  acid,  likewise,  i;» 
always  present  in  such  a  soil,  whether  it 
has  been  abstracted  from  the  air  or  has1  been 
generated  by  the  decay  of  vegetable  matter. 
Rain  and  wellwater,  and  also  that  from 
other  sources,  invariably  contains  carbonic 
acid.  Plants  during  their  life  constantly 
possess  the  power  of  absorbing  by  their 
roots  moisture,  and,  along  with  it,  air  and 
carbonic  acid.  Is  it,  therefore,  surprising 
that  the  carbonic  acid  should  be  returned 
unchanged  to  the  atmosphere,  along  with 
water,  when  light  (the  cause  of  the  fixation 
of  its  carbon)  is  absent? 


AGRICULTURAL    CHEMISTRY. 


Neither  this  emission  of  carbonic  acid  nor 
the  absorption  of  oxygen  has  any  connection 
with  the  process  of  assimilation;  nor  have 
they  the  slightest  relation  to  one  another; 
the  one  .s  a  purely  mechanical,  the  other  a 
purely  chemical  process.  A  cotton  wick, 
inclosed  in  a  lamp,  which  contains  a  liquid 
saturated  with  carbonic  acid,  acts  exactly  in 
the  same  manner  as  a  living  plant  in  the 
night.  Water  and  carbonic  acid  are  sucked 
up  by  capillary  attraction,  and  both  evapo- 
rate from  the  exterior  part  of  the  wick. 

Plants  which  live  in  a  soil  containing  hu- 
mus exhale  much  more  carbonic  acid  dur- 
jig  the  night  than  those  which  grow  in  dry 
situations ;  they  also  yield  more  in  rainy 
than  in  dry  weather.  These  facts  point  out 
to  us  the  cause  of  the  numerous  contradic- 
tory observations,  which  have  been  made 
with  respect  to  the  change  impressed  upon 
the  air  by  living  plants,  both  in  darkness 
and  in  common  daylight,  but  which  are  un- 
worthy of  consideration,  as  they  do  not 
assist  in  the  solution  of  the  main  question. 

There  are  other  facts  which  prove  in  a  de- 
cisive manner  that  plants  yield  more  oxygen 
to  the  atmosphere  than  they  extract  from  it; 
these  proofs,  however,  are  to  be  drawn  with 
certainty  only  from  plants  which  live  under 
water. 

When  pools  and  ditches,  the  bottoms  of 
which  are  covered  with  growing  plants, 
freeze  upon  their  surface  in  winter,  so  that 
the  water  is  completely  excluded  from  the 
atmosphere  by  a  clear  stratum  of  ice,  small 
bubbles  of  gas  are  observed  to  escape,  con- 
tinually, during  the  day,  from  the  points  of 
the  leaves  and  twigs.  These  bubbles  are 
seen  most  distinctly  when  the  rays  of  the 
sun  fall  upon  the  ice;  they  are  very  small 
at  first,  but  collect  under  the  ice  and  form 
larger  bubbles.  They  consist  of  pure  oxy- 
gen gas.  Neither  during  the  night,  nor  dur- 
ing the  day  when  the  sun  does  not  shine, 
are  they  observed  to  diminish  in  quantity. 
The  source  of  this  oxygen  is  the  carbonic 
acid  dissolved  in  the  water,  which  is  ab- 
sorbed by  the  plants,  but  is  again  supplied 
to  the  water,  by  the  decay  of  vegetable  sub- 
stances contained  in  the  soil.  If  these  plants 
absorb  oxygen  during  the  night,  it  can  be  in 
no  greater  quantity  than  that  which  the  sur- 
rounding water  holds  in  solution,  for  the 
gas,  which  has  been  exhaled,  is  not  again 
absorbed.  The  action  of  water  plants  can- 
not be  supposed  to  form  an  exception  to  a 
great  law  of  nature,  and  the  less  so,  as  the 
different  action  of  aerial  plants  upon  the  at- 
mosphere is  very  easily  explained. 

The  opinion  is  not  new  that  the  carbonic 
acid  of  the  air  serves  for  the  nutriment  of 
plants,  and  that  its  carbon  is  assimilated  by 
them ;  it  has  been  admitted,  defended,  and 
argued  for,  by  the  soundest  and  most  intelli- 
gent natural  philosophers,  namely,  by  Priest- 
ley, Sennebier,  De  Saussure,  and  even  by 
Ingenhouss  himself.  There  scarcely  exists 
a  theory  in  natural  science,  in  favour  of 
which  there  are  mo  \lear  and  decisive  ar- 


guments. How,  then,  are  we  to  account 
for  its  not  being  received  in  its  full  extent  by 
most  other  physiologists,  for  its  being  even 
disputed  by  many,  and  considered  by  a  few 
as  quite  refuted  ! 

All  this  is  due  to  two  causes,  which  we 
shall  now  consider. 

One  is,  that  in  botany  the  talent  and  la- 
bour of  inquirers  has  been  wholly  spent  in 
the  examination  of  form  and  structure :  che- 
mistry and  physics  have  not  been  allowed 
to  sit  in  council  upon  the  explanation  of  the 
most  simple  processes ;  their  experience  and 
their  laws  have  not  been  employed,  though 
the  most  powerful  means  of  help  in  the  ac- 
quirement of  true  knowledge.  They  have 
not  been  used,  because  their  study  has  been 
neglected. 

All  discoveries  in  physics  and  in  chemis- 
try, all  explanations  of  chemists,  must  re- 
main without  fruit  and  useless,  because, 
even  to  the  great  leaders  in  physiology,  car- 
bonic acid,  ammonia,  acids,  and  bases,  are 
sounds  without  meaning,  words  without 
sense,  terms  of  an  unknown  language,  which 
awaken  no  thoughts  and  no  associations. 
They  treat  these  sciences  like  the  vulgar, 
who  despise  a  foreign  literature  in  exact 
propoUion  to  their  ignorance  of  it;  since 
even  when  they  have  had  some  acquintance 
with  them,  they  have  not  understood  their 
spirit  and  application. 

Physiologists  reject  the  aid  of  chemistry 
in  their  inquiry  into  the  secrets  of  vitality, 
although  it  alone  could  guide  them  in  the 
true  path  ;  they  reject  chemistry,  because  in 
its  pursuit  of  knowledge  it  destroys  the  sub- 
jects of  its  investigation ;  but  they  forget 
that  the  knife  of  the  anatomist  must  dis- 
member the  body,  and  destroy  its  organs,  if 
an  account  is  to  be  given  of  their  form, 
structure,  and  functions. 

When  pure  potato  starch  is  dissolved  in 
nitric  acid,  a  ring  of  the  finest  wax  remains. 
What  can  be  opposed  to  the  conclusion  of 
the  chemist,  that  each  grain  of  starch  con- 
sists of  concentric  layers  of  wax  and  amylin, 
which  thus  mutually  protect  each  other 
against  the  action  of  water  and  ether'?  Can 
results  of  this  kind,  which  illustrate  so  com- 
pletely both  the  nature  and  properties  of 
bodies,  be  attained  by  the  microscope  1  la 
it  possible  to  make  the  gluten  in  a  piece  of 
bread  visible  in  all  its  connections  and  rami- 
fications ?  It  is  impossible  by  means  of  in- 
struments ;  but  if  the  piece  of  bread  is  placed 
in  a  lukewarm  decoction  of  malt,  the  starch , 
and  the  substance  called  dextrine,*  are  seen 
to  dissolve  like  sugar  in  water,  and,  at  last, 
nothing  remains  except  the  gluten,  in  the 


*  According  to  Raspail,  starch  consists  of  vesi- 
cles inclosing  within  them  a  fluid  resembling  gum. 
Starch  may  be  put  in  cold  water  without  being 
dissolved  :  but,  when  placed  in  hot  water,  these 
spherules  burst,  and  allow  the  escape  of  the  liquid. 
This  liquid  is  the  dextrine  of  Biot,  so  called  be- 
cause it  possesses  the  property  of  turning  the 
plane  of  the  polarization  of  light  to  the  right  hand. 
—ED. 


ASSIMILATION    OF    CARBON. 


21 


form  of  a  spongy  mass,  the  minute  pores  of 
which  can  be  seen  only  by  a  microscope. 

Chemistry  offers  innumerable  resources 
of  this  kind  which  are  of  the  greatest  use  in 
an  inquiry  into  the  nature  of  the  organs  of 
plants;  but  they  are  not  used,  because  the 
need  of  them  is  not  felt.  The  most  import- 
ant organs  of  animals  and  their  functions 
are  known,  although  they  may  not  be  visi- 
ble to  the  naked  eye.  But  in  vegetable  phy- 
sioijgy,  a  leaf  is  in  every  case  regarded 
merely  as  a  leaf,  notwithstanding  that  leaves 
generating  oil  of  turpentine  or  oil  of  lemons 
must  possess  a  different  nature  from  those 
in  which  oxalic  acid  is  formed.  Vitality,  in 
its  peculiar  operations,  makes  use  of  a  spe- 
cial apparatus  for  each  function  of  an  organ. 
A  rose  twig  engrafted  upon  a  lemon  tree 
does  not  bring  forth  lemons,  but  roses. 
Vegetable  physiologists  in  the  study  of  their 
science  have  not  directed  their  attention  to 
that  part  of  it  which  is  most  worthy  of  in- 
vestigation. 

The  second  cause  of  the  incredulity  with 
which  physiologists  view  the  theory  of  the 
nutrition  of  plants  by  the  carbonic  acid  of 
the  atmosphere  as,  that  the  art  of  experi- 
menting is  not  known  in  physiology,  it  being 
an  art  which  can  be  learned  accurately  only 
»n  the  chemical  laboratory.  Nature  speaks 
"ft  us  in  a  peculiar  language,  in  the  language 
of  phenomena;  she  answers  at  all  times  the 
questions  which  are  put  to  her;  and  such 
questions  are  experiments.  An  experiment 
is  the  expression  of  a  thought :  we  are  near 
the  truth  when  the  phenomena  elicited  by 
the  experiment  corresponds  to  the  thought; 
while  the  opposite  result  shows  that  the 
question  was  falsely  stated,  and  that  the 
conception  was  erroneous. 

The  critical  repetition  of  another's  experi- 
ments must  be  viewed  as  a  criticism  of  his 
opinions ;  if  the  result  of  the  criticism  be 
merely  negative,  if  it  do  not  suggest  more 
correct  ideas  in  the  place  of  those  which  it 
is  intended  to  refute,  it  should  be  disre- 
garded ;  because  the  worse  experimenter  the 
critic  is,  the  greater  will  be  the  discrepancy 
between  the  results  he  obtains  and  the  views 
proposed  by  the  other. 

It  is  too  much  forgotten  by  physiologists, 
that  their  duty  really  is  not  to  refute  the  ex- 
periments of  others,  nor  to  show  that  they 
are  erroneous,  but  to  discover  truth,  and 
that  alone.  It  is  startling,  when  we  reflect 
that  all  the  time  and  energy  of  a  multitude 
of  persons  of  genius,  talent,  and  knowledge, 
are  expended  in  endeavours  to  demonstrate 
each  other's  errors. 

The  question  whether  carbonic  acid  is  the 
food  of  plants  or  not  has  been  made  the  sub- 
ject of  experiments  with  perfect  zeal  and 
good  faith ;  the  results  have  been  opposed 
to  that  view.  But  how  was  tne  inquiry  in- 
stituted'? 

The  seeds  of  balsamines,  beans,  cresses, 
and  gourds,  were  sown  in  pure  Carrara 
marble,  and  sprinkled  with  water  containing 
carbonic  acid.  The  seeds  sprang,  but  the 


plants  did  not  attain  to  the  development  of 
the  third  small  leaf.  In  other  cases,  they 
allowed  the  water  to  penetrate  the  marble 
from  below,  yet,  in  spite  of  this,  they  died. 
It  is  worthy  of  observation,  that  they  lived 
longer  with  pure  distilled  water  than  with 
that  impregnated  with  carbonic  acid;  but 
still,  in  this  case  also,  they  eventually  pe- 
rished. Other  experimenters  sowed  seeds 
of  plants  in  flowers  of  sulphur  and  sulphate 
of  barytes,  and  tried  to  nourish  them  with 
carbonic  acid,  but  without  success. 

Such  experiments  have  been  considered 
as  positive  proofs,  that  carbonic  acid  will 
not  nourish  plants ;  but  the  manner  in  which 
they  were  instituted  is  opposed  to  all  rules 
of  philosophical  inquiry,  and  to  all  the  laws 
of  chemistry. 

Many  conditions  are  necessary  for  the 
life  of  plants  ;  those  of  each  genus  require 
special  conditions ;  and  should  but  one  of 
these  be  wanting,  although  the  rest  be  sup- 
plied, the  plants  will  not  be  brought  to  ma- 
turity. The  organs  of  a  plant,  as  well  as 
those  of  an  animal,  contain  substances  of 
the  most  different  kinds;  some  are  formed 
solely  of  carbon  and  the  elements  of  water, 
others  contain  nitrogen,  and  in  all  plants  we 
find  metallic  oxides  in  the  state  of  salts. 
The  food  which  can  serve  for  the  produc- 
tion of  all  the  organs  of  a  plant,  must  neces- 
sarily contain  all  its  elements.  These  most 
essential  of  all  the  chemical  qualities  of  nu- 
triment may  be  united  in  one  substance,  or 
they  may  exist  separately  in  several ;  in 
which  case,  the  one  contains  what  is  want- 
ing in  the  other.  Dogs  die  although  fed 
with  jelly,  a  substance  which  contains  ni- 
trogen ;  they  cannot  live  upon  white  bread, 
sugar  or  starch,  if  these  are  given  as  food, 
to  the  exclusion  of  all  other  substances. 
Can  it  be  concluded  from  this,  that  these 
substances  contain  no  elements  suited  for 
assimilation?  Certainly  not. 

Vitality  is  the  power  which  each  organ 
possesses  of  constantly  reproducing  itself ; 
for  this  it  requires  a  supply  of  substance  a 
which  contain  the  constituent  elements 
of  its  own  substance,  and  are  capable 
of  undergoing  transformation.  All  the 
organs  together  cannot  generate  a  single 
element,  carbon,  nitrogen,  or  a  metallic 
oxide. 

When  the  quantity  of  the  food  is  too 
great,  or  is  not  capable  of  undergoing  the 
necessary  transformation,  or  exerts  any  pe- 
culiar cnemical  action,  the  organ  itself  is 
subjected  to  a  change  :  all  poisons  act  in  this 
manner.  The  most  nutritious  substances 
may  cause  death.  In  experiments  such  as 
those  described  above,  every  condition  of 
nutrition  should  be  considered.  Besides 
those  matters  whi"h  form  their  principal 
constituent  parts,  both  animals  and  plants 
require  others,  the  peculiar  functions  ot 
which  are  unknown.  These  are  inorganic 
substances,  such  as  common  salt,  the  total 
want  of  which  is  in  animals  inevitably  pro- 
ductive of  death.  Plants,  for  me  same  rea- 


AGRICULTURAL   CHEMIS'iRY. 


son,  cannot  live  unless  supplied  with  cer- 
tain metallic  compounds. 

If  we  knew  with  certainty  that  there  ex- 
isted a  substance  capable  alone  of  nour- 
ishing a  plant  and  of  bringing  it  to  maturity, 
we  might  be  led  to  a  knowledge  of  the  con- 
ditions necessary  to  the  life  of  all  plants,  by 
studying  its  characters  and  composition.  If 
humus  were  such  a  substance,  it  would 
have  precisely  the  same  value  as  the  only 
single  food  which  nature  has  produced  for 
animal  organization,  namely,  milk  (Prout.) 
The  constituents  of  milk  are  cheese  or 
caseine,  a  compound  containing  nitrogen  in 
large  proportion ;  butter,  in  which  hydrogen 
abounds  j  and  sugar  of  milk,  a  substance 
with  a  large  quantity  of  hydrogen  and  oxy- 
gen in  the  same  proportion  as  in  water.  It 
also  contains  in  solution,  lactate  of  soda, 
phosphate  of  lime,  and  common  salt;  and  a 
peculiar  aromatic  product  exists  in  the  but- 
ter, called  butyric  acid.  The  knowledge  of 
the  composition  of  milk  is  a  key  to  the  con- 
ditions necessary  for  the  purposes  of  nutri- 
tion of  all  animals. 

All  substances  which  are  adequate  to  the 
nourishment  of  animals  contain  those  ma- 
terials united,  though  not  always  in  the 
same  form ;  nor  can  any  one  be  wanting  for 
a  certain  space  of  time,  without  a  marked 
effect  on  the  health  being  produced.  The 
employment  of  a  substance  as  food  presup- 
poses a  knowledge  of  its  capacity  of  assimi- 
lation, and  of  the  conditions  under  which 
this  takes  place. 

A  carnivorous  animal  dies  in  the  vacuum 
of  an  air  pump,  even  though  supplied  with 
a  superabundance  of  food  j  it  dies  in  the  air, 
if  the  demands  of  its  stomach  are  not  satis- 
fied ;  and  it  dies  in  pure  oxygen  gas,  how- 
ever lavishly  nourishment  be  given  to  it.  Is 
it  hence  to  be  concluded,  that  neither  flesh, 
nor  air,  nor  oxygen,  is  fitted  to  support  life? 
Certainly  not. 

Prom  the  pedestal  of  the  Trajan  column 
at  Rome  we  might  chisel  out  each  single 
piece  of  stone,  if  upon  the  extraction  of  the 
second  we  replaced  the  first.  But  could  we 
conclude  from  this  that  the  column  was  sus- 
pended in  the  air,  and  not  supported  by  a 
single  piece  of  its  foundation  ?  Assuredly 
not.  Yet  the  strongest  proof  would  have 
been  given  that  each  portion  of  the  pedestal 
could  be  removed,  without  the  downfall  of 
the  column. 

Animal  and  vegetable  physiologists,,  how- 
ever, come  to  such  conclusions  with  re- 
spect to  the  process  of  assimilation.  They 
institute  experiments,  without  being  ac- 
quainted with  the  circumstances  necessary 
for  the  continuance  of  life — with  the  quali- 
ties and  proper  nutriment  of  the  animal  or 
plant  on  which  they  operate — or  with  the 
nature  and  chemical  constitution  of  its 
organs.  These  experiments  are  considered 
by  them  as  convincing  proofs,  while  they 
are  fitted  only  to  awaken  pity. 

Is  it  possible  to  bring  a  plant  to  maturity  i 
by  means  of  carbonic  acid  and  water,  with-  I 


out  the  aid  of  some  substance  con tuuimg  ni- 
trogen, which  is  an  essential  constituent  oi 
the  sap,  and  indispensable  for  its  produc- 
tion ?  Must  the  plant  not  die,  however 
abundant  the  supply  of  carbonic  acid  may 
be,  as  soon  as  the  first  small  leaves  have 
exhausted  the  nitrogen  contained  in  the 
seeds  1 

Can  a  plant  be  expected  to  grow  in  Car- 
rara marble,  even  when  an  azotised  sub- 
stance is  supplied  to  it,  if  the  marble  be 
sprinkled  with  an  aqueous  solution  of  car- 
bonic acid,  which  dissolves  the  lime  and 
forms  bicarbonate  of  lime  ?  A  plant  of  the 
family  of  the  Plumbaginece,  upon  the  leaves 
of  which  fine  hornlike,  or  scaly  processes 
of  crystallised  carbonate  of  lime  are  formed, 
might,  perhaps,  attain  maturity  under  such 
circumstances;  but  these  experiments  are 
only  sufficient  to  prove,  that  cresses,  gourds, 
and  baisamines,  cannot  be  nourished  by 
bicarbonate  of  lime,  in  the  absence  of  mat- 
ter containing  nitrogen.  We  may,  indeed, 
conclude,  that  the  salt  of  lime  acts  as  a 
poison,  since  the  developement  of  plants 
will  advance  farther  in  pure  water,  when 
lime  and  carbonic  acid  are  not  used. 

Moist  flowers  of  sulphur  attract  oxygen 
from  the  atmosphere,  and  become  acid.  Is 
it  possible  that  a  plant  can  grow  and  flourish 
in  presence  of  free  sulphuric  acid,  with  no 
other  nourishment  than  carbonic  acid  ?  It  is 
true,  the  quantity  of  sulphuric  acid  formed 
thus  in  hours,  or  in  days,  may  be  small,  but 
the  property  of  each  particle  of  the  sulphur 
to  absorb  oxygen  and  retain  it,  is  present 
every  moment. 

When  it  is  known  that  piants  require 
moisture,  carbonic  acid,  and  air,  should  we 
choose  as  the  soil  for  experiments  on  their 
growth,  sulphate  of  barytes,  which,  from  its 
nature  and  specific  gravity,  completely  pre- 
vents the  access  of  air? 

All  these  experiments  are  valueless  for  the 
decision  of  any  question.  It  is  absurd  to 
take  for  them  any  soil,  at  mere  hazard,  as 
long  as  we  are  ignorant  of  the  functions 
performed  in  plants  by  those  inorganic  sub- 
stances which  are  apparently  foreign  to 
them.  It  is  quite  impossible  to  mature  a 
plant  of  the  family  of  the  Graminece,  or  of 
the  Equisctacece,  the  solid  framework  of 
which  contains  silicate  of  potash,  without 
silicic  acid  and  potash,  or  a  plant  of  the  ge- 
nus Oxalis  without  potash,  or  saline  plants 
such  as  the  saltworts  (Salsola  and  Salicorma) 
without  chloride  of  sodium,  or  at  least  some 
salt  of  similar  properties.  All  seeds  of  the 
Graminece  contain  phosphate  of  magnesia ; 
the  solid  parts  of  the  roots  of  the  althcea  con- 
tain more  phosphate  of  lime  than  woody  fibre. 
Are  these  substances  merely  accidentally 
present  ?  A  plant  should  not  be  chosen  for 
experiment,  when  the  matter  which  it  re 
quires  for  its  assimilation  is  not  well  known, 

What  value,  now,  can  be  attached  to  ex- 
periments in  which  all  those  matters  which 
a  plant  requires  in  the  process  of  assimila- 
tion, besides  its  mere  nutriment,  1  ave  been 


ORIGIN   AND   ACTION   OF  HUMUS. 


excluded  with  the  greatest  care  ?  Can  the 
laws  of  life  be  investigated  in  an  organised 
being  which  is  diseased  or  dying? 

The  mere  observation  of  a  wood  or  mea- 
dow is  infinitely  better  adapted  to  decide  so 
simple  a  question  than  all  the  trivial  experi- 
ments under  a  glass  globe ;  the  only  dif- 
ference is  that  instead  of  one  plant  there  are 
thousands.  When  we  are  acquainted  with 
the  nature  of  a  single  cubic  inch  of  their 
scil,  and  know  the  composition  of  the  air 
and  rainwater,  we  are  in  possession  of  all 
the  conditions  necessary  to  their  life.  The 
source  of  the  different  elements  entering  into 
the  composition  of  plants  cannot  possibly 
escape  us,  if  we  know  in  what  form  they 
take  up  their  nourishment,  and  compare  its 
composition  with  that  of  the  vegetable  sub- 
stances which  compose  their  structure. 

All  these  questions  will  now  be  examined 
and  discussed.  It  has  been  already  shown 
that  the  carbon  of  plants  is  derived  from  the 
atmosphere :  it  still  remains  for  us  to  in- 
quire what  power  is  exerted  on  vegetation 
by  the  numus  of  the  soil  and  the  inorganic 
constituents  of  plants  and  also  to  trace  the 
sources  of  their  nitrogen. 


CHAPTER  III. 


ON   THE    ORIGIN   AND   ACTION   OF    HUMUS. 

IT  will  be  shown  in  the  second  part  of 
this  work,  that  all  plants  and  vegetable 
structures  undergo  two  processes  of  decom- 
position after  death.  One  of  these  is  named 
fermentation;  the  other,  putrefaction,  decay, 
or  eremacausis* 

It  will  likewise  be  shown,  that  decay  is  a 
slow  process  of  combustion, — a  process, 
therefore,  in  which  the  combustible  parts  of 
a  plant  unite  with  the  oxygen  of  the  atmo- 
sphere. 

The  decay  of  woody  fibre  (the  principal 
constituent  of  all  plants)  is  accompanied  by 
a  phenomenon  of  a  peculiar  kind.  This 
substance,  in  contact  with  air  or  oxygen 
gas,  converts  the  latter  into  an  equal  volume 
of  carbonic  acid,  and  its  decay  ceases  upon 
the  disappearance  of  the  oxygen.  If  the 
carbonic  acid  is  removed,  and  oxygen  re- 
placed, its  decay  recommences,  that  is,  it 
again  converts  oxygen  into  carbonic  acid. 
Woody  fibre  consists  of  carbon  and  the  ele- 
ments of  water  ;  and  if  we  judge  only  from 
the  products  formed  during  its  decomposi- 
tion, and  from  those  formed  by  pure  char- 
coal, burned  at  a  high  temperature,  we 
might  conclude  that  the  causes  were  the 
same  in  both :  the  decay  of  woody  fibre  pro- 
ceeds, therefore,  as  if  no  hydrogen  or  oxy- 
gen entered  into  its  composition. 


A  very  long  time  is  required  for  the  com- 
pletion of  this  process  of  combustion,  and  the 
presence  of  water  is  necessary  for  its  main- 
tenance :  alkalies  promote  it,  but  acids  re- 
tard it;  all  antiseptic  substances,  such  as 
sulphurous  acid,  the  mercurial  salts,  empy- 
reumatic  oils,  &c.,  cause  its  complete  ces 
sation. 

Woody  fibre  in  a  state  of  decay  is  U.e 
substance  called  humus* 

The  property  of  woody  fibre  t?  ^  nvert 
surrounding  oxygen  gas  into  carbotuc  acid 
diminishes  in  proportion  as  its  decay  ad- 
vances, and  at  last  a  certain  quantity  of  a 
brown  coaly-looking  substance  remains,  in 
which  this  property  is  entirely  wanting 
This  substance  is  called  mould;  it  is  the 
product  of  the  complete  decay  of  woody 
fibre.  Mould  constitutes  the  principal  of  aL 
the  strata  of  brown  coal  and  peat. 

Humus  acts  in  the  same  manner  in  a  soil 
permeable  to  air  as  in  the  air  itself;  it  is  a 
continued  source  of  carbonic  acid,  which  it 
emits  very  slowly.  An  atmosphere  of  car- 
bonic acid,  formed  at  the  expense  of  the  air, 
surrounds  every  particle  of  decaying  humus. 
The  cultivation  of  land,  by  tilling  and  loos- 
ening the  soil,  causes  a  free  and  unob- 
structed access  of  air.  An  atmosphere  of 
carbonic  acid  is,  therefore,  contained  in  every 
fertile  soil,  and  is  the  first  and  most  import- 
ant food  for  the  young  plants  which  grow 
in  it. 

In  spring,  when  those  organs  of  plants 
are  absent  which  nature  has  appointed  for 
the  assumption  of  nourishment  from  the 
atmosphere,  the  component  substance  of  the 
seeds  is  exclusively  employed  in  the  forma- 
tion of  the  roots.  Each  new  radicle  fibril 
which  a  plant  acquires  may  be  regarded  as 
constituting  at  the  same  time  a  mouth,  a 
lung,  and  a  stomach.  The  roots  perform 
the  functions  of  the  leaves  from  the  first 
moment  of  their  formation  :  they  extract 
from  the  soil  their  proper  nutriment,  namely, 
the  carbonic  acid  generated  by  the  humus. 

By  loosening  the  soil  which  surrounds 
young  plants,  we  favour  the  access  of  air, 
and  the  formation  of  carbonic  acid;  and,  on 
the  other  hand,  the  quantity  of  their  food 
is  diminished  by  every  difficulty  which  op- 
poses the  renewal  of  air.  A  plant  itself 
effects  this  change  of  air  at  a  certain  period 
of  its  growth.  The  carbonic  acid,  which 
protects  the  undecayed  humus  from  farther 
change,  is  absorbed  and  taken  away  by  tbur 
fine  fibres  of  the  roots,  and  by  the  root? 
themselves  ;  this  is  replaced  by  atmospheric 
air,  by  which  process  the  decay  is  renewed, 
and  a  fresh  portion  of  carbonic  acid  formed. 
A  plant  at  this  time  receives  its  food  both 
by  the  roots  and  by  theorgans  aboveground, 
and  advances  rapidly  to  maturity. 

When  a  plant  is  quite  matured,  and  when 


. J 

*  The  word  eremacausis  was  proposed  by  the 
author  some  time  since,  in  order  to  explain  the 

true   nature  of  decay;   it   is    compounded   from    decomposition  of  humus  by  alkalies  ;  it  does  not 
degrees  and  **vriitburning.  '  exist  in  the  humus  of  vegetable  physiologists. 


The  humic  acid  of  chemists  is  a  product  of  the 


AGRICULTURAL    CHEMISTRY. 


the  organs  by  which  it  obtains  food  from 
the  atmosphere  are  formed,  the  carbonic  acid 
of  the  soil  is  no  farther  required. 

Deficiency  of  moisture  in  the  soil,  or  its 
complete  dryness,  does  not  now  check  the 
growth  of  a  plant,  provided  it  receives  from 
the  dew  and  the  atmosphere  as  much  as  is 
requisite  for  the  process  of  assimilation. 
During  the  heat  of  summer  it  derives  its 
carbon  exclusively  from  the  atmosphere. 

We  do  not  know  what  height  and  strength 
nature  has  allotted  to  plants;  we  are  ac- 
quainted only  with  the  size  which  they 
usually  attain.  Oaks  are  shown,  both  in 
London  and  Amsterdam,  as  remarkable 
curiosities,  which  have  been  reared  by  Chi- 
nese gardeners,  and  are  only  one  foot  and  a 
half  in  height,  although  their  trunks,  barks, 
leaves,  branches,  and  whole  habitus,  evince 
a  venerable  age.  The  small  parsnep  grown 
at  Teltow,*  when  placed  in  a  soil  which 
yields  as  much  nourishment  as  it  can  take 
up,  increases  to  several  pounds  in  weight. 

The  size  of  a  plant  is  proportional  to  the 
surface  of  the  organs  which  are  destined  to 
convey  food  to  it.  A  plant  gains  another 
mouth  and  stomach  with  every  new  fibre 
of  root,  and  every  new  leaf. 

The  power  which  roots  possess  of  taking 
up  nourishment  does  not  cease  as  long  as 
nutriment  is  present.  When  the  food  of  a 
plant  is  in  greater  quantity  than  its  organs 
r  -quire  for  their  own  perfect  development, 
tiit  superfluous  nutriment  is  not  returned  to 
the  soil,  but  is  employed  in  the  formation  of 
new  organs.  At  the  side  of  a  cell,  already 
formed,  another  cell  arises ;  at  the  side  of  a 
twig  and  leaf,  a  new  twig  and  a  new  leaf 
are  developed.  These  new  parts  could  not 
have  been  formed  had  there  not  been  an 
excess  of  nourishment.  The  sugar  and 
mucilage  produced  in  the  seeds,  form  the 
nutriment  of  the  young  plants,  and  disap- 
pear during  the  development  of  the  buds, 
green  sprouts,  and  leaves. 

The  power  of  absorbing  nutriment  from 
the  atmosphere,  with  which  the  leaves  of 
plants  are  endowed,  being  proportionate  to 
the  extent  of  their  surface,  every  increase 
in  the  size  and  number  of  these  parts  is  ne- 
cessarily attended  with  an  increase  of  nutri- 
tive power,  and  a  consequent  farther  de- 
velopment of  new  leaves  and  branches. 
Leaves,  twigs,  and  branches,  when  com- 
pletely matured,  as  they  do  not  become 
larger,  do  not  need  food  for  their  support. 
For  their  existence  as  organs,  they  require 
only  the  means  necessary  for  the  perform- 
ance of  the  special  functions  to  which  they 
are  destined  by  nature;  they  do  not  exist  on 
their  own  account. 

We  know  that  the  functions  of  the  leaves 
and  other  green  parts  of  plants  are  to  absorb 
carbonic  acid,  and  with  the  aid  of  light  and 


*  Teltow  is  a  village  near  Berlin,  where  small 
parsneps  are  cultivated  in  a  sandy  soil ;  they  are 
nuch  esteemed,  and  weigh  rarely  above  one 
t  unce. 


moisture,  to  appropriate  its  carbon.  These 
processes  are  continually  in  operation  ;  they 
commence  with  the  first  formation  of  the 
leaves,  and  do  not  cease  with  their  perfect 
development.  But  the  new  products  arising 
from  this  continued  assimilation  are  no 
longer  employed  by  the  perfect  leaves  in 
their  own  increase :  they  serve  for  the  for- 
mation of  woody  fibre,  and  all  the  solid 
matters  of  similar  composition.  The  leaves 
now  produce  sugar,  amylin  or  starch,  and 
acids,  which  were  previously  formed  by  the 
roots  when  they  were  necessary  for  the  de^ 
velopment  of  the  stem,  buds,  leaves,  and 
branches  of  the  plant. 

The  organs  of  assimilation,  at  this  period 
of  their  life,  receive  more  nourishment  from 
the  atmosphere  than  they  employ  in  their 
own  sustenance ;  and  when  the  formation 
of  the  woody  substance  has  advanced  to  a 
certain  extent,  the  expenditure  of  the  nutri- 
ment, the  supply  of  which  still  remains  the 
same,  takes  a  new  direction,  and  blossoms 
are  produced.  The  functions  of  the  leaves 
of  most  plants  cease  upon  the  ripening  of 
their  fruit,  because  the  products  of  their 
action  are  no  longer  needed.  They  now 
yield  to  the  chemical  influence  of  the  oxygen 
of  the  air,  generally  suffer  a  change  in 
colour,  and  fall  off. 

A  peculiar  "transformation"  of  the  mat- 
ters contained  in  all  plants  takes  place  in  the 
period  between  blossoming  and  the  ripening 
of  the  fruit;  new  compounds  are  produced, 
which  furnish  constituents  of  the  blossoms, 
fruit,  and  seed.  An  organic  chemical 
"transformation"  is  the  separation  of  the 
elements  of  one  or  several  combinations, 
and  their  re-union  into  two  or  several  others, 
which  contain  the  same  number  of  elements, 
either  grouped  in  another  manner,  or  in  dif- 
ferent proportions.  Of  two  compounds 
formed  in  consequence  of  such  a  change, 
one  remains  as  a  component  part  of  the 
blossom  or  fruit,  while  the  other  is  separated 
by  the  roots  in  the  form  of  excrementitious 
matter.  No  process  of  nutrition  can  be  con- 
ceived to  subsist  in  aniraals  or  vegetables, 
without  a  separation  of  effete  matters.  We 
know,  indeed,  that  an  organized  body  can- 
not generate  substances,  but  can  only  change 
the  mode  of  their  combination,  and  that  its 
sustenance  and  reproduction  depend  upon 
the  chemical  transformation  of  the  matters 
which  are  employed  as  its  nutriment,  and 
which  contain  its  own  constituent  elements. 

Whatever  we  regard  as  the  cause  of  these 
transformations,  whether  the  Vital  Principle, 
Increase  of  Temperature,  Light,  Galvanism, 
or  any  other  influence,  the  act  of  transfor- 
mation is  a  purely  chemical  process.  Com- 
bination and  Decomposition  can  take  place 
only  when  the  elements  are  disposed  to 
these  changes.  That  which  chemists  name 
affinity  indicates  only  the  degree  in  which 
they  possess  this  disposition.  It  will  be 
shown,  when  considering  the  processes  of 
fermentation  and  putrefaction,  that  every 
disturbance  of  the  mutual  attraction  sub- 


ORGANIC    SUBSTANCES. 


misting  between  the  elements  of  a  body  gives 
rise  to  a  transformation.  The  elements  ar- 
range themselves  according  to  the  degrees 
of  their  reciprocal  attraction  into  new  com- 
binations, which  are  incapable  of  farther 
change  under  the  same  conditions. 

The  products  of  these  transformations 
vary  with  their  causes,  that  is,  with  the  dif- 
ferent conditions  on  which  their  production 
depended ;  and  are  as  innumerable  as  these 
conditions  themselves.  The  chemical  cha- 
racter of  an  acid,  for  example,  is  its  un- 
ceasing disposition  to  saturation  by  means 
of  a  base  ;  this  disposition  differs  in  intensity 
i»  different  acids ;  but  when  it  is  satisfied, 
the  acid  character  entirely  disappears.  The 
chemical  character  of  a  base  is  exactly  the 
reverse  of  this,  but  both  an  acid  and  a  base, 
notwithstanding  the  great  difference  in  their 
properties,  effect,  in  most  cases,  the  same 
kinl  of  transformations. 

Hvdrocyanic  acid  and  water  contain  the 
elements  of  carbonic  acid,  ammonia,  urea, 
cyanuric  acid,  cyanilic  acid,  oxalic  acid,  for- 
mic acid,  melam,  ammelin,  melamin,  azulmin, 
mdlon,  hydromellonic  acid,  allantoin,  fyc.  It 
is  well  known,  that  all  these  very  different 
substances  can  be  obtained  from  hydrocyanic 
acid  and  the  elements  of  water,  by  various 
chemical  transformations. 

The  whole  process  of  nutrition  may  be 
understood  by  the  consideration  of  one  of 
these  transformations. 

Hydrocyanic  acid  and  water,  for  example, 
when  brought  into  contact  with  muriatic 
acid,  are  decomposed  into  formic  acid  and 
ammonia  ;  both  of  these  products  of  decom- 
position contain  the  elements  of  hydrocyanic 
acid  and  water,  although  in  another  form, 
and  arranged  in  a  different  order.  The 
change  results  from  the  strong  disposition 
or  struggle  of  muriatic  acid  to  undergo  satu- 
ration, in  consequence  of  which  the  hydro- 
cyanic acid  and  water  suffer  mutual  decom- 
position. The  nitrogen  of  the  hydrocyanic 
acid  and  the  hydrogen  of  the  water  unite 
together  and  form  a  base,  ammonia,  with 
which  the  acid  unites ;  the  chemical  charac- 
ters of  the  acid  being  at  the  same  time  lost, 
because  its  desire  for  saturation  is  satisfied 
by  its  uniting  with  ammonia.  Ammonia 
itself  was  not  previously  present,  but  only 
its  elements,  and  the  power  to  form  it.  The 
simultaneous  decomposition  of  hydrocyanic 
acid  and  water  in  this  instance  does  not  take 
place  in  consequence  of  the  chemical  affinity 
of  muriatic  acid  for  ammonia,  since  hydro- 
cyanic acid  and  water  contain  no  ammonia. 
An  affinity  of  one  body  for  a  second  which 
is  totally  without  the  sphere  of  its  attrac- 
tions, or  which,  so  far  as  it  is  concerned, 
does  not  exist,  is  quite  inconceivable.  The 
ammonia  in  this  case  is  formed  only  on  ac- 
count of  the  existing  attractive  desire  of  the 
acid  for  saturation.  Hence  we  may  perceive 
how  much  these  modes  of  decomposition,  to 
which  the  name  of  transformations  or  meta- 
morphoses has  been  especially  applied,  differ 
from  the  ordinary  chemical  (iecompositions. 
4 


In  consequence  of  the  formation  of  am- 
monia, the  other  elements  of  hydrocyanic 
acid,  namely,  carbon  and  hydrogen,  unite 
with  the  oxygen  of  the  decomposed  water, 
and  form  formic  acid,  the  elements  of  this 
substance  with  the  power  of  combination 
being  present.  Formic  acid  here  represents 
the  excremenlitious  matters  ;  ammonia,  the 
new  substance,  assimilated  by  an  organ  of  a 
plant  or  animal. 

Each  organ  extracts  from  the  food  pre- 
sented to  it  what  it  requires  for  its  own  sus- 
tenance; while  the  remaining  elements, 
which  are  not  assimilated,  combine  together 
and  are  separated  as  excrement.  The  ex- 
crementitious  matters  of  one  organ  come  in 
contact  with  another  during  their  passage 
through  the  organism,  and  in  consequence 
suffer  new  transformations ;  the  useless  mat- 
ters rejected  by  one  organ  containing  the 
elements  for  the  nutrition  of  a  second  and  a 
third  organ  :  but  at  last,  being  capable  of  no 
farther  transformations,  they  are  separated 
from  the  system  by  the  organs  destined  for 
that  purpose.  Each  part  of  an  organized 
being  is  fitted  for  its  peculiar  functions.  A 
cubic  inch  of  sulphuretted  hydrogen  intro- 
duced into  the  lungs  would  cause  instant 
death,  but  it  is  formed,  under  a  variety  of 
circumstances,  in  the  intestinal  canal  with- 
out any  injurious  effect. 

In  consequence  of  such  transformations 
as  we  have  described,  excrements  are  formed 
of  various  composition,  some  of  these  con- 
tain carbon  in  excess,  others  nitrogen,  and 
others  again  hydrogen  and  oxygen.  The 
kidneys,  liver,  and  lungs,  are  organs  of  ex- 
cretion ;  the  first  separate  from  the  body  all 
those  substances  in  which  a  large  propor- 
tion of  nitrogen  is  contained;  the  second, 
those  with  an  excess  of  carbon ;  and  the 
third,  such  as  are  composed  principally  of 
oxygen  and  hydrogen.  Alcohol,  also,  and 
the  volatile  oils  which  are  incapable  of  be- 
ing assimilated,  are  exhaled  through  the 
lungs,  and  not  through  the  skin. 

Respiration  must  be  regarded  as  a  slow 
process  of  combustion  or  constant  decompo- 
sition. If  it  be  subject  to  the  laws  which 
regulate  the  processes  of  decomposition  gene- 
rally, the  oxygen  of  the  inspired  air  cannot 
combine  directly  with  the  carbon  of  com- 
pounds of  that  element  contained  in  the 
blood;  the  hydrogen  only  can  combine  with 
the  oxygen  of  the  air,  or  undergo  a  higher 
degree  of  oxidation.  Oxygen  is  absorbed 
without  uniting  with  carbon ;  and  carbonic 
acid  is  disengaged,  the  carbon  and  oxygen 
of  which  must  be  derived  from  matters  pre- 
viously existing  in  the  blood.* 


*  The  examination  of  the  air  expired  by  con- 
sumptive persons,  as  well  as  of  their  blood,  would 
doubtless  throw  much  light  on  the  nature  of  phthisis 
pulmonaris.  Considered  in  a  chemical  point  of 
view,  the  decomposition  of  the  blood,  as  it  takes 
place  in  the  lungs,  is  a  true  process  of  putrefac- 
tion. (See  Part  II.)  The  lungs  are  also  the  seat 
of  the  transformation  of  the  various  substances 
contained  in  the  blood.  It  certainly  well  merit* 


26 


AGRICULTURAL    CHEMISTRY. 


All  superabundant  nitrogen  is  eliminated 
from  the  body,  as  a  liquid  excrement, 
through  the  urinary  passages ;  all  solid  sub- 
stances, incapable  of  farther  transformation, 
pass  out  by  the  intestinal  canal,  and  all 
gaseous  matter  by  the  lungs. 

We  should  not  permit  ourselves  to  be 
withheld  by  the  idea  of  a  vital  principle, 
from  considering  in  a  chemical  point  of  view 
the  process  of  the  transformation  of  the  food, 
and  its  assimilation  by  the  various  organs. 
This  is  the  more  necessary,  as  the  views, 
hitherto  held,  have  produced  no  results,  and 
are  quite  incapable  of  useful  application. 

Is  it  truly  vitality,  which  generates  sugar 
m  the  germ  for  the  nutrition  of  young  plants, 
or  which  gives  to  the  stomach  the  power  to 
dissolve,  and  to  prepare  for  assimilation,  all 
the  matter  introduced  into  it  ?  A  decoction 
of  malt  possesses  as  little  power  to  repro- 
duce itself,  as  the  stomach  of  a  dead  calf; 
both  are,  unquestionably,  destitute  of  life. 
But  when  amylin  or  starch  is  introduced 
into  a  decoction  of  malt,  it  changes,  first 
into  a  gummy-like  matter,  and  lastly  into 
sugar.  Hard-boiled  albumen  and  muscular 
fibre  can  be  dissolved  in  a  decoction  of  a 
calf's  stomach,  to  which  a  few  drops  of  mu- 
riatic acid  have  been  added,  precisely  as  in 
the  stomach  itself.*  (Schwann,  Schulz.) 

The  power,  therefore,  to  effect  transfor- 
mations, does  not  belong  to  the  vital  prin- 
ciple :  each  transformation  is  owing  to  a 
disturbance  in  the  attraction  of  the  elements 
of  a  compound,  and  is  consequently  a 
purelv  chemical  piocess.  There  is  no  doubt 
that  this  process  takes  place  in  another  form 
from  that  of  the  ordinary  decomposition  of 
salts,  oxides,  or  sulphurets.  But  is  it  the 
fault  of  chemistry  that  physiology  has  hith- 
erto taken  no  notice  of  this  new  form  of 
chemical  action  ? 

Physicians  are  accustomed  to  administer 
whole  ounces  of  borax  to  patients  suffering 
under  urinary  calculi,  when  it  is  known 
that  the  bases  of  all  alkaline  salts  formed  by 
organic  acids  are  carried  through  the  urinary 
passages  in  the  form  of  alkaline  carbonates, 
capable*  of  dissolving  calculi  (Wohler.)  Is 
this  rational'?  The  medical  reports  state, 
that  upon  the  Rhine,  where  so  much  cream 
of  tartar  is  consumed  in  wine,  the  only  cases 
of  calculous  disorders  are  those  which  are 
imported  from  other  districts.  We  know 
that  the  uric  acid  calculus  is  transformed 

consideration,  that  the  most  approved  remedies 
for  counteracting  or  stopping  the  progress  of  this 
frightful  malady  are  precisely  those  which  are 
found  most  efficacious  in  retarding  putrefaction. 
Thus,  it  is  well  known  that  much  relief  is  afforded 
by  a  residence  in  works  in  which  empyreumatic 
oils  are  manufactured  by  dry  distillation,  such  as 
manufactories  for  the  preparation  of  gas  or  sal-am- 
moniac. For  the  same  reason,  the  respiration  of 
wood  vinegar  (pyroligneous  acid,)  of  chlorine,  and 
certain  of  the  acids,  has  been  recognized  as  a 
means  of  alleviating  the  disease. 

*  This  remarkable  action  has  been  completely 
confirmed  in  this  laboratory  (Giessen,)  by  Dr. 
Vogel,  a  highly  distinguished  young  physiologist. 


into  the  mulberry  calculus  (which  contains 
oxalic  acid,)  when  patients  suffering  undei 
the  former  exchange  the  town  for  the  coun- 
try, where  less  animal  and  more  vegetable 
food  is  used.  Are  all  these  circumstances 
incapable  of  explanation? 

The  volatile  oil  of  the  roots  of  valerian 
may  be  obtained  from  the  oil  generated  dur- 
ing the  fermentation  of  potatoes  (Dumas,) 
and  the  oil  of  the  Spircea  ulmaria  from  the 
crystalline  matter  of  the  bark  of  the  willow 
(Piria.)  We  are  able  to  form  in  our  labor- 
atories formic  acid,  oxalic  acid,  urea,  and 
the  crystalline  substances  existing  in  the 
liquid  of  the  allantois  of  the  cow,  all  pro- 
ducts, it  is  said,  of  the  vital  principle.  We 
see,  therefore,  that  this  mysterious  principle 
has  many  relations  in  common  with  chemi- 
cal forces,  and  that  the  latter  can  indeed  re- 
place it.  What  these  relations  are,  it 
remains  for  physiologists  to  investigate. 
Truly  it  would  be  extraordinary  if  this  vital 
principle,  which  uses  every  thing  for  its  own 
purposes,  had  alloted  no  share  to  chemical 
forces,  which  stand  so  freely  at  its  disposal. 
We  shall  obtain  that  which  is  obtainable  in 
a  rational  inquiry  into  nature,  if  we  se- 
parate the  actions  belonging  to  chemical 
powers  from  those  which  are  subordinate  to 
other  influences.  But  the  expression  "  vital 
principle"  must  in  the  mean  time  be  consi- 
dered as  of  equal  value  with  the  terms  spe- 
cific or  dynamic  in  medicine :  every  thing  is 
specific  which  we  cannot  explain,  and 
dynamic  is  the  explanation  of  all  which  we 
do  not  understand  j  the  terms  having  been 
invented  merely  for  the  purpose  of  conceal- 
ing ignorance  by  the  application  of  learned 
epithets. 

Transformations  of  existing  compounds 
are  constantly  taking  place  during  the  whole 
life  of  a  plant,  in  consequence  of  which, 
and  as  the  results  of  these  transformations, 
there  are  produced  gaseous  matters  which 
are  excreted  by  the  leaves  and  blossoms,  solid 
excrements  deposited  in  the  bark,  and  fluid 
soluble  substances  which  are  eliminated  by 
the  roots.  Such  secretions  are  most  abun- 
dant immediately  before  the  formation  and 
during  the  continuance  of  the  blossoms; 
they  diminish  after  the  development  of  the 
fruit.  Substances  containing  a  large  propor- 
tion of  carbon  are  excreted  by  the  roots  and 
absorbed  by  the  soil.  Through  the  expul- 
sion of  these  matters  unfitted  for  nutrition, 
the  soil  receives  again  with  usury,  the  car- 
bon which  it  had  at  first  yielded  to  the 
young  plants  as  food,  in  the  form  of  car- 
bonic acid. 

The  soluble  matter  thus  acquired  by  the 
soil  is  still  capable  of  decay  and  putrefaction, 
and  by  undergoing  these  processes  furnishes 
renewed  sources  of  nutrition  to  another  gene- 
ration of  plants;  it  becomes  humus.  The  culti- 
vated soil  is  thus  placed  in  a  situation  exactly 
analogous  to  that  of  forests  and  meadows, 
for  the  leaves  of  trees  which  fall  in  the  forest 
in  autumn,  and  the  old  roots  of  grass  in  the 
meadow,  are  likewise  converted  into  humus 


ORGANIC   CHEMICAL   PROCESSES. 


27 


by  the  same  influence  :  a  soil  receives  mor. 
carbon  in  this  form  than  its  decaying  humus 
had  lost  as  carbonic  acid. 

Plants  do  not  exhaust  the  carbon  of  a  soi 
in  the  normal  condition  of  their  growth;  on 
the  contrary,  they  add  to  its  quantity.  Bu 
if  it  is  true  that  plants  give  back  more  car- 
bon to  a  soil  than  they  take  from  it,  it  is  evi- 
dent that  their  growth  must  depend  upon  the 
reception  of  nourishment  from  the  atmo- 
sphere in  the  form  of  carbonic  acid.  The 
influence  of  humus  upon  vegetation  is  ex- 
plained by  the  foregoing  facts  in  the  most 
clear  and  satisfactory  manner. 

Humus  does  not  nourish  plants  by  bein 
taken  up  and  assimilated  in   its   unaltere 
state,  but  by  presenting  a  slow  and  lasting 
source  of  carbonic  acid,  which  is  absorbed 
by  the  roots,  and  is  the  principal  nutriment 
of  young  plants  at  a  time  when,  being  des- 
titute of  leaves,  they  are  unable  to  extract 
food  from  the  atmosphere. 

In  former  periods  of  the  earth's  history, 
its  surface  was  covered  with  plants,  the  re- 
mains of  which  are  still  found  in  the  coal 
formations.  These  plants — the  gigantic 
monocotyledons,  ferns,  palms,  and  reeds — 
Velong  to  a  class  to  which  nature  has  given 
tne  power,  by  means  of  an  immense  exten- 
sion of  their  leaves,  to  dispense  with  nour- 
ishment from  the  soil.  They  resemble  in 
this  respect  the  plants  which  we  raise  from 
bulbs  and  tubers,  and  which  live  while 
young  upon  the  substances  contained  in 
their  seed,  and  require  no  food  from  the  soil 
when  their  exterior  organs  of  nutrition  are 
formed.  This  class  of  plants  is  even  at 
present  ranked  amongst  those  which  do  not 
exhaust  the  soil. 

The  necessity  of  the  existence  of  plants 
such  as  these  at  the  commencement  of  ve- 
getation, must  now  be  apparent.  Humus 
is  a  product  of  the  decay  of  vegetable  mat- 
ter, and  therefore  could  not  have  existed 
to  supply  the  first  plants  with  the  food  neces- 
sary for  the  development  of  the  more  deli- 
cate kinds.  Hence  the  plants  capable  of 
flourishing  under  such  circumstances  could 
only  be  those  which  receive  their  nourish- 
ment from  tne  air  alone.  By  their  decay, 
however,  the  soil  in  which  they  grew  be- 
came supplied  with  vegetable  matter,  and 
the  progress  of  vegetation  must  have  fur- 
nished to  the  earth  materials  adapted  for  the 
development  of  those  plants,  which  depend 
upon  the  nutriment  contained  in  the  soil, 
until  those  organs  are  formed  which  are  des- 
tined for  the  assumption  of  nourishment 
from  the  atmosphere. 

The  plants  of  every  former  period  are  dis- 
tinguished from  those  of  the  present  by  the 
inconsiderable  development  of  their  roots. 
Fruit,  leaves,  seeds,  nearly  every  part  of  the 
plants  of  a  former  world,  except  the  roots, 
are  found  in  the  brown  coal  formation.  The 
vascular  bundles,  and  the  perishable  cellular 
tissue,  of  which  their  roots  consisted,  have 
been  the  first  to  suffer  decomposition.  But 
when  we  examine  oaks  and  other  trees, 


which  in  consequence  of  revolutions  of  the 
same  kind  occurring  in  later  ages  have  un- 
dergone the  same  changes,  we  never  find 
their  roots  absent. 

The  verdant  plants  of  warm  climates  are 
very  often  such  as  obtain  from  the  soil  only 
a  point  of  attachment,  and  are  not  dependent 
on  it  for  their  growth.  How  extreme!? 
small  are  the  roots  of  the  Cactus,  Sedum> 
and  Sempervivum,  in  proportion  to  their 
mass,  and  to  the  surface  of  their  leaves! 
Large  forests  are  often  found  growing  in 
soils  absolutely  destitute  of  carbonaceous 
matter;  and  the  extensive  prairies  of  the 
western  continent  show  that  the  carbon 
necessary  for  the  sustenance  of  a  plant  may 
be  entirely  extracted  from  the  atmosphere. 
Again,  in  the  most  dry  and  barren  sand, 
where  it  is  impossible  for  nourishment  to  be 
obtained  through  the  roots,  we  see  the  milky- 
juiced  plants  attain  complete  perfection. 
The  moisture  necessary  for  the  nutrition  of 
these  plants  is  derived  from  the  atmosphere, 
and  when  assimilated  is  secured  from  eva- 
poration by  the  nature  of  the  juice  itself. 
Caoutchouc  and  wax,  which  are  formed  in 
these  plants,  surround  the  water,  as  in  oily 
emulsions,  with  an  impenetrable  envelope 
by  which  the  fluid  is  retained,  in  the  same 
manner  as  milk  is  prevented  from  evaporat- 
ing by  the  skin  which  forms  upon  it. 
These  plants,  therefore,  become  turgid  with 
their  juices. 

Particular  examples  might  be  cited  of 
plants,  which  have  been  brought  to  maturity, 
upon  a  small  scale,  without  the  assistance 
of  mould ;  but  fresh  proofs  of  the  accuracy 
of  our  theory  respecting  the  origin  of  carbon 
would  be  superfluous  and  useless,  and 
could  not  render  more  striking,  or  more  con- 
vincing, the  arguments  already  adduced.  It 
must  not,  however,  be  left  unmentioned, 
that  common  wood  charcoal,  by  virtue 
merely  of  its  ordinary  well-known  proper- 
ties, can  completely  replace  vegetable  mould 
or  humus.  The  experiments  of  Lukas, 
which  are  appended  to  this  work,  spare  me 
all  further  remarks  upon  its  efficacy. 

Plants  thrive  in  powdered  charcoal,  and 
may  be  brought  to  blossom  and  bear  fruit  if 
exposed  to  the  influence  of  the  rain  and  the 
atmosphere;  the  charcoal  may  be  previously 
heated  to  redness.  Charcoal  is  the  most 
indifferent"  and  most  unchangeable  sub- 
stance known  ;  it  may  be  kept  for  centuries 
without  change,  and  is,  therefore,  not  sub- 
ject to  decomposition.  The  only  substances 
which  it  can  yield  to  plants  are  some  salts, 
which  it  contains,  amongst  which  is  silicate 
of  potash.  It  is  known,  however,  to  pos- 
sess the  power  of  condensing  gases  within 
its  pores,  and  particularly  carbonic  acid. 
And  it  is  by  virtue  of  this  power  that  the 
roots  of  plants  are  supplied  in  charcoal,  ex- 
actly as  in  humus,  with  an  atmosphere  of 
carbonic  acid  and  air,  which  is  renewed  as 
quickly  as  it  is  abstracted. 

In  charcoal  powder,  which  had  been  used 
for  this  purpose  by  Lukas  for  several  years. 


AGRICULTURAL    CHEMISTRY. 


Buchner  found  a  brown  substance  soluble 
in  alkalies.  This  substance  was  evidently 
due  to  the  secretions  from  the  roots  of  the 
plants  which  grew  in  it. 

A  plant  placed  in  a  closed  vessel  in  which 
the  air,  and  therefore  the  carbonic  acid,  can- 
not be  renewed,  dies  exactly  as  it  would  do 
in  the  vacuum  of  an  air-pump,  or  in  an  at- 
mosphere of  nitrogen  or  carbonic  acid,  even 
though  its  roots  be  fixed  in  the  richest  mould. 

Plants  do  not,  however,  attain  maturity, 
under  ordinary  circumstances,  in  charcoal 
powder,  when  they  are  moistened  with  pure 
distilled  water  instead  of  rain  or  river  water. 
Rain  water  must,  therefore,  contain  within 
it  one  of  the  essentials  of  vegetable  life ;  and 
it  will  be  shown,  that  this  is  the  presence  of 
a  compound  containing  nitrogen,  the  exclu- 
sion of  which  entirely  deprives  humus  and 
charcoal  of  their  influence  upon  vegetation. 


CHAPTER  IV. 

ON   THE    ASSIMILATION    OF    HYDROGEN. 

THE  atmosphere  contains  the  principal 
food  of  plants  in  the  form  of  carbonic  acid, 
in  the  state,  therefore,  of  an  oxide.  The 
solid  part  of  plants  (woody  fibre)  contains 
carbon  and  the  constituents  of  water,  or  the 
elements  of  carbonic  acid,  together  with  a 
certain  quantity  of  hydrogen.  It  has  for- 
merly been  mentioned  that  water  consists  of 
the  two  gases,  oxygen  and  hydrogen.  The 
range  of  affinity  possessed  by  both  these 
elements  is  so  extensive  that  numerous 
causes  occur  which  effect  the  decomposition 
of  water.  Indeed,  there  is  no  compound 
which  plays  a  more  general  or  more  im- 
portant part  in  the  phenomena  of  combina- 
tion and  decomposition.  We  can  conceive 
the  wood  to  arise  from  a  combination  of  the 
carbon  of  the  carbonic  acid  with  the  elements 
of  water,  under  the  influence  of  solar  light. 
In  this  case,  72.35  parts  of  oxygen,  by  weight, 
must  be  separated  as  a  gas  for  every  27.65 
parts  of  carbon,  which  are  assimilated  by  a 
plant;  for  this  is  the  composition  of  carbonic 
acid  in  100  parts.  Or,  what  is  much  more 
probable,  plants,  under  the  same  circum- 
stances, may  decompose  water,  the  hydro- 
gen of  which  is  assimilated  along  with'  car- 
bonic acid,  whilst  its  oxygen  is  separated. 
If  the  latter  change  takes  place,  8.04  parts 
of  hydrogen  must  unite  with  100  parts  of 
carbonic  acid,  in  order  to  form  woody  fibre, 
and  the  72.35  parts  by  weight  of  oxygen, 
which  was  in  combination  with  the  hydro- 
gen of  the  water,  and  which  exactly  corre- 
sponds in  quantity  with  the  oxygen  contained 
in  the  carbonic  acid,  must  be  separated  in  a 
gaseous  form. 

Each  acre  of  land,  which  produces  10 
cwts.  of  carbon,  gives  annually  to  the  at- 
mosphere 865  Ibs.  of  free  oxygen  gas.  The 
specific  weight  of  oxygen  is  expressed  by 
the  number  1.1026;  hence  1  cubic  metre  of 


oxygen  weighs  3.157  Ibs.,  and  2865  Ibs.  of 
oxygen  correspond  to  908  cubic  metres,  or 
32,007  cubic  feet. 

An  acre  of  meadow,  wood,  or  cultivated 
land  in  general  replaces,  therefore,  in  the 
atmosphere  as  much  oxygen  as  is  exhausted 
by  10  cwts.  of  carbon,  either  m  its  ordinary 
combustion  in  the  air  or  in  the  respiratory 
process  of  animals. 

It  has  been  mentioned  at  a  former  page 
that  pure  woody  fibre  contains  carbon  and 
the  component  parts  of  water,  but  that  ordi- 
nary wood  contains  more  hydrogen  than 
corresponds  to  this  proportion.  This  excess 
is  owing  to  the  presence  of  the  green  princi- 
ple of  the  leaf,  wax.,  resin,  and  other  bodies 
rich  in  hydrogen.  Water  must  be  decom- 
posed, in  order  to  furnish  the  excess  of  this 
element,  and  consequently  one  equivalent  of 
oxygen  must  be  given  back  to  the  atmosphere 
for  every  equivalent  of  hydrogen  appropri- 
ated by  a  plant  to  the  production  of  those  sub- 
stances. The  quantity  of  oxygen  thus  set  at 
liberty  cannot  be  insignificant,  for  the  at- 
mosphere must  receive  989  cubic  feet  of 
oxygen  for  every  pound  of  hydrogen  assi- 
milated. 

It  has  already  been  stated,  that  a  plant,  in 
the  formation  of  woody  fibre,  must  always 
yield  to 'the  atmosphere  the  same  propor- 
tional quantity  of  oxygen ;  that  the  volume 
of  this  gas  set  free  would  be  the  same 
whether  it  were  due  to  the  decomposition  of 
carbonic  acid  or  of  water.  A  little  consi- 
deration will  show  that  this  must  be  the  case. 
It  has  repeatedly  been  stated,  that  woody 
fibre  contains  carbon  in  combination  with 
oxygen  and  hydrogen  in  the  same  propor- 
tion in  which  they  exist  in  water.  Water 
contains  1  equivalent  of  each  element,  whilst 
carbonic  acid  consists  of  1  equivalent  of 
carbon,  united  to  2  equivalents  of  oxygen. 
In  the  formation  of  woody  fibre,  2  equiva- 
lents of  oxygen  must  therefore  be  libe- 
rated. The  woody  fibre  can  only  be 
formed  in  one  of  two  ways  :  either  the  car- 
bon of  carbonic  acid  unites  directlv  with 
water,  or  the  hydrogen  of  water  combines 
with  the  oxygen  of  the  carbonic  acid.  In 
the  former  of  these  cases,  the  two  equiva- 
lents of  oxygen  in  the  carbonic  acid  must  be 
liberated ;  in  the  latter,  two  atoms  of  wate~ 
must  be  decomposed,  the  hydrogen  of  which 
unites  with  the  oxygen  of  the  carbonic  acid, 
whilst  the  oxygen  of  the  water,  thus  set 
free,  is  disengaged  in  the  state  of  a  gas.  It 
was  considered  most  probable  that  the  latter 
was  the  case. 

From  their  generating  caoutchouc,  wax, 
fats,  and  volatile  oils  containing  nydrogen 
in  large  quantity,  and  no  oxygen,  we  may 
be  certain  that  plants  possess  the  rjroperty 
of  decomposing  water,  because  from  no 
other  body  could  they-obtain  the  hydrogen 
of  those  matters.  It  has  also  been  proved 
by  the  observations  of  Humboldt  on  the 
fungi,  that  water  may  be  decomposed  with- 
out the  assimilation  of  hydrogen.  Water  13 
a  remarkable  combination  of  two  elements. 


ASSIMILATION   OF  HYDROGEN. 


which  have  the  power  to  separate  them- 
selves from  one  another,  in  innumerable 
processes,  in  a  manner  imperceptible  to  our 
senses  ;  while  carbonic  acid,  on  the  contrary, 
is  only  decomposable  by  violent  chemical 
action. 

Most  vegetable  structures  contain  hydro- 
gen in  the  form  of  water,  which  can  be  sepa- 
rated as  such,  and  replaced  by  other  bodies ; 
but  the  hydrogen  which  is  essential  to  their 
constitution  caunot  possibly  exist  in  the  state 
of  water. 

All  the  hydrogen  necessary  for  the  forma- 
tion of  an  organic  compound  is  supplied  to 
a  plant  by  the  decomposition  of  water.  The 
process  of  assimilation,  in  its  most  simple 
form,  consists  in  the  extraction  of  hydrogen 
from  water,  and  carbon  from  carbonic  acid, 
in  consequence  of  which,  either  all  the  oxy- 
gen of  the  water  and  carbonic  acid  is  sepa- 
rated, as  in  the  formation  of  caoutchouc,  the 
volatile  oils  which  contain  no  oxygen,  and 
other  similar  substances,  or  only  a  part  of  it 
is  exhaled. 

The  known  composition  of  the  organic 
compounds  most  generally  present  in  vege- 
tables, enables  us  to  state  in  definite  propor- 
tions the  quantity  of  oxygen  separated  during 
their  formation. 

36  eq.  carbonic  acid  and") 

22  eq.  hydrogen  derived  >=  Woody  Fibra, 
from  22  eq.  water.          J 

with  the  separation  of  72  eq.  oxygen. 
36  eq.  carbonic  acid  and") 

S6  eq.  hydrogen  derived  >=  Sugar, 
from  36  eq.  water 

with  the  separation  of  72  eq.  oxygen. 
36  eq.  carbonic  acid  and") 

30  eq.  hydrogen  derived  >=  Starch, 
from  30  eq.  water  J 

with  the  separation  of  72  eq.  oxygen. 
36  eq.  carbonic  acid  and^ 

16  eq.  hydrogen  derived  >=  Tannic  Acid, 
from  16  eq.  water          3 

with  the  separation  of  64  eq.  oxygen. 
36  eq.  carbonic  acid  and") 

18  eq.  hydrogen  derived  >=  Tartaric  Acid, 
from  18  eq.  water  J 

with  the  separation  of  45  eq.  oxygen. 
36  eq.  carbonic  acid  and") 

18  eq.  hydrogen  derived  >=  Malic  Acid, 
from  18  eq.  water          3 

with  the  separation  of  54  eq.  oxygen. 
36  eq.  carbonic  acid  and} 
24  eq.  hydrogen  derived  >  =  Oil  of  Turpentine. 
from  24  eq.  water  ) 

with  the  separation  of  84  eq.  oxygen. 

It  will  readily  be  perceived  that  the  for- 
mation of  the  acids  is  accompanied  with  the 
smallest  separation  of  oxygen ;  that  the 
amount  of  oxygen  set  free  increases  with  the 
production  of  the  so-named  neutral  sub- 
stances, and  reaches  its  maximum  in  the 
formation  of  the  oils.  Fruits  remain  acid 
in  cold  summers ;  while  the  most  numerous 
trees  under  the  tropics  are  those  which  pro- 
duce oils,  caoutchouc,  fcnd  other  substances 
containing  very  little  oxygen.  The  action 
of  sunshine  and  influence  of  heat  upon  the 
ripening  of  fruit  is  thus,  in  a  certain  mea- 
sure, represented  by  the  numbers  above 
cited 


The  green  resinous  principle  of  the  leaf 
diminishes  in  quantity,  while  oxygen  is  ah* 
sorbed,  when  fruits  are  ripened  in  the  dark ; 
red  and  yellow  colouring  matters  are  formed  ; 
tartaric,  citric,  and  tannic  acids  disappear, 
and  are  replaced  by  sugar,  amylin,  or  gum. 
6  eq.  Tartaric  Acid,  by  absorbing  6  eq. 
oxygen  from  the  air,  form  Grape  Sugar, 
with  the  separation  of  12  eq.  carbonic  acid. 
1  eq.  Tannic  Acid,  by  absorbing  8  eq.  oxy- 
gen from  the  air,  and  4  eq.  water,  form  1 
eq.  of  Amylin,  or  starch,  with  separation  of 
6  eq.  carbonic  acid. 

We  can  explain,  in  a  similar  manner,  tne 
formation  of  all  the  component  substances 
of  plants  which  contain  no  nitrogen,  whether 
they  are  produced  from  carbonic  acid  and 
water,  with  separation  of  oxygen,  or  by  the 
conversion  of  one  substance  into  the  other, 
by  the  assimilation  of  oxygen  and  separation 
of  carbonic  acid.  We  do  not  know  in  what 
form  the  production  of  these  constituents 
takes  place ;  in  this  respect,  the  representa- 
tion of  their  formation  which  we  have  given 
must  not  be  received  in  an  absolute  sense, 
it  being  intended  only  to  render  the  nature 
of  the  process  more  capable  of  apprehension ; 
but  it  must  not  be  forgotten,  that  if  the  con- 
version of  tartaric  acid  into  sugar,  in  grapes, 
be  considered  as  a  fact,  it  must  take  place 
under  all  circumstances  in  the  same  propor- 
tions. 

The  vital  process  in  plants  is,  with  refer- 
ence to  the  point  we  have  been  considering, 
the  very  reverse  of  the  chemical  processes 
engaged  in  the  formation  of  salts.  Carbonic 
acid,  zinc,  and  water,  when  brought  into 
contact,  act  upon  one  another,  and  hydrogen 
is  separated,  while  a  white  pulverulent 
compound  is  formed,  which  contains  car- 
bonic acid,  zinc,  and  the  oxygen  of  the 
water.  A  living  plant  represents  the  zinc 
in  this  process  :  but  the  process  of  assimila- 
tion gives  rise  to  compounds,  which  contain 
the  elements  of  carbonic  acid  and  the  hydro- 
gen of  water,  whilst  oxygen  is  separated. 

Decay  has  been  described  above  as  the 
great  operation  of  nature,  by  which  that 
oxygen,  which  was  assimilated  by  plants 
during  life,  is  again  returned  to  the  atmo- 
sphere. During  the  progress  of  growth, 
plants  appropriate  carbon  in  the  form  of  car- 
bonic acid,  and  hydrogen  from  the  decom- 
position of  water,  the  oxygen  of  which  is 
set  free,  together  with  a  part  of  all  that  con- 
tained in  the  carbonic  acid.  In  the  process 
of  putrefaction,  a  quantity  of  water,  exactly 
corresponding  to  that  of  tb.e  hydrogen,  is 
again  formed  by  extraction  of  oxygen  from 
the  air;  while  all  the  oxygen  of  the  organic 
matter  is  returned  to  the  atmosphere  in  the 
form  of  carbonic  acid.  Vegetable  matters 
can  emit  carbonic  acid,  during  their  decay, 
only  in  proportion  to  the  quantity  of  oxygen 
which  they  contain;  acids,  therefore,  yield 
more  carbonic  acid  than  neutral  compounds  ; 
while  fatty  acids,  resin,  and  wax,  do  not 
putrefy ;  they  remain  in  the  soil  without  any 
apparent  change. 

B2 


so 


AGRICULTURAL    CHEMISTRY. 


The  numerous  springs  which  emit  car- 
bonic acid  in  the  neighbourhood  of  extinct 
volcanoes,  must  be  regarded  as  another 
means  of  compensating  for  the  carbonic  acid 
absorbed  and  retained  by  plants  during  life, 
and  consequently  as  a  source  by  which  oxy- 
gen is  supplied  to  the  atmosphere.  Bischof 
calculated  that  the  springs  of  carbonic  acid 
in  the  Eifel  (a  volcanic  district  near  Cob- 
lenz)  send  into  the  air  every  day  more  than 
1 10,000  Ibs.  of  carbonic  acid,  corresponding 
to  79,000  Ibs.  of  pure  oxygen. 


.  CHAPTER  V. 

ON   THE    ORIGIN   AND   ASSIMILATION    OF 
NITROGEN. 

WE  cannot  suppose  that  a  plant  could 
attain  maturity,  even  in  the  richest  vege- 
table mould,  without  the  presence  of  matter 
containing  nitrogen;  since  we  know  that 
nitrogen  exists  in  every  part  of  the  vegetable 
structure.  The  first  and  most  important 
question  to  be  solved,  therefore,  is:  How 
and  in  what  form  does  nature  furnish  nitro- 
gen to  vegetable  albumen,  and  gluten,  to 
fruits  and  seeds? 

This  question  is  susceptible  of  a  very 
simple  solution. 

Plants,  as  we  know,  grow  perfectly  well 
in  pure  charcoal,  if  supplied  at  the  same 
time  with  rain  water.  Rain  water  can  con- 
tain nitrogen  only  in  two  forms,  either  as 
dissolved  atmospheric  air,  or  as  ammonia, 
which  consists  of  this  element  and  hydro- 
gen. Now,  the  nitrogen  of  the  air  cannot 
be  made  to  enter  into  combination  with  any 
element  except  oxygen,  even  by  the  employ- 
ment of  the  most  powerful  chemical  means. 
We  have  not  the  slightest  reason  for  believ- 
ing that  the  nitrogen  of  the  atmosphere 
takes  part  in  the  processes  of  assimilation 
of  plants  and  animals;  on  the  contrary,  we 
know  that  many  plants  emit  the  nitrogen 
which  is  absorbed  by  their  roots,  either  in 
the  gaseous  form,  or  in  solution  in  water. 
But  there  are  on  the  other  hand  numerous 
facts,  showing,  that  the  formation  in  plants 
of  substances  containing  nitrogen,  such  as 
gluten,  takes  place  in  proportion  to  the 
quantity  of  this  element  which  is  conveyed 
to  their  roots  in  the  state  of  ammonia,  de- 
rived from  the  putrefaction  of  animal  matter. 

Ammonia,  too,  is  capable  of  undergoing 
such  a  multitude  of  transformations,  when 
in  contact  with  other  bodies,  that  in  this 
respect  it  is  not  inferior  to  water,  which  pos- 
sesses the  same  property  in  an  eminent  de- 
gree. It  possesses  properties  which  we  do 
not  find  in  any  other  compound  of  nitrogen  : 
when  pure,  it  is  extremely  soluble  in  water; 
it  forms  soluble  compounds  with  all  the 
acids;  and  when  in  contact  with  certain 
other  substances,  it  completely  resigns  its 
characters  an  a.kali,  and  is  capable  of  as- 


suming the  most  various  and  opposite  forms 
Formate  of  ammonia  changes,  under  the 
influence  of  a  high  temperature,  into  hy- 
drocyanic acid  and  water,  without  the  sepa- 
ration of  any  of  its  elements.  Ammonia  forms 
urea,  with  cyanic  acid,  and  a  series  of  crys- 
talline compounds,  with  the  \olatile  oils  of 
mustard  and  bitter  almonds.  It  changes 
into  splendid  blue  or  red  colouring  matters, 
when  in  contact  with  the  bitter  constituent 
of  the  bark  of  the  apple-tree  (phloridzin,) 
with  the  sweet  principle  of  the  F^ariolaiia 
dealbata  (orcm,)  or  with  the  tasteless  matter 
of  the  Rocella  tinctoria  (en///inn.)  All  blue 
colouring  matters  which  are  reddened  by 
acids,  and  all  red  colouring  substances 
which  are  rendered  blue  by  alkalies,  contain 
nitrogen,  but  not  in  the  form  of  a  base. 

These  facts  are  not  sufficient  to  establish 
the  opinion  that  it  is  ammonia  which  affords 
all  vegetables,  without  exception,  the  nitro- 
gen which  enters  into  the  composition  of 
their  constituent  substances.  Considerations 
of  another  kind,  however,  give  to  this  opi- 
nion a  degree  of  certainty  which  completely 
excludes  all  other  views  of  the  matter. 

Let  us  picture  to  ourselves  the  condition 
of  a  well-cultured  farm,  so  large  as  to  be  in- 
dependent of  assistance  from  other  quarters. 
On  this  extent  of  land  there  is  a  certain 
quantity  of  nitrogen  contained  both  in  the 
corn  and  fruit  which  it  produces,  and  in  the 
men  and  animals  which  feed  upon  them, 
and  also  in  their  excrements.  We  shall 
suppose  this  quantity  to  be  known.  The 
land  is  cultivated  without  the  importation 
of  any  foreign  substance  containing  nitro- 
gen. Now,  the  products  of  this  farm  'must 
be  exchanged  every  year  for  money,  and 
other  necessaries  of  life — for  bodies,  there- 
fore, which  contain  no  nitrogen.  A  certain 
proportion  of  nitrogen  is  exported  with  corn 
and  cattle ;  and  this  exportation  lakes  place 
every  year,  without  the  smallest  compensa- 
tion ;  yet  after  a  given  number  of  years,  the 
quantity  of  nitrogen  will  be  found  to  have 
increased.  Whence,  we  may  ask,  comes 
this  increase  of  nitrogen?  The  nitrogen  in 
the  excrements  cannot  reproduce  itself,  and 
the  earth  cannot  yield  it.  Plants,  and  con- 
sequently animals,  must,  therefore,  derive 
their  nitrogen  from  the  atmosphere. 

It  will  in  a  subsequent  part  of  this  work 
be  shown  that  the  last  products  of  the  decay 
and  putrefaction  of  animal  bodies  present 
themselves  in  two  different  forms.  They 
are  in  the  form  of  a  combination  of  hydro- 
gen and  nitrogen — ammonia — in  the  temper- 
ate and  cold  climates,  and  in  that  of  a  com- 
pound containing  oxygen — nitric  acid — in 
the  tropics  and  hot  climates.  The  forma- 
tion of  the  latter  is  preceded  by  the  produc- 
tion of  the  first.  Ammonia  is  the  last  pro- 
duct of  the  putrefaction  of  animal  bodies; 
nitric  acid  is  the  product  of  the  transforma- 
tion of  ammonia.  A  generation  of  a  thou- 
sand million  men  is  renewed  every  thirty 
years :  thousands  of  millions  of  animafs 
cease  to  live  and  are  reproduced,  in  a  much 


ASSIMILATION   OF   NITROGEN. 


31 


snorter  period.  Where  is  the  nitrogen 
which  they  contained  during  life?  There  is 
no  question  which  can  be  answered  with 
more  positive  certainty.  All  animal  bodies 
during  their  decay  yield  the  nitrogen  which 
they  contain  to  the  atmosphere,  in  the  form 
of  ammonia.  Even  in  the  bodies  buried  sixty 
feet  under  ground  in  the  churchyard  of  the 
Eglise  des  Innocens,  at  Paris,  all  the  nitro- 
gen contained  in  the  adipocire  was  in  the 
state  of  ammonia.  Ammonia  is  the  simplest 
of  all  the  compounds  of  nitrogen ;  and  hy- 
drogen is  the  element  for  which  nitrogen 
possesses  the  most  powerful  affinity. 

The  nitrogen  of  putrified  animals  is  con- 
tained in  the  atmosphere  as  ammonia,  in  the 
form  of  a  gas  which  is  capable  of  entering 
into  combination  with  carbonic  acid  and  of 
forming  a  volatile  salt.  Ammonia  in  its 
gaseous  form,  as  well  as  all  its  volatile  com- 
pounds, is  of  extreme  solubility  in  water. 
Ammonia,  therefore,  cannot  remain  long  in 
the  atmosphere,  as  every  shower  of  rain 
must  condense  it,  and  convey  it  to  the  sur- 
face of  the  earth.  Hence,  also,  rain-water 
must  at  all  times  contain  ammonia,  though 
not  always  in  equal  quantity.  It  must  be 
greater  in  summer  than  in  spring  or  in  win- 
ter, because  the  intervals  of  time  between 
the  showers  are  in  summer  greater;  and 
when  several  wet  days  occur,  the  rain  of 
the  first  must  contain  more  of  it  than  that 
of  the  second.  The  rain  of  a  thunder  storm, 
after  a  long-protracted  drought,  ought  for 
this  reason  to  contain  the  greatest  quantity 
which  is  conveyed  to  the  earth  at  one  time. 

But  we  have  formerly  stated,  that  all  the 
analyses  of  atmospheric  air  hitherto  made 
have  failed  to  demonstrate  the  presence  of 
ammonia,  although,  according  to  our  view, 
it  can  never  be  absent.  Is  it  possible  that  it 
could  have  escaped  our  most  delicate  and 
most  exact  apparatus  ?  The  quantity  of  ni- 
trogen contained  in  a  cubic  foot  or  air  is 
certainly  extremely  small,  but,  notwithstand- 
ing this,  the  sum  of  the  quantities  of  nitro- 
gen from  thousands  and  millions  of  dead 
animals  is  more  than  sufficient  to  supply  all 
those  living  at  one  time  with  this  element. 

From  the  tension  of  aqueous  vapour  at 
150  c.  (59°  F.)=6,98  lines  (Paris  mea- 
sure,) and  from  its  known  specific  gravity 
at  0°  C.  (32°  F.,)  it  follows  that  when  the 
temperature  of  the  air  is  59°  F.  and  the 
height  of  the  barometer  28",  1  cubic  metre 
or  35.3  cubic  feet  of  aqueous  vapour  are 
contained  in  487  cubic  metres,  or  17,191 
cubic  feet  of  air:  35.3  cubic  feet  of  aqueous 
vapour  weigh  about  1^  Ib.  Consequently, 
if  we  suppose  that  the  air  saturated  with 
moisture  at  59°  F.  allows  all  the  water 
which  it  contains  in  the  gaseous  form  to  fall 
as  rain,  then  1.1  pound  of  rain-water  must 
be  obtained  from  every  11,471  cubic  feet  of 
air.  The  whole  quantity  of  ammonia  con- 
tained in  the  same  number  of  cubic  feet  will 
also  be  returned  to  the  earth  in  this  one 
pound  of  rain-water.  But  if  the  11,471 
cubic  feet  of  air  contain  a  single  grain  of 


ammonia,  then  ten  cubic  inches — the  quan- 
tity usually  employed  in  an  analysis — must 
contain  only  0.000000048  of  a  grain.  This 
extremely  small  proportion  is  absolutely  in- 
appreciable by  the  most  delicate  and  best 
eudiometer;  it  might  be  classed  among  the 
errors  of  observation,  even  were  its  quan- 
tity ten  thousand  times  greater.  But  the 
detection  of  ammonia  must  be  much  more 
easy  when  a  pound  of  rain-water  is  ex- 
amined, for  this  contains  all  the  gas  that 
was  diffused  through  1 1,471  cubic  feet  of  air. 

If  a  pound  of  rain-water  contain  only  £th 
of  a  grain  of  ammonia,  then  a  field  of  26,910 
square  feet  must  receive  annually  upwards 
of  88  Ibs.  of  ammonia,  or  71  Ibs.  of  nitro- 
gen ;  for  by  the  observations  of  Schubler, 
which  were  formerly  alluded  to,  about 
770,000  Ibs.  of  rain  fall  over  this  surface  in 
four  months,  and  consequently  the  annual 
fall  must  be  2,310,000  Ibs.  This  is  much 
more  nitrogen  than  is  contained  in  the  form 
of  vegetable  albumen  and  gluten,  in  2920 
Ibs.  of  wood,  3085  Ibs.  of  hay,  or  200  cwt. 
of  beet-root,  which  are  the  yearly  produce 
of  such  a  field ;  but  it  is  less  than  the  straw, 
roots,  and  grain  of  corn,  which  might  grow 
on  the  same  surface,  would  contain.* 

Experiments  made  in  this  laboratory 
(Giessen)  with  the  greatest  care  and  exact- 
ness have  placed  the  presence  of  ammonia 
in  rain-water  beyond  all  doubt.  It  has  ni- 
therto  escaped  observation,  because  no  per- 
son thought  of  searching  for  it.  All  the 
rain-water  employed  in  this  inquiry  was  col- 
lected 600  paces  south-west  of  Giessen, 
whilst  the  wind  was  blowing  in  the  direc- 
tion of  the  town.  When  several  hundred 
pounds  of  it  were  distilled  in  a  copper  still, 
and  the  first  two  or  three  pounds  evaporated 
with  the  addition  of  a  little  muriatic  acid,  a 
very  distinct  crystallisation  of  sal-ammoniac 
was  obtained:  the  crystals  had  always  a 
brown  or  yellow  colour. 

Ammonia  may  likewise  be  always  detected 
in  snow-water.  Crystals  of  sal-ammoniac 


*  The  advocates  of  the  importance  of  humus  af 
a  nourishment  for  plants,  being  driven  from  their 
position  by  the  facts  brought  forward  in  the  pre- 
ceding chapters,  have  found  in  the  ammonia  of  the 
atmosphere  an  explanation  of  the  manner  in  which 
humus  acquires  its  solubility,  and  therefore  its  ca- 
pability of  being  assimilated  by  plants.  Now,  it 
is  very  true  that  humic  acid  is  soluble  in  ammo 
nia ;  but  the  humic  acid  of  chemists  is  not  con 
tained  in  soils.  Were  it  so,  on  treating  moulo 
with  water  we  should  obtain  a  dark-coloured  so- 
lution of  humate  of  ammonia.  But  we  obtain  a 
solution  which  is  entirely  devoid  of  this  acid.  It 
cannot  be  too  distinctly  kept  in  mind  that  humic 
acid  is  the  product  of  the  decomposition  of  humus 
by  means  of  caustic  alkalies.  Again,  if  the 
coloured  solutions  of  humates  of  ammonia,  lime, 
or  magnesia,  be  poured  upon  good  mould  or  de- 
cayed oak-wood  (which  is  nearly  pure  humus,)  and 
allowed  to  filter,  the  solutions  are  observed  to  pass 
through  quite  colourless ;  they  are  decolourised 
just  as  if  they  had  been  filtered  through  charcoal. 
Here,  then,  humus  possesses  the  property  of  ex- 
tracting humic  acid  from  water ;  or,  in  other  words, 
soils  have  the  power  of  rendering  humic  acid  in- 
soluble, or  unfit  for  assimilation. — ED. 


32 


AGRICULTURAL  CHEMISTRY. 


were  obtained  by  evaporating  in  a  vessel 
with  muriatic  acid  several  pounds  of  snow, 
which  were  gathered  from  the  surface  of 
the  ground  in  March,  when  the  snow  had  a 
depth  of  10  inches.  Ammonia  was  set  free 
from  these  crystals  by  the  addition  of  hydrate 
of  lime.  The  inferior  layers  of  snow  which 
rested  upon  the  ground  contained  a  quantity 
decidedly  greater  than  those  which  formed 
the  surface. 

It  is  worthy  of  observation  that  the  am- 
monia contained  in  rain  and  snow  water 
possesses  an  offensive  smell  of  perspiration 
and  animal  excrements, — a  fact  which  leaves 
no  doubt  respecting  its  origin. 

Hunefield  has  proved  that  all  the  springs 
in  Greifswalde,  Wick,  Eldena,  and  Kosten- 
hagen,  contain  carbonate  and  nitrate  of  am- 
monia. Ammoniacal  salts  have  been  disco- 
vered in  many  mineral  springs  in  Kissingen 
and  other  places.  The  ammonia  of  these 
salts  can  only  arise  from  the  atmosphere. 

Any  one  may  satisfy  himself  of  the  pre- 
sence of  ammonia  in  rain  by  simply  adding 
a  little  sulphuric  or  muriatic  acid  to  a  quan- 
tity of  rain-water,  and  evaporating  this 
nearly  to  dryness  in  a  clean  porcelain  basin. 
The  ammonia  remains  in  the  residue,  in 
combination  with  the  acid  employed;  and 
may  be  detected  either  by  the  addition  of  a 
little  chloride  of  platinum,  or  more  simply 
by  a  little  powdered  lime,  which  separates 
the  ammonia,  and  thus  renders  its  peculiar 
pungent  smell  sensible.*  The  sensation 
which  is  perceived  upon  moistening  the 
hand  with  rain-water,  so  different  from  that 
produced  by  pure  distilled  water,  and  to 
which  the  term  softness  is  vulgarly  applied, 
is  also  due  to  the  carbonate  of  ammonia 
contained  in  the  former. 

The  ammonia  which  is  removed  from  the 
atmosphere  by  rain  and  other  causes,  is  as 
constantly  replaced  by  the  putrefaction  of 
animal  and  vegetable  matters.  A  certain 
portion  of  that  which  falls  with  the  rain 
evaporates  again  with  the  water,  but  another 
portion  is,  we  suppose,  taken  up  by  the 
roots  of  plants,  and  entering  into  new  com- 
binations in  the  different  organs  of  assimila- 
tion, produces  albumen,  gluten,  quinine, 
morphia,  cyanogen,  and  a  number  of  other 
compounds  containing  nitrogen.  The  chemi- 
cal characters  of  ammonia  render  it  capable 
of  entering  into  such  combinations,  and  of 
undergoing  numerous  transformations.  We 
have  now  only  to  consider  whether  it  really 


*  Since  the  appearance  of  the  last  edition,  this 
experiment  has  been  repeated  by  many  in  France, 
Germany,  America,  and  England,  and  the  exist- 
ence  of  ammonia  in  the  atmosphere  has  been 
completely  confirmed.  The  assertion  that  this 
ammonia  possesses  the  "offensive  smell  of  per- 
spiration and  animal  excrements,"  has  been  ridi- 
culed by  many  as  fanciful — 'by  none,  however, 
who  have  made  the  experiment.  The  experiment 
is  so  exceedingly  easy  to  perform,  that  any  one 
may  convince  himself  of  the  accuracy  of  the  state- 
ment.— ED. 


is  taken  up  in  the  form  of  ammonia  by  the 
roots  of  plants,  and  in  that  form  applied  by 
their  organs  to  the  production  of  the  azotisecl 
matters  contained  in  them.  This  question 
is  susceptible  of  easy  solution  by  well-known 
facts. 

In  the  year  1834, 1  was  engaged  with  Dr. 
Wilbrand,  professor  of  botany  in  the  uni- 
versity of  Giessen,  in  an  investigation  re- 
specting the  quantity  of  sugar  contained  in 
different  varieties  of  maple-trees,  which 
grew  upon  soils  which  were  not  manured. 
We  obtained  crystallised  sugars  from  all,  by 
simply  evaporating  their  juices,  without  the 
addition  of  any  foreign  substance ;  and  we 
unexpectedly  made  the  observation,  that  a 
great  quantity  of  ammonia  was  emitted  from 
this  juice  when  mixed  with  lime,  and  also 
from  the  sugar  itself  during  its  refinement. 
The  vessels  which  hung  upon  the  trees  in 
order  to  collect  the  juice  were  watched  with 
greater  attention,  on  account  of  the  sus- 
picion that  some  evil-disposed  persons  had 
introduced  urine  into  them,  but  still  a  large 
quantity  of  ammonia  was  again  found  in 
the  form  of  neutral  salts.  The  juice  had  no 
colour,  and  had  no  reaction  on  that  of  vege- 
tables. Similar  observations  were  made  upon 
the  juice  of  the  birch  tree ;  the  specimens 
subjected  to  experiment  were  taken  from  a 
wood  several  miles  distant  from  any  house, 
and  yet  the  clarified  juice,  evaporated  witlr 
lime,  emitted  a  strong  odour  of  ammonia. 

In  the  manufactories  of  beet-root  sugar, 
many  thousand  cubic  feet  of  juice  are  daily 
purified  with  lime,  in  order  to  free  it  from 
vegetable  albumen  and  gluten,  and  it  is 
afterwards  evaporated  for  crystallisation. 
Every  person  who  has  entered  such  a 
manufactory  must  have  been  astonished  at 
the  great  quantity  of  ammonia  which  is 
volatilised  along  with  the  steam.  This  am- 
monia must  be  contained  in  the  form  of  an 
ammoniacal  salt,  because  the  neutral  juice 
possesses  the  same  characters  as  the  solu- 
tion of  such-  a  salt  in  water ;  it  acquires, 
namely,  an  acid  reaction  during  evaporation, 
in  consequence  of  the  neutral  salt  being  con- 
verted by  loss  of  ammonia  into  an  acid  salt 
The  free  acid  which  is  thus  formed  is  a 
source  of  loss  to  the  manufacturers  of  sugar 
from  beet-root,  by  changing  a  part  of  thff 
sugar  into  uncrystallisable  grape  sugar  and 
syrup. 

The  products  of  the  distillation  of  flowers, 
herbs,  and  roots,  with  water,  and  all  ex- 
tracts of  plants  made  for  medicinal  purposes, 
contain  ammonia.  The  unripe,  the  trans- 
parent, and  gelatinous  pulp  of  the  almond 
and  peach  emit  much  ammonia  when  treated 
with  alkalies.  (Robiquet.)  The  juice  of  the 
fresh  tobacco  leaf  contains  ammoniaca. 
salts.  The  water  which  exudes  from  a  cm 
vine,  when  evaporated  with  a  few  drops  of 
muriatic  acid,  also  yields  a  gummy  deli- 
quescent mass,  which  evolves  much  ammo 
nia  on  the  addition  of  lime.  Ammonia  exisst 
in  every  part  of  plants,  in  the  roots  (as  ia 


ASSIMILATION    OF    NITROGEN. 


33 


beet-root,)  in  the  stem  (of  the  maple-tree,) 

and  in  all  blossoms  and  fruit  in  an  unripe 

condition. 

The  juices  of  the  maple  and  birch  contain 

both  sugar  and  ammonia,  and  therefore 
afford  all  the  conditions  necessary  for  the 
formation  of  the  azotised  components  of  the 
branches,  blossoms,  and  leaves,  as  well  as 
of  tnose  which  contain  no  azote  or  nitrogen. 
In  proportion  as  the  developement  of  those 
parts  advances,  the  ammonia  diminishes  in 
quantity,  and  when  they  are  fully  formed, 
the  tree  yields  no  more  juice. 

The  employment  of  animal  manure  in  the 
cultivation  of  grain,  and  the  vegetables 
which  serve  for  fodder  to  cattle,  is  the  most 
convincing  proof  that  the  nitrogen  of  vege- 
tables is  derived  from  ammonia.  The 
quantity  of  gluten  in  wheat,  rye,  and  bar- 
ley, is  very  different ;  these  kinds  of  grain 
also,  even  when  ripe,  contain  this  compound 
of  nitrogen  in  very  different  proportions. 
Proust  found  French  wheat  to  contain  12.5 
per  cent,  of  gluten ;  Vogel  found  that  the 
Bavarian  contained  24  per  cent.;  Davy  ob- 
tained 19  per  cent,  from  winter,  and  24  from 
summer  wheat;  from  Sicilian  21,  and  from 
Barbary  wheat  19  per  cent.  The  meal  of 
Alsace  wheat  contains,  according  to  Bous- 
singault.  17.3  per  cent,  of  gluten;  that  of 
wheat  grown  in  the  "  Jardin  des  Plantes" 
26.7,  and  that  of  winter  wheat  3.33  per  cent. 
Such  great  differences  must  be  owing  to 
some  cause,  and  this  we  find  in  the  diffe- 
rent methods  of  cultivation.  An  increase  of 
animal  manure  gives  rise  not  only  to  an  in- 
crease in  the  number  of  seeds,  but  also  to  a 
most  remarkable  difference  in  the  proportion 
of  the  substances  containing  nitrogen,  such 
as  the  gluten  which  they  contain. 

'Animal  manure,  in  as  far  as  regards  the 
assimilation  of  nitrogen,  acts  only  by  the 
formation  of  ammonia.  One  hundred  parts 
of  wheat  grown  on  a  soil  manured  with 
cow-dung  (a  manure  containing  the  smallest 
quantity  of"  nitrogen.)  afforded  only  11.95 
parts  of  gluten,  and  64.34  parts  of  amylin, 
or  starch  ;  whilst  the  same  quantity,  grown 
on  a  soil  manured  with  human  urine,  yielded 
the  maximum  of  gluten,  namely  35.1  per 
cent.  Putrefied  urine  contains  nitrogen  in 
the  forms  of  carbonate,  phosphate,  and  lac- 
tate  of  ammonia,  and  in  no  other  form  than 
that  of  ammomacal  salts. 

"  Putrid  urine  is  employed  in  Flanders  as 
a  manure  with  the  best  results.  During  the 
putrefaction  of  urine,  ammoniacal  salts  are 
formed  in  large  quantity,  it  may  be  said  ex- 
clusively; for  under  the  influence  of  heat 
and  moisture,  urea,  the  most  prominent  in- 
gredient of  the  urine,  is  converted  into  car- 
bonate of  ammonia.  The  barren  soil  on  the 
coast  of  Peru  is  rendered  fertile  by  means  of 
a  manure  called  Guano,  which  is  collected 
from  several  islands  in  the  South  Sea.*  It 
is  sufficient  to  add  a  small  quantity  of  guano 

*  The  guano,  which  forms  a  stratum  several 
feet  in  thickness  upon  the  surface  of  these  islands, 
consists  of  the  putrid  excrements  of  innumerable 

P 


'to  a  soil,  which  consists  only  of  sand  and 
'  clay,  in  order  to  procure  the  richest  crop  of 
maize.  The  soil  itself  does  not  contain  the 
smallest  particle  of  organic  matter,  and  the 
manure  employed  is  formed  only  of  urate, 
phospliate,  oxalate,  and  carbonate  of  ammonia, 
together  with  a  few  earthy  salts."* 

Ammonia,  therefore,  must  have  yielded 
the  nitrogen  to  these  plants.  Gluten  is  ob- 
tained not  only  from  corn,  but  also  from 
grapes  and  other  plants ;  but  that  extracted 
from  the  grapes  is  called  vegetable  albumen, 
although  it  is  identical  in  composition  and 
properties  with  the  ordinary  gluten. 

It  is  ammonia  which  yields  nitrogen  to 
the  vegetable  albumen,  the  principal  con- 
stituent of  plants  ;  and  it  must  be  ammonia 
which  forms  the  red  and  blue  colouring 
matters  of  flowers.  Nitrogen  is  not  pre- 
sented to  wild  plants  in  any  other  form  ca- 
pable of  assimilation.  Ammonia,  by  its 
transformation,  furnishes  nitric  acid  to  the 
tobacco  plant,  sun-flower,  Chenopodium,  and 
Borago  ojficinalis,  when  they  grow  in  a 
soil  completely  free  from  nitre.  Nitrates 
are  necessary  constituents  of  these  plants, 
which  thrive  only  when  ammonia  is  present 
in  large  quantity,  and  when  they  are  also 
subject  to  the  influence  of  the  direct  rays  of 
the  sun,  an  influence  necessary  to  effect  the 
disengagement  within  their  stem  and  leaves 
of  the  oxygen,  which  shall  unite  with  the 
ammonia  to  form  nitric  acid. 

The  urine  of  men  and  of  carnivorous 
animals  contains  a  large  quantity  of  nitrogen, 
partly  in  the  form  of  phosphates,  partly  as 
urea.  Urea  is  converted  during  putrefac- 
tion into  carbonate  of  ammonia,  that  is  to 
say,  it  takes  the  form  of  the  very  salt  which 
occurs  in  rain-water.  Human  urine  is  the 
most  powerful  manure  for  all  vegetables 
containing  nitrogen;  that  of  horses  and 
horned  cattle  contains  less  of  this  element, 
but  infinitely  more  than  the  solid  excrements 
of  these  animals.  In  addition  to  urea,  the 
urine  of  herbivorous  animals  contains  hip- 
puric  acid  which  is  decomposed  during  pu  • 
[refaction  into  benzoic  acid  and  ammonia. 
The  latter  enters  into  the  composition  of  the 
luten,  but  the  benzoic  acid  often  remains 
unchanged:  for  example,  in  the  Jlntlwxan 
thum  odoratum. 

The  solid  excrements  of  animals  contain 
omparatively  very  little  nitrogen,  but  this 
could  not  be  otherwise.  The  food  taken  by 
animals  supports  them  only  in  so  far  as  it 
offers  elements  for  assimilation  to  the  various 
organs  which  they  may  require  fcx  their 
ncrease  or  renewal.  Corn,  grass,  ami  all 
slants,  without  exception,  contain  azotised 
substances.  The  quantity  of  food  which 
animals  take  for  their  nourishment,  dimi- 
nishes or  increases  in  the  same  proportion 
as  it  contains  more  or  less  of  the  substances 
containing  nitrogen.  A  horse  may  be  kept 


sea  fowl  that  remain  on  them  during  the  breeding 
season.     See  the  Chapter  on  Manures.) 

*  Boussingault,  Ann.  de  Ch.  et  de  Phys.  Lxv.  p. 
319. 


34 


AGRICULTURAL   CHEMISTRY. 


alive  by  feeding  it  with  potatoes,  which  con- 
tain a  very  small  quantity  of  nitrogen  ;  but 
life  thus  supported  is  a  gradual  starvation; 
the  animal  increases  neither  in  size  nor 
strength,  and  sinks  under  every  exertion. 
The  quantity  of  rice  which  an  Indian  eats 
astonishes  the  European ;  but  the  fact  that 
rice  contains  less  nitrogen  than  any  other 
kind  of  grain  at  once  explains  the  circum- 
stance. 

Now,  as  it  is  evident  that  the  nitrogen  of 
the  plants  and  seeds  used  by  animals  as  food 
must  be  employed  in  the  process  of  assimila- 
tion, it  is  natural  to  expect  that  the  excre- 
ments of  these  animals  will  be  deprived  of  it 
in  proportion  to  the  perfect  digestion  of  the 
food,  and  can  only  contain  it  when  mixed 
with  secretions  from  the  liver  and  intestines. 
Under  all  circumstances,  they  must  contain 
less  nitrogen  than  the  food.  When,  there- 
fore, a  field  is  manured  with  animal  excre- 
ments, a  smaller  quantity  of  matter  contain- 
ing nitrogen  is  added  to  it  than  has  been 
taken  from  it  in  the  form  of  grass,  herbs,  or 
seeds.  By  means  of  manure,  an  addition 
only  is  made  to  the  nourishment  which  the 
air  supplies. 

In  a  scientific  point  of  view,  it  should  be 
the  care  of  the  agriculturist  so  to  employ  all  | 
the  substances  containing  a  large  proportion 
of  nitrogen  which  his  farm  affords  in  the 
form  of  animal  excrements,  that  they  shall 
serve  as  nutriment  to  his  own  plants.    This 
will  not  be  the  case  unless  those  substances  i 
are  properly  distributed  upon  his  land.     A 
heap  of  manure  lying  unemployed  upon 
his  land  would  serve  him  no  more  than  his 
neighbours.     The  nitrogen  in  it  would  es-  | 
cape  as  carbonate  of  ammonia  into  the  at- 
mosphere,  and  a  mere  carbonaceous  residue 
of  decayed  plants  would,  after  some  years, 
be  found  in  its  place. 

All  animal  excrements  emit  carbonic  acid 
and  ammonia,  as  long  as  nitrogen  exists  in 
them.     In  every  stage  of  their  putrefaction 
an  escape  of  ammonia  from  them  may  be 
induced  by  moistening  them  with  a  potash 
ley ;   the  ammonia  being   apparent  to  the  j 
senses  by  a  peculiar  smell,  and  by  the  dense  j 
white  vapour  which  arises  when  a  solid 
body  moistened  with  an  acid  is  brought  near 
it.     This  ammonia  evolved  from  manure  is 
imbibed  by  the  sojl  either  in  solution  in  ! 
water,  or  m  the  gaseous  form,  and  plants 
thus  receive  a  larger  supply  of  nitrogen 
than  is  afforded  to  them  by  the  atmosphere. 

But  it  is  much  less  the  quantity  of  am- 
monia, yielded  to  a  soil  by  animal  excre- 
ments, than  the  form  in  which  it  is  presented 
by  them,  that  causes  their  great  influence 
on  its  fertility.  Wild  plants  obtain  more 
nitrogen  from  the  atmosphere  in  the  form  of 
ammonia  than  they  require  for  their  growth, 
for  the  water  which  evaporates  through  their 
leaves  and  blossoms,  emits,  after  some  time, 
a  putrid  smell,  a  peculiarity  possessed  only 
by  such  bodies  as  contain  nitrogen.  Culti- 
vated plants  receive  the  same  quantity  of 
nitrogen  from  the  a'.mospnsre  as  trees, 


shrubs,  and  other  wild  plants;  but  this  is 
not  sufficient  for  the  purposes  of  agricul- 
ture. Agriculture  differs  essentially  from 
the  cultivation  of  forests,  inasmuch  as  its 
principal  object  consi  ts  in  the  production 
of  nitrogen  under  any  form  capable  of  as- 
similation ',  whilst  the  object  of  forest  culture 
is  confined  principally  to  the  production  of 
carbon.  All  the  various  means  of  culture 
are  subservient  to  these  two  main  purposes. 
A  part  only  of  the  carbonate  of  ammonia 
which  is  conveyed  by  rain  to  the  soil  is  re- 
ceived by  plants,  because  a  certain  quantity 
of  it  is  volatilised  with  the  vapour  of  water : 
only  that  portion  of  it  can  be  assimilated 
which  sinks  deeply  into  the  soil,,  or  wlucn 
is  conveyed  directly  to  the  leaves  by  dew,  or 
is  absorbed  from  the  air  along  with  the  car- 
bonic acid. 

Liquid  animal  excrements,  such  as  the 
urine  with  which  the  solid  excrements  are 
impregnated,  contain  the  greatest  part  ot 
their  ammonia  in  the  state  of  salts,  in  a  form, 
therefore,  in  which  it  has  completely  lost  its 
volatility ;  when  presented  in  this  condition, 
not  the  smallest  portion  of  the  ammonia  is 
lost  to  the  plants;  it  is  all  dissolved  by  water, 
and  imbibed  by  their  roots.  The  evident 
influence  of  gypsum  upon  the  growth  of 
grasses — the  striking  fertility  and  luxuriance 
of  a  meadow  upon  which  it  is  strewed — 
depends  only  upon  its  fixing  in  the  soil  the 
ammonia  of  the  atmosphere,  which  would 
otherwise  be  volatilized,  with  the  water 
which  evaporates.*  The  carbonate  of  am- 
monia contained  in  rain-water  is  decom- 
posed by  gypsum,  in  precisely  the  same 
manner  as  in  the  manufacture  of  sal-am- 
moniac. Soluble  sulphate  of  ammonia  and 
carbonate  of  lime  are  formed ;  and  this  salt 
of  ammonia  possessing  no  volatility  is  con- 
sequently retained  in  the  soil.  All  the  gyp- 
sum gradually  disappears,  but  its  action 
upon  the  carbonate  of  ammonia  continues 
as  long  as  a  trace  of  it  exists. 

The  beneficial  influence  of  gypsum  and  of 
many  other  salts  has  been  compared  to  that 
of  aromatics,  which  increase  the  activity  of 
the  human  stomach  and  intestines,  and  give 
a  tone  to  the  whole  system.  But  plants  con- 
tain no  nerves  ;  we  know  of  no  substance 
capable  of  exciting  them  to  intoxication  and 
madness,  or  of  lulling  them  to  sleep  and  re- 
pose. No  substance  can  possibly  cause  their 
leaves  to  appropriate  a  greater  quantity  of 
carbon  from  the  atmosphere,  when  the  other 
constituents  which  the  seeds,  roots,  and 
leaves  require  for  their  growth  are  wanting. 
The  favourable  action  of  small  quantities  of 
aromatics  upon  man,  when  mixed  with  his 
food,  is  undeniable ;  but  aromatics  are  given 
to  plants  without  food  to  be  dig°sted,  and 
still  they  flourish  with  greater  luxuriance. 


*  It  has  long  been  the  practice  in  some  parts  of 
the  country  to  strew  the  floors  of  stables  with 
gypsum.  This  prevents  the  disagreeable  odour 
arising  from  the  putrefaction  of  stable  manure,  by 
decomposing  the  ammouiacai  saks  which  are 
formed. — ED. 


ASSIMILATION  OF  NITROGEN. 


35 


It  is  quite  evident,  therefore,  that  the 
common  view  concerning  the  influence  of 
certain  salts  upon  the  growth  of  plants 
evinces  only  ignorance  of  its  cause. 

The  action  of  gypsum  or  chloride  of  cal- 
cium really  consists  in  their  giving  a  fixed 
condition  to  the  nitrogen — or  ammonia 
which  is  brought  into  the  soil,  and  which  is 
indispensable  for  the  nutrition  of  plants. 

In  order  to  form  a  conception  of  the  effect 
of  gypsum,  it  may  be  sufficient  to  remark 
that  110  Ibs.  of  burned  gypsum  fixes  as 
much  ammonia  in  the  soil  as  6880  Ibs.  of 
horse's  urine*  would  yield  to  it,  even  on  the 
supposition  that  all  the  nitrogen  of  the  urea 
and  hippuric  acid  were  absorbed  by  the 
plants  without  the  smallest  loss,  in  the  form 
of  carbonate  of  ammonia.  If  we  admit  with 
Boussingaultf  that  the  nitrogen  in  grass 
amounts  to  y^  of  its  weight,  then  every 
pound  of  nitrogen  which  we  add  increases 
the  produce  of  the  meadow  100  Ibs.,  and 
this  increased  produce  of  100  Ibs.  is  effected 
by  the  aid  of  a  little  more  than  4  Ibs.  of 
gypsum. 

Water  is  absolutely  necessary  to  effect  the 
decomposition  of  the  gypsum,  on  account 
of  its  difficult  solubility,  (1  part  of  gypsum 
requires  400  parts  of  water  for  solution)  and 
also  to  assist  in  the  absorption  of  the  sul- 
phate of  ammonia  by  the  plants :  hence  it 
happens,  that  the  influence  of  gypsum  is 
not  observable  on  dry  fields  and  meadows. 
In  such  it  would  be  advisable  to  employ  a 
salt  of  more  easy  solubility,  such  as  chloride 
of  calcium. 

The  decomposition  of  gypsum  by  carbo- 
nate of  ammonia  does  not  take  place  instan- 
taneously ;  on  the  contrary,  it  proceeds  very 
gradually,  and  this  explains  why  the  action 
of  the  gypsum  lasts  for  several  years. 

The  advantage  of  manuring 'fields  with 
burned  clay,  and  the  fertility  of  ferruginous 
soils,  which  have  been  considered  as  facts 
so  incomprehensible,  may  be  explained  in 
an  equally  simple  manner.  They  have  been 
ascribed  to  the  great  attraction  for  water, 
exerted  by  dry  clay  and  ferruginous  earth  j 
but  common  dry  arable  land  possesses  this 
property  in  as  great  a  degree  :  and  besides, 
what  influence  can  be  ascribed  to  a  hundred 
pounds  of  water  spread  over  an  acre  of 
land,  in  a  condition  in  which  it  cannot  be 
serviceable  either  by  the  roots  or  leaves  ? 
The  true  case  is  this  : — 

The  oxides  of  iron  and  alumina  are  dis- 
tinguished from  all  other  metallic  oxides  by 
their  power  of  forming  solid  compounds 
with  ammonia.  The  precipitates  obtained 
by  the  addition  of  ammonia  to  salts  of  alu- 


*  The  urine  of  the  horse  contains,  according  to 
Fourcroy  and  Vauquelin,  in  1000  parts, 

Urea 7  parts. 

Hippurate  of  soda  .     .   24  " 
Salts  and  water    .    .  979  " 

1000  parts. 

t  Bonssingault,  Ann.  de  Ch.  et  de  Phys.  t.  Ixiii. 
page  243. 


mina  or  iron  are  true  salts,  in  wnich  the 
ammonia  is  contained  as  a  base.  Minerals 
containing  alumina  or  oxide  of  iron  also 
possess,  in  an  eminent  degree,  the  remark 
able  property  of  attracting  ammonia  from 
the  atmosphere  and  of  retaining  it.  Vau- 
quelin, whilst  engaged  in  the  trial  of  a  crimi- 
nal case,  discovered  that  all  rust  of  iron 
contains  a  certain  quantity  of  ammonia. 
Chevalier  afterwards  found  that  ammonia 
is  a  constituent  of  all  minerals  containing 
iron  ;  that  even  hematite,  a  mineral  which 
is  Dot  at  all  porous,  contains  one  per  cent, 
of  it.  Bouis  showed  also,  that  the  peculiar 
odour  observed  on  moistening  minerals  con- 
taining alumina,  is  partly  owing  to  their  ex- 
haling ammonia.  Indeed,  gypsum  and 
some  varieties  of  alumina,  pipe-clay  for  ex- 
ample, emit  so  much  ammonia,  when  mois- 
tened with  caustic  potash,  that  even  after 
they  had  been  exposed  for  two  days,  red- 
dened litmus  paper  held  over  them  becomes 
blue.  Soils,  therefore,  which  contain  ox- 
ides of  iron,  and  burned  clay,  must  absorb 
ammonia,  an  action  which  is  favoured  by 
their  porous  condition  ;  they  further  prevent 
the  escape  of  the  ammonia  once  absorbed 
by  their  chemical  properties.  Such  soils, 
in  fact,  act  precisely  as  a  mineral  acid  would 
do,  if  extensively  spread  over  their  surface  ; 
with  this  difference,  that  the  acid  would  pe- 
netrate the  ground,  enter  into  combination 
with  lime,  alumina,  and  other  bases,  and 
thus  lose,  in  a  few  hours,  its  property  of 
absorbing  ammonia  from  the  atmosphere. 
The  addition  of  burned  clay  to  soils  has  also 
a  secondary  influence;  it  renders  the  soil 
porous,  and,  therefore,  more  permeable  to 
air  and  moisture. 

The  ammonia  absorbed  by  the  clay  or  fer- 
ruginous oxides  is  separated  by  every  shower 
of  rain,  and  conveyed  in  solution  to  the  soil. 

Powdered  charcoal  possesses  a  similar  ac- 
tion, but  surpasses  all  other  substances  in 
the  power  which  it  possesses  of  condensing 
ammonia  within  its  pores,  particularly  when 
it  has  been  previously  heated  to  redness. 
Charcoal  absorbs  90  times  its  volume  of  am- 
moniacal  gas,  which  may  be  again  separated 
by  simply  moistening  it  with  water.  (De 
Saussure.)  Decayed  wood  approaches  very 
nearly  to  charcoal  in  this  power ;  decayed 
oak  wood  absorbs  72  times  its  volume,  after 
having  been  completely  dried  under  the  air- 
pump.  We  have  here  an  easy  and  satisfac- 
tory means  of  explaining  still  further  the  pro- 
perties of  humus,  or  wood  in  a  decaying 
state.  It  is  not  only  a  slow  and  constant 
source  of  carbonic  acid,  but  it  is  also  a 
means  by  which  the  necessary  nitrogen  is 
convey  eel  to  plants. 

Nitrogen  is  found  in  lichens,  which  grow 
on  basaltic  rocks.  Our  fields  produce  more 
of  it  than  we  have  given  them  as  manure, 
and  it  exists  in  all  kinds  of  soils  and  mine- 
rals which  were  never  in  contact  with  or- 
ganic substances.  The  nitrogen  in  these 
cases  could  only  have  been  extracted  from 
the  atmosphere. 


36 


AGRICULTURAL    CHEMISTRY, 


We  find  this  nitrogen  in  the  atmosphere, 
in  rain  water,  and  in  all  kinds  of  soils,  in 
the  form  of  ammonia,  as  a  product  of  the 
decay  and  putrefaction  of  preceding  genera- 
tions of  animals  and  vegetables.  We  find 
likewise  that  the  proportion  of  azotised  mat- 
ters in  plants  is  augmented  by  giving  them  a 
larger  supply  of  ammonia  conveyed  in  the 
form  of  animal  manure. 

No  conclusion  can  then  have  a  better 
foundation  than  this,  that  it  is  the  ammonia 
of  the  atmosphere  which  furnishes  nitrogen 
to  plants. 

Carbonic  acid,  water  and  ammonia,  con- 
tain the  elements  necessary  for  the  support 
of  animals  and  vegetables.  The  same  sub- 
stances are  the  ultimate  products  of  the 
chemical  processes  of  decay  and  putrefac- 
tion. All  the  innumerable  products  of  vi- 
tality resume,  after  death,  the  original  form 
from  which  they  sprung.  And  thus  death — 
the  complete  dissolution  of  an  existing 
generation — becomes  the  source  of  life  for  a 
new  one. 


CHAPTER  VI. 

p 

OF    THE    INORGANIC    CONSTITUENTS    OF 
PLANTS. 

CARBONIC  acid,  water  and  ammonia,  are 
necessary  for  the  existence  of  plants,  be- 
cause they  contain  the  elements  from  which 
their  organs  are  formed ;  but  other  sub- 
stances are  likewise  requisite  for  the  forma- 
tion of  certain  organs  destined  for  special 
functions  peculiar  to  each  family  of  plants. 
Plants  obtain  these  subtances  from  inorganic 
nature.  In  the  ashes  left  after  the  incinera- 
tion of  plants,  the  same  substances  are 
found,  although  in  a  changed  condition. 

Although  the  vital  principle  exercises  a 
great  power  over  chemical  forces,  yet  it 
does  so  only  by  directing  the  way  in  which 
they  are  to  act,  and  not  by  changing  the 
laws  to  which  they  are  subject.  Hence 
when  the  chemical  forces  are  employed  in 
the  processes  of  vegetable  nutrition,  they 
must  produce  the  same  results  which  are 
observed  in  ordinary  chemical  phenomena. 
The  inorganic  matter  contained  in  plants 
must,  therefore,  be  subordinate  to  the  laws 
which  regulate  its  combinations  in  common 
chemical  processes. 

The  most  important  division  of  inorganic 
substances  is  that  of  acids  and  alkalies.  Both 
of  these  have  a  tendency  to  unite  together, 
and  form,  neutral  compounds,  which  are 
termed  salts.  According  to  the  doctrine  of 
equivalents,  these  combinations  are  always 
effected  in  definite  proportions,  that  is  to 
eay,  one  equivalent  of  an  acid  always  unites 
with  one  or  two  equivalents  of  a  base,  v/hat- 
ever  that  base  may  be.  Thus  501 -I/  parts 
by  weight  of  sulphuric  acid  unite  with  1  eq. 
of  potash,  and  form  one  eq.  of  sulphate  of 
pc  lash;  the  same  quantity  unites  with  1  eq. 


of  soda,  and  produces  sulphate  of  soda 
From  this  fact  follows  the  rule — that  the 
quantity,  which  an  acid  requires  of  an  alkali 
for  its  saturation,  may  be  represented  by  a 
very  simple  number. 

It  is  perfectly  necessary  to  form  a  proper 
conception  of  what  chemists  denominate 
the  "capacity  for  saturation  of  an  acid," 
before  we  are  able  to  form  a  correct  idea  of 
the  functions  performed  in  plants,  by  their 
inorganic  constituents.  The  power  of  a 
base  to  neutralize  an  acid  does  not  depend 
upon  the  quantity  of  radical  which  it  con- 
tains, but  altogether  upon  the  quantity  of  its 
oxygen.  Thus  protoxide  of  iron  contains 
1  eq.  of  oxygen,  and  unites  with  1  eq.  of 
sulphuric  acid  in  forming  a  neutral  salt;  but 
peroxide  of  iron  contains  3  eq.  of  oxygen, 
and  requires  3  eq.  of  the  same  acid  for  its 
neutralization.  Hence  when  a  given  weight 
of  an  acid  is  neutralized  by  different  bases, 
the  quantity  of  oxygen  contained  in  these 
bases  must  be  the  same  as  is  exhibited  by 
the  following  scale : — 

501*17  parts  of  Sulphuric  Acid  neutralize 

258-35  Magnesia  Oxygen=  100 

647-29  Strontia  "   =100 

1451-61  Oxide  of  Silver  "   =100 

956-8    Barytes  "   =100 

It  follows  from  the  law  of  equivalents, 
that  the  quantity  of  oxygen  in  a  base  must 
stand  in  a  simple  relation  to  the  quantity  of 
oxygen  in  an  acid  which  unites  with  it.  By 
this  is  meant,  that  the  quantities  in  both  cases 
must  either  be  equal  or  multiples  of  each 
other;  for  the  doctrine  of  equivalents  denies 
the  possibility  of  their  uniting  in  fractional 
parts.  This  will  be  rendered  obvious  by  a 
consideration  of  the  two  following  exam- 
ples: 

100  parts  of  Cyanic  Acid  contain  23'26  oxy- 
gen =  1. 

100  parts  of  Cyanic  Acid  saturate  137'21  parts  of 
potash,  which  contain  23*26  oxygen  =1. 

100  parts  of  Nitric  Acid  contain  73*85  oxygen  =5. 

100  parts  of  Nitric  Acid  saturate  214*40  parts  of 
oxide  of  silver,  which  contain  14'77  oxygen  =  1. 

In  the  first  of  these  cases,  the  relation  of 
the  oxygen  of  the  base  to  that  of  the  acid  is 
as  1:1 ;  in  the  second,  as  1:5.  The  capacity 
for  saturation  of  each  acid,  is,  therefore,  the 
constant  quantity  of  oxygen  necessary  to 
neutralize  190  parts  of  it. 

Many  of  the  inorganic  constituents  vary 
according  to  the  soil  in  which  the  plants 
grow,  but  a  certain  number  of  them  are  in- 
dispensable to  their  developement.  All  sub- 
stances in  solution  in  a  soil  are  absarbed  by 
the  roots  of  plants,  exactly  as  a  sponge  im- 
bibes a  liquid,  and  all  that  it  contains,  with- 
out selection.  The  substances  thus  con- 
veyed to  plants  are  retained  in  greater  or 
less  quantity,  or  are  entirely  separated  when 
not  suited  for  assimilation. 

Phosphace  of  magnesia  in  combination 
with  ammonia  is  an  invariable  constituent 
of  the  seeds  of  all  kinds  of  grasses.  It  "> 
contained  in  the  outer  horny  husk,  and  is 
introduced  into  bread  along  with  the  flour, 


CONSTITUENTS    OF    PLANTS. 


37 


and  also  into  beer.  The  bran  of  flour  con- 
tains the  greatest  quantity  of  it.  It  is  this 
salt  which  forms  large  crystalline  concre- 
tions, often  amounting  to  several  pounds  in 
weight,  in  the  ccecwn  of  horses  belonging 
to  millers;  and  when  ammonia  is  mixed 
with  beer,  the  same  salt  separates  as  a  white 
precipitate. 

Most  plants,  perhaps  all  of  them,  contain 
organic  acids  of  very  different  composition 
and  properties,  all  of  which  are  in  combi- 
nation with  bases,  such  as  potash,  soda, 
lime,  or  magnesia.  These  bases  evidently 
regulate  the  formation  of  the  acids,  for  the 
diminution  of  the  one  is  followed  by  a  de- 
crease of  the  other:  thus  in  the  grape,  for 
example,  the  quantity  of  potash  contained 
in  its  juice  is  less  when  it  is  ripe  than  when 
unripe ;  and  the  acids,  under  the  same 
circumstances,  are  found  to  vary  in  a 
similar  manner.  Such  constituents  exist  in 
small  quantity  in  those  parts  of  a  plant  in 
which  the  process  of  assimilation  is  most 
active,  as  in  the  mass  of  woody  fibre;  and 
their  quantity  is  greater  in  those  organs 
whose  office  it  is  to  prepare  substances  con- 
veyed to  them  for  assimilation  by  other 
parts.  The  leaves  contain  more  inorganic 
matters  than  the  branches,  and  the  branches 
more  than  the  stem.  The  potato  plant  con- 
tains more  potash  before  blossoming  than 
after  it. 

The  acids  found  in  the  different  families 
of  plants  are  of  various  kinds ;  it  cannot  be 
supposed  that  their  presence  and  peculiari- 
ties are  the  result  of  accident.  The  fumaric 
and  oxalic  acids  in  the  liverwort,  the  kinovic 
acid  in  the  China  nova,  the  rocellic  acid  in 
the  Rocella  linctoria,  the  tartaric  acid  in 
grapes,  and  the  numerous  other  organic 
acids,  must  serve  some  end  in  vegetable  life. 
But  if  these  acids  constantly  exist  in  vege- 
tables, and  are  necessary  to  their  life,  which 
is  incontestable,  it  is  equally  certain  that 
some  alkaline  base  is  also  indispensable,  in 
order  to  enter  into  combination  with  the 
acids  which  are  always  found  in  the  state  of 
salts.  All  plants  yield  by  incineration  ashes 
containing  carbonic  acid;  all  therefore  must 
contain  salts  of  an  organic  acid.* 

Now,  as  we  know  the  capacity  of  satura- 
tion of  organic  acids  to  be  unchanging,  it 
follows  that  the  quantity  of  the  bases  united 
with  them  cannot  vary,  and  for  this  reason 
the  latter  substances  ought  to  be  considered 
with  the  strictest  attention  both  by  the  agri- 
culturist and  physiologist. 

We  have  no  reason  to  believe  that  a  plant 
in  a  condition  of  free  and  unimpeded  growth 
produces  more  of  its  peculiar  acids  than  it 
requires  for  its  own  existence ;  hence,  a 
plant,  on  whatever  soil  it  grows,  must  con- 
tain an  invariable  quantity  of  alkaline  bases. 
Culture  alone  will  be  able  to  cause  a  devia- 
tion. 


*  Snlts  of  organic  acids  yield  carbonates  on  in- 
cineration, if  they  contain  either  alkaline  or  earthy 
bases. 


In  order  to  understand  this  subject  clearly, 
it  will  be  necessary  to  bear  in  mind  that  any 
one  of  the  alkaline  bases  may  be  substituted 
for  another,  the  action  of  all  being  the  same. 
Our  conclusion  is  therefore  by  no  means  en- 
dangered by  the  existence  of  a  particular 
alkali  in  one  plant,  which  may  be  absent  in 
others  of  the  same  species.  If  this  inference 
be  correct,  the  absent  alkali  or  earth  must  be 
supplied  by  one  similar  in  its  mode  of  ac- 
tion, or  in  other  words,  by  an  equivalent  of 
another  base.  The  number  of  equivalents 
of  these  various  bases  which  may  be  com- 
bined with  a  certain  portion  of  acid  must 
necessarily  be  the  same,  and  therefore  the 
amount  of  oxygen  contained  in  them  must 
remain  unchanged  under  all  circumstances 
and  on  whatever  soil  they  grow. 

Of  course,  this  argument  lefers  only  to 
those  alkaline  bases  which  in  the  form  of 
organic  salts  form  constituents  of  the  plants. 
Now,  these  salts  are  preserved  in  the  ashes 
of  plants  as  carbonates,  the  quantity  of 
which  can  be  easily  ascertained. 

It  has  been  distinctly  shown,  by  the  analy 
sis  of  De  Saussure  and  Berthier,  that  the 
nature  of  a  soil  exercises  a  decided  influence 
on  the  quantity  of  the  different  metallic  ox- 
ides contained  in  the  plants  which  grow  on 
it ;  that  magnesia,  for  example,  was  con- 
tained in  the  ashes  of  a  pine-tree  grown  at 
Mont  Breven,  whilst  it  was  absent  from  the 
ashes  of  a  tree  of  the  same  species  from 
Mont  La  Salle,  and  that  even  the  proportion 
of  lime  and  potash  was  very  different. 

Hence  it  has  been  concluded,  (errone- 
ously, I  believe,)  that  the  presence  of  bases 
exercises  no  particular  influence  upon  the 
growth  of  plants :  but  even  were  this  view 
correct,  it  must  be  considered  as  a  most  re- 
markable accident  that  these  same  analyses 
furnish  proof  for  the  very  opposite  opinion. 
For  although  the  composition  of  the  ashes 
of  these  pine-trees  were  so  very  different, 
they  contained,  according  to  the  analyses  of 
De  Saussure,  an  equal  number  of  equiva- 
lents of  metallic  oxides ;  or,  what  is  the  same 
thing,  the  quantity  of  oxygen  contained  in 
all  the  bases  was  in  both  cases  the  same. 

100  parts  of  the  ashes  of  the  pine-tree 
from  Mont  Breven  contained — 


Carbonate  of  Potash 

Lime 

"     Magnesia 


3-60 

46-34 

6-77 


Sum  of  the  carbonates  56'71 

Quantity  of  oxygen  in  the  Potash         0-41 

Lime          733 

"          "        Magnesia  1-27 

Sum  of  the  oxygen  in  the  bases  9*01 

100  parts  of  the  ashes  of  the  pine  from 
Mont  La  Salle  contained* — 


*  According  to  the  experiments  of  Saussure, 
1000  parts  of  the  wood  of  the  pine  from  Mont 
Brevon  gave  11 '87  parts  of  ashes  ;  the  same  quan- 
tity of  wood  from  Mont  La  Salle  yielded  11*28 
parts.  From  this  we  might  conclude  that  the  two 
pines,  although  brought  up  in  different  soils,  yet 
contained  the  same  quantity  of  'inorganic  elements* 


S3 


AGRICULTURAL  CHEMISTRY. 


Carbonate  of  Potash          •         7'36 
Lime  •        51*19 

Magnesia  0000 

Sum  of  the  carbonates  58*55 

Quantity  of  oxygen  in  the  Potash         0'85 

"        Lime         ,8'10 

Sum  of  the  oxygen  in  the  bases  8'95 

The  numbers  9'01  and  8*95  resemble  each 
other  as  nearly  as  could  be  expected  even 
in  analyses  made  for  the  very  purpose  of 
ascertaining  the  fact  above  demonstrated 
which  the  analyst  in  this  case  had  not  in 
view. 

Let  us  now  compare  Berthier's  analyses 
of  the  ashes  of  two  fir-trees,  one  of  which 
grew  in  Norway,  the  other  in  Allevard  (de- 
partement  de  1'isere).  One  contained  50,  the 
other  25  per  cent,  of  soluble  salts.  A  greater 
difference  in  the  proportion  of  the  alkaline 
bases  could  scarcely  exist  between  two  to- 
tally different  plants,  and  yet  even  here  the 
quantity  of  oxygen  in  the  bases  of  both  was 
the  same. 

100  parts  of  the  ashes  of  firwood  from 
Allevard  contained,  according  to  Berthier, 
(Ann.  de  Chim.  et  de  Phys.  t.  xxxii.  p. 
248,) 

Potash  &  Soda  16'8  in  which  3'42  must  be  oxygen. 
Lime        .        29'5         ••       8.20       " 
Magnesia  3'2        "       1.20      "          " 


49.5 


12-82 


Only  part  of  the  potash  and  soda  in  these 
ashes  was  in  combination  with  organic 
acids ;  the  remainder  was  in  the  form  of 
sulphates,  phosphates,  and  chlorides.  One 
nundred  parts  of  the  ashes  contain  3-1  sul- 
pnunc  acid,  4-2  phosphoric  acid,  and  0-3 
hydrochloric  acid,  which  together  neutralize 
a  quantity  of  base  containing  1-20  oxygen. 
This  number  therefore  must  be  substracted 
from  12-82.  The  remainder  11-62  indicates 
the  quantity  of  oxygen  in  the  alkaline 
bases,  combined  with  organic  acids  in  the 
firwood  of  Allevard. 

The  firwood  of  Norway  contained  in  100 
parts, — * 


Potash 
Soda 
Lime 
Magnesia 


14'1    of  which  2-4  would  be  oxygen. 
207  "      5-3        " 

123  "     3'45      "  " 

4-35          "      1-69       "  " 


51-45 


12-84 


And  if  the  quantity  of  oxygen  of  the 
bases  in  combination  with  sulphuric  and 
phosphoric  acid,  viz.  1-37,  be  again  sub- 
stracted from  12-84,  11-47  parts  remain  as 
the  amount  of  oxygen  contained  in  the  bases 
which  were  in  combination  with  organic 
acids. 


*  This  calculation  is  exact  only  in  thfi  case 
where  the  quantity  of  ashes  is  equal  in  weight  for 
a  given  quantity  of  wood  ;  the  difference  cannot, 
however,  be  admitted  to  he  so  great  as  to  change 
sensibly  the  above  proportions  Berthier  has  not 
mentioned  the  proportion  of  ashes  contained  in 
Ihe  wood. 


These  remarkable  approximations  cannot 
be  accidental  ;  and  if  further  examinations 
confirm  them  in  other  kinds  of  plants,  no 
other  explanation  than  that  already  given 
can  be  adopted. 

It  is  not  known  in  what  form  silica,  man 
ganese,  and  oxide  of  iron,  are  contained  in 
plants;  but  we  are  certain  that  potash,  soda, 
and  magnesia,  can  be  extracted  from  all 
parts  of  their  structure  in  the  form  of  salts 
of  organic  acids.  The  same  is  the  case  with 
lime,  when  not  present  as  insoluble  oxalate 
of  lime.  It  must  here  be  remembered,  that 
in  plants  yielding  oxalic  acid,  the  acid  and 
potash  never  exist  in  the  form  of  a  neutral 
or  quadruple  salt,  but  always  as  a  double 
acid  salt,  on  whatever  soil  they  may  grow. 
The  potash  in  grapes  also  is  more  frequently 
found  as  an  acid  salt,  viz.  cream  of  tartar, 
(bitartrate  of  potash,)  than  in  the  form  of  a 
neutral  compound.  As  these  acids  and 
bases  are  never  absent  from  plants,  and  as 
even  the  form  in  which  they  present  them- 
selves is  not  subject  to  change,  it  may  be 
affirmed  that  they  exercise  an  important  in- 
fluence on  the  developement  of  the  fruits  and 
seeds,  and  also  on  many  other  functions  of 
the  nature  of  which  we  are  at  present  igno- 
rant. 

The  quantity  of  alkaline  bases  existing  in 
a  plant  also  depends  evidently  on  this  cir- 
cumstance of  their  existing  only  in  the  form 
of  acid  salts, — for  the  capacity  of  saturation 
of  an  acid  is  constant ;  and  when  we  see 
oxalate  of  lime  in  the  lichens  occupying  the 
place  of  woody  fibre  which  is  absent,  we 
must  regard  it  as  certain  that  the  soluble  or- 
ganic salts  are  destined  to  fulfil  equally  im- 
portant though  different  functions,  so  much 
so  that  we  could  not  conceive  the  complete 
developement  of  a  plant  without  their  pre- 
sence, that  is,  without  the  presence  of  their 
acids,  and  consequently  of  their  bases. 

From  these  considerations  we  must  per- 
ceive, that  exact  and  trustworthy  examina- 
tions of  the  ashes  of  plants  of  the  same  kind 
growing  upon  different  soils  would  be  of  the 
greatest  importance  to  vegetable  physiology 
and  would  decide  whether  the  facts  above 
mentioned  are  the  results  of  an  unchanging 
law  for  each  family  of  plants,  and  whether 
an  invariable  number  can  be  found  to  ex- 
press the  quantity  of  oxygen  which  each 
species  of  plant  contains  in  the  bases  united 
with  organic  acids.  In  all  probability  such 
inquiries  will  lead  to  most  important  results; 
for  it  is  clear  that  if  the  \  reduction  of  a  cer- 
tain unchanging  quantity  of  an  organic  acid 
is  required  by^the  peculiar  nature  of  the 
organs  of  a  plant,  and  is  necessary  to  its  ex- 
istence, then  potash  or  lime  must  be  taken 
up  by  it  in  order  to  form  salts  with  this  acid  ; 
that  if  these  do  not  exist  in  sufficient  quan- 
titv  in  the  soil,  other  bases  must  supply  their 
place;  and  that  the  progress  of  a  plant  must 
be  wholly  arrested  when  none  are  present. 

Seeds  ®f  the  Salsola  Kali,  when  sown  in 
common  garden  soil,  produce  a  plant  con- 
aining  both  potash  and  soda;  while  the 


CONSTITUENTS   OF   PLANTS. 


39 


plains  grown  from  the  seeds  of  this  contain 
only  salts  of  potash,  with  mere  traces  of 
muriate  of  soda.  (Cadet.) 

The  examples  cited  above,  in  which  the 
quantity  of  oxygen  contained  in  the  bases 
was  shown  to  be  the  same,  lead  us  to  the 
legitimate  conclusion  that  the  developement 
of  certain  plants  is  not  retarded  by  the  sub- 
stitution of  the  bases  contained  in  them. 
But  it  was  by  no  means  inferred  that  any 
one  base  could  replace  all  the  others  which 
are  found  in  a  plant  in  its  normal  condition. 
On  the  contrary,  it  is  known  that  certain 
bases  are  indispensable  for  the  growth  of  a 
plant,  and  these  could  not  be  substituted 
without  injuring  its  developement.  Our  in- 
ference has  been  drawn  from  certain  plants, 
which  can  bear  without  injury  this  substitu- 
tion ;  and  it  can  only  be  extended  to  those 
plants  which  are  in  the  same  condition.  It 
will  be  shown  afterwards  that  corn  or  vines 
can  only  thrive  on  soils  containing  potash, 
and  that  this  alkali  is  perfectly  indispensable 
to  their  growth.  Experiments  have  not 
been  sufficiently  multiplied  so  as  to  enable 
us  to  point  out  in  what  plants  potash  or  soda 
may  be  replaced  by  lime  or  magnesia;  we 
are  only  warranted  in  affirming  that  such 
substitutions  are  in  many  cases  common. 
The  ashes  of  various  kinds  of  plants  contain 
very  different  quantities  of  alkaline  bases, 
such  as  potash,  soda,  lime,  or  magnesia. 
When  lime  exists  in  the  ashes  in  large  pro- 
portion, the  quantity  of  magnesia  is  dimi- 
nished, and  in  like  manner  according  as  the 
latter  increases  the  lime  or  potash  decreases. 
In  many  kinds  of  ashes  not  a  trace  of  mag- 
nesia can  be  .detected. 

The  existence  of  vegetable  alkalies  in  com- 
bination with  organic  acids  gives  great 
weight  to  the  opinion  that  alkaline  bases  in 
general  are  connected  with  the  developement 
of  plants. 

If  potatoes  are  grown  where  they  are  not 
supplied  with  earth,  the  magazine  of  inor- 
ganic bases,  (in  cellars,  for  example,)  a  true 
alkali,  called  Solanin,  of  very  poisonous 
nature,  is  formed  in  the  sprouts  which  ex- 
tend towards  the  light,  while  not  the  smallest 
trace  of  such  a  substance  can  be  discovered 
m  the  roots,  herbs,  blossoms,  or  fruits  of 
potatoes  grown  in  fields.  (Otto.)  In  all  the 
species  of  the  Cinchona,  kinic  acid  is  found; 
but  the  quantity  of  quinina,  cinchonina,  and 
lime,  which  they  contain  is  most  variable. 
From  the  fixed  bases  in  the  products  of  in- 
cineration, however,  we  may  estimate  pretty 
accurately  the  quantity  of  the  peculiar  or- 
ganic bases.  A  maximum  of  the  first  cor- 
responds to  a  minimum  of  the  latter,  as 
must  necessarily  be  the  case  if  they  mutually 
replace  one  another  according  to  their  equi- 
valents. We  know  that  different  kinds  of 
opium  contain  meconic  acid  in  combination 
with  very  different  quantities  of  narcotina, 
morphia,  codeia,  &,c.,  the  quantity  of  one 
of  these  alkaloids  diminishingon  the  increase 
of  the  others.  Thus  the  smallest  quantity 
of  morphia  is  accompanied  by  a  maximum 


of  narcotina.  Not  a  trace  of  meconic  acid* 
can  be  discovered  in  many  kinds  of  opium, 
but  there  ib  not  on  tnis  account  an  absence 
of  acid,  for  the  meconic  is  here  replaced  by 
sulphuric  acid.  Her^,  also,  we  have  an  ex- 
ample of  what  has  been  before  slated,  for  in 
those  kinds  of  opium  where  both  these  acids 
exist,  they  are  always  found  to  bear  a  cer- 
tain relative  proportion  to  one  another.  At- 
tention to  these  facts  must  be  very  important 
in  the  selection  of  soils  destined  for  the  cul- 
tivation of  plants  which  yield  the  vegetable 
alkaloids. 

Now  if  it  be  found,  as  appears  to  be  the 
case  in  the  juice  of  poppies,  that  an  organic 
acid  may  be  replaced  by  an  inorganic,  with- 
out impeding  the  growth  of  a  plant,  we  must 
admit  the  probability  of  this  substitution 
taking  place  in  a  much  higher  degree  in  the 
case  of  the  inorganic  bases. 

When  roots  find  their  more  appropriate 
base  in  sufficient  quantity,  they  will  take  up 
less  of  another. 

These  phenomena  do  not  show  themselves 
so  frequently  in  cultivated  plants,  because 
they  are  subjected  to  special  external  condi- 
tions for  the  purpose  of  the  production  of 
particular  constituents  or  particular  organs. 

When  the  soil,  in  which  a  white  hyacinth 
is  growing  in  a  state  of  blossom,  is  sprinkled 
with  the  juice  of  the  Phytolacca  decandra, 
the  white  blossoms  assume  in  one  or  two 
hours  a  red  colour,  which  again  disappears 
after  a  few  days  under  the  influence  of  sun- 
shine, and  they  become  white  and  colourless 
as  before.f  The  juice  in  this  case  evidently 
enters  into  all  parts  of  the  plant,  without 
being  at  all  changed  in  its  chemical  nature, 
or  without  its  presence  being  apparently 
either  necessary  or  injurious.  But  this  con 
dition  is  not  permanent,  and  when  the  bios 
soms  have  again  become  colourless,  none 
of  the  colouring  matter  remains ;  and  if  it 
should  occur  that  any  of  its  elements  were 
adapted  for  the  purposes  of  nutrition  of  the 
plant,  then  these  alone  would  be  retained, 
whilst  the  rest  would  be  excreted  in  an  al- 
tered form  by  the  roots. 

Exactly  the  same  thing  must  happen 
when  we  sprinkle  a  plant  with  a  solution  of 
chloride  of  potassium,  nitre,  or  nitrate  of 
strontia;  they  will  enter  into  the  different 
parts  of  the  p'lant,  just  as  the  coloured  juice 
mentioned  above,  and  will  be  found  in  its 
ashes  if  it  should  be  burnt  at  this  period. 
Their  presence  is  merely  accidental ;  but  no 
conclusion  can  be  hence  deduced  against 
the  necessity  of  the  presence  of  other  bases 
in  plants.  The  experiments  of  Macaire- 
Princep  have  shown,  that  plants  made  to 
vegetate  with  their  roots  in  a  weak  solution 
of  acetate  of  lead,  and  then  in  rain  water, 


*  Robiquet  did  not  obtain  a  trace  of  meconate 
of  lime  from  300  Ibs.  of  opium,  whilst  in  other 
kinds  the  quantity  was  very  considerable.  Ann. 
de  Chim.  liii.  p.  425. 

t  Biot,  in  the  Comptes  rendus  des  Seances  de 
['Academic  des  Sciences,  a  Paris,  ler  Semestre, 
1837,  p.  12. 


40 


AGRICULTURAL   CHEMISTRY. 


yield  to  the  latter  all  the  salt  of  lead  which 
ihey  had  previously  absorbed.  They  return, 
therefore,  to  the  soil  all  matters  which  are 
unnecessary  to  their  existence.  Again,  when 
a  plant,  freely  exposed  to  the  atmosphere, 
rain,  and  sunshine,  is  sprinkled  with  a  solu- 
tion of  nitrate  of  strontia,  the  salt  is  ab- 
sorbed, but  k  is  again  separated  by  the  roots 
and  removed  farther  from  them  by  every 
shower  of  rain,  which  moistens  the  soil,  so 
that  at  last  not  a  trace  of  it  is  to  be  found  in 
the  plant. 

Let  us  consider  the  composition  of  the 
ashes  of  two  lir-trees  as  analysed  by  an  acute 
and  most  accurate  chemist.  One  of  these 
grew  in  Norway,  on  a  soil  the  constituents 
of  which  never  changed,  but  to  which  solu- 
ble salts,  and  particularly  common  salt,  were 
conveyed  in  great  quantity  by  rain-water. 
How  did  it  happen  that  its  ashes  contained 
no  appreciable  trace  of  salt,  although  we  are 
certain  that  its  roots  must  have  absorbed  it 
after  every  shower? 

We  can  explain  the  absence  of  salt  in 
this  case  by  means  of  the  direct  and  positive 
observations  referred  to,  which  have  shown 
that  plants  have  the  power  of  returning  to 
the  soil  all  substances  unnecessary  to  their 
existence;  and  the  conclusion  to  which  all 
the  foregoing  facts  lead  us,  when  their  real 
value  and  bearing  are  apprehended,  is  that 
the  alkaline  bases  existing  in  the  ashes  of 
plants  must  be  necessary  to  their  growth, 
sinoe  if  this  were  not  the  case  they  would 
not  be  retained. 

The  perfect  developement  of  a  plant,  ac- 
cording to  this  view,  is  dependent  on  the 
presence  of  alkalies  or  alkaline  earths ;  for 
when  these  substances  are  totally  wanting 
its  growth  will  be  arrested,  and  when  they 
are  only  deficient  it  must  be  impeded. 

In  order  to  apply  these  remarks,  let  us 
compare  two  kinds  of  trees,  the  wood  of 
which  contains  unequal  quantities  of  alka- 
line bases,  and  we  shall  find  that  one  of 
these  grows  luxuriantly  in  several  soils  upon 
which  the  others  are  scarcely  able  to  vege- 
tate. For  example,  10,000  parts  of  oak 
wood  yield  250  parts  of  ashes,  the  same 
quantity  of  fir  wood  only  83,  of  linden  wood 
500,  of  rye  440,  and  of  the  herb  of  the  po- 
tato plant  1500  parts.* 

Firs  and  pines  find  a  sufficient  quantity 
of  alkalies  in  granitic  and  barren  sandy  soils 
in  which  oaks  will  not  grow ;  and  wheat 
thrives  in  soils  favourable  for  the  linden 
tree,  because  the  bases  which  are  necessary 
to  bring  it  to  complete  maturity,  exist  there 
in  sufficient  quantity.  The  accuracy  of 
these  conclusions,  so  highly  important  to 
agriculture  and  to  the  cultivation  of  forests, 
can  be  proved  by  the  most  evident  facts. 

All  kinds  of  grasses,  the  Equisetacece,  for 
example,  contain  in  the  outer  parts  of  their 
leaves  and  stalk  a  large  quantity  of  silicic 
acid  and  potash  in  the  form  of  acid  silicate 


*  Berthier,  Annalos  de  Chimie  et  de  Physique, 
f.  xxx.  p.  248. 


of  potash.  The  proportion  of  this  salt  does 
not  vary  perceptibly  in  the  soil  of  corn-fields, 
because  it  is  again  conveyed  to  them  as  ma- 
nure in  the  form  of  putrefying  straw.  But 
this  is  not  the  case  in  a  meadow,  and  hence 
we  never  find  a  luxuriant  crop  of  grass*  on 
sandy  and  calcareous  soils,  which  contain 
little  potash,  evidently  because  one  of  the 
constituents  indispensable  to  the  growth  of 
the  plants  is  wanting.  Soils  formed  from 
basalt,  gfauwacke,  and  porphyry  are,  cceteri* 
paribus,  the  best  for  meadow  land,  on  ac- 
count of  the  quantity  of  potash  which  enters 
into  their  composition.  The  potash  ab- 
stracted by  the  plants  is  restored  during  the 
annual  irrigation.  The  potash  contained  in 
the  soil  itself  is  inexhaustible  in  comparison 
with  the  quantity  removed  by  plants.  But 
when  we  increase  the  crop  of  grass  in  a 
meadow  by  means  of  gypsum,  we  remove 
a  greater  quantity  of  potash  with  the  hay 
than  can  under  the  same  circumstances  be 
restored.  Hence  it  happens  that,  after  the 
lapse  of  several  years,  the  crops  of  grass  on 
the  meadows  manured  with  gypsum  dimi- 
nish, owing  to  the  deficiency  of  potash.  But 
if  the  meadow  be  strewed  from  time  to  time 
with  wood-ashes,  even  with  the  lixiviated 
ashes  which  have  been  used  by  soap-boilers, 
(in  Germany  much  soap  is  made  from  the 
ashes  of  wood,^  then  the  grass  thrives  as 
luxuriantly  as  before.  The  ashes  are  only 
a  means  of  restoring  the  potash. 

A  harvest  of  grain  is  obtained  every  thirty 
or  forty  years  from  the  soil  of  the  Luneburg 
heath,  by  strewing  it  with  the  ashes  of  the 
heath  plants  (.Erica  vul^aris}  which  grow 
on  it.  These  plants  during  the  long  period 
just  mentioned  collect  the  potash  and  soua, 
which  are  conveyed  to  them  by  rain-water; 
and  it  is  by  means  of  these  alkalies  that  oats, 
barley,  and  rye,  to  which  they  are  indis- 
pensable, are  enabled  to  grow  on  this  sandy 
heath. 

The  woodcutters  in  the  vicinity  of  Heidel 
berg  have  the  privilege  of  cultivating  the 
soil  for  their  own  use,  after  felling  the  trees 
used  for  making  tan.  Before  sowing  the 
land  thus  obtained,  the  branches,  roots,  and 
leaves,  are  in  every  case  burned,  and  the 
ashes  used  as  a  manure,  which  is  found  to 
be  quite  indispensable  for  the  growth  of  the 
grain.  The  soil  itself  upon  which  the  oats 
grow  in  this  district  consists  of  sandstone ; 
and  although  the  trees  find  in  it  a  quantity 
of  alkaline  earths  sufficient  for  their  own 
sustenance,  yet  in  its  ordinary  condition  it  is 
incapable  of  producing  grain. 

The  most  decisive  proof  of  the  use  of  strong 
manure  was  obtained  at  Bingen  (a  town  on 
the  Rhine,)  where  the  produce  and  deve- 
lopement of  vines  were  highly  increased  by 


*  It  would  be  of  importance  to  examine  what 
alkalies  are  contained  in  the  ashes  of  the  sea-shore 
plants  which  grow  in  the  humid  hollows  of  downs, 
and  especially  in  those  of  the  millet-grass.  If 
potash  is  not  found  in  them,  it  must  certainly  bf> 
replaced  by  soda  as  in  the  Salsola,  or  by  lime  aa 
in  the  PlumbaginecB. 


CONSTITUENTS    OF    PLANTS. 


41 


manuring  them  with  such  substances  as  shav- 1 
ings  of  horn,  Sec. ;  but  after  some  years  the  ' 
formation  of  the  wood  and  leaves  decreased  j 
to  the  great  loss  of  the  possessor,  to  such  a  | 
degree  that  he  has  long  had  cause  to  regret 
his  departure  from  the  usual  methods.     By 
the  manure  employed  by  him,  the  vines  had 
been  too  much  hastened  in  their  growth  ;  in 
two  or  three  years  they  had  exhausted  the 
potash  in  the  formation  of  their  fruit,  leaves, 
and  wood,  so  that  none  remained  for  the  fu- 
ture crops,  his  manure  not  having  contained 
any  potash. 

There  are  vineyards  on  the  Rhine  the 
plants  of  which  are  a  hundred  years  old, 
and  all  of  these  have  been  cultivated  by 
manuring  them  with  a  cow-dung,  a  manure 
containing  a  large  proportion  of  potash, 
although  very  little  nitrogen.  All  the  potash, 
in  fact,  which  is  contained  in  the  food  con- 
sumed by  a  cow  is  again  immediately  dis- 
charged in  its  excrements. 

The  experience  of  a  proprietor  of  land  in 
the  vicinity  of  Gottingen  offers  a  most  re- 
markable example  of  the  incapability  of  a 
soil  to  produce  wheat  or  grasses  in  general, 
when  it  fails  in  any  one  of  the  materials  ne- 
cessary to  their  growth.  In  order  to  obtain 
potash,  he  planted  his  whole  land  with 
wormwood,  the  ashes  of  which  are  well 
known  to  contain  a  large  proportion  of  the 
carbonate  of  that  alkali.  The  consequence 
was,  that  he  rendered  his  land  quite  incapa- 
ble of  bearing  grain  for  many  years,  in  con- 
sequence of  having  entirely  deprived  the 
soil  of  its  potash. 

The  leaves  and  small  branches  of  trees 
contain  the  most  potash;  and  the  quantity 
of  them  which  is  annually  taken  from  a 
wood  for  the  purpose  of  being  employed  as 
litter,*  contain  more  of  that  alkali  than  all 
the  old  wood  which  is  cut  down.  The 
bark  and  foliage  of  oaks,  for  example,  con- 
tain from  6  to  9  per  cent,  of  this  alkali ;  the 
needles  of  firs  and  pines,  8  per  cent. 

With  every  2650  Ibs.  of  firwood  which 
are  yearly  removed  from  an  acre  of  forest, 
only  from  (H14  to  0'53  Ibs.  of  alkalies  are 
abstracted  from  the  soil,  calculating  the 
ashes  at  O83  per  cent.  The  moss,  however, 
which  covers  the  ground,  and  of  which  the 
ashes  are  known  to  contain  so  much  alkali, 
continues  uninterrupted  in  its  growth,  and 
retains  that  potash  on  the  surface,  which 
would  otherwise  so  easily  penetrate  with 
the  rain  through  the  sandy  soil.  By  its  de- 
cay, an  abundant  provision  of  alkalies  is 
supplied  to  the  roots  of  the  trees,  and  a  fresh 
supply  is  rendered  unnecessary. 


*  [This  refers  to  a  custom  some  time  since 
very  prevalent  in  Germany  although  now  discon- 
tinued. The  leaves  and  small  twigs  of  trees 
were  gleaned  from  the  forests  by  poor  people,  for 
the  purpose  of  being  used  as  litter  for  their  cattle. 
The  trees,  however,  were  found  to  suffer  so  much 
in  consequence,  that  their  removal  is  strictly  pro- 
hibited. The  cause  of  the  'njury  was  that  stated 
;n  tbe  text. — ED.] 

6 


The  supposition  of  alkalies,  metallic  ox- 
ides, or  inorganic  matter  in  general,  being 
produced  by  plants,  is  entirely  refuted  by 
these  well-authenticated  facts. 

It  is  thought  very  remarkable,  that  those 
plants  of  the  grass  tribe,  the  seeds  of  which 
furnish  food  for  man,  follow  him  like  the 
domestic  animals.  But  saline  plants  seek 
the  sea-shore  or  saline  springs,  and  the 
Chenopodium  the  dunghill  from  similar 
causes.  Saline  plants  require  common  salt, 
and  the  plants  which  grow  only  on  dung- 
hills need  ammonia  and  nitrates,  and  taey 
are  attracted  whither  these  can  be  found, 
just  as  the  dung-fly  is  to  animal  excrements. 
So  likewise  none  of  our  corn-plants  can 
bear  perfect  seeds,  that  is,  seeds  yielding 
flour,  without  a  large  supply  of  phosphate 
of  magnesia  and  ammonia,  substances  which 
they  require  for  their  maturity.  And  hence, 
these  plants  grow  only  in  a  soil  where  these 
three  constituents  are  found  combined,  and 
no  soil  is  richer  in  them  than  those  where 
men  and  animals  dwell  together;  where  the 
urine  and  excrements  of  these  are  found 
corn-plants  appear,  because  their  seeds  can- 
not attain  maturity  unless  supplied  with  the 
constituents  of  those  matters. 

When  we  find  sea-plants  near  our  salt- 
works, several  hundred  miles  distant  from 
the  sea,  we  know  that  their  seeds  have  been 
carried  there  in  a  very  natural  manner, 
namely,  by  wind  or  birds,  which  have 
spread  them  over  the  whole  surface  of  the 
earth,  although  they  grow  only  in  those 
places  in  which  they  find  the  conditions 
essential  to  their  life. 

Numerous  small  fish,  of  not  more  than 
two  inches  in  length  (Gasterosteus  aculeatus,} 
are  found  in  the  salt-pans  of  the  graduating 
house  at  Nidda  (a  village  in  Hesse  Darm- 
stadt.) No  living  animal  is  found  in  the 
salt-pans  of  Neuheim,  situated  about  18 
miles  from  Nidda;  but  the  water  there  con- 
tains so  much  carboriic  acid  and  lime,  tbat 
the  walls  of  the  graduating  house  are  covered 
with  stalactites.  Hence  the  eggs  conveyed 
to  this  place  by  birds  do  not  find  the  condi- 
tions necessary  for  their  developement, 
which  they  found  in  the  former  place.* 


*  The  itch-insect  (Acarus  Scabiei)  is  considered 
by  Burdach  as  the  production  of  a  morbid  condi- 
tion, so  likewise  lice  in  children  ;  the  original 
generation  of  the  fresh-water  muscle  (mytilus)  in 
fish-ponds,  of  sea-plants  in  the  vicinity  of  salt» 
works,  of  nettles  and  grasses,  of  fish  in  pools  of 
rain,  of  trout  in  mountain  streams,  &c.,  is  ac- 
cording to  the  same  natural  philosopher  not  im- 
possible. A  soil  consisting  of  crumbled  rocks, 
decayed  vegetables,  rain  and  salt  water,  &c.,  is 
here  supposed  to  possess  the  power  of  generating 
shell-fish,  trout,  and  saltwort  (salicornia.)  All 
inquiry  is  arrested  by  such  opinions,  when  propa- 
gated by  a  teacher  who  enjoys  a  merited  reputa- 
tion, obtained  by  knowledge  and  hard  labour. 
These  subjects,  however,  have  hitherto  met 
with  the  most  superficial  observation,  although 
they  well  merit  strict  investigation.  The  dark, 
the  secret,  the  mysterious,  the  enigmatic,  is,  in 
fact,  too  seducing  for  the  youthful  and  philosophic 

D  2 


42 


AGRICULTURAL   CHEMISTRY. 


How  much  more  wonderful  and  inexpli 
cable  does  it  appear,  that  bodies  which  re- 
mained fixed  in  the  strong  heat  of  a  fire,  have 
under  certain  conditions  the  property  of 
volatilizing  and,  at  ordinary  temperatures, 
of  passing  into  a  state,  of  which  we  cannot 
say  whether  they  have  really  assumed  the 
form  of  a  gas  or  are  dissolved  in  one !  Steam 
or  vapours  in  general  have  a  very  singular 
influence  in  causing  the  volatilization  of 
such  bodies,  that  is,  of  causing  them  to  as- 
sume the  gaseous  form.  A  liquid  during 
evaporation  communicates  the  power  of  as- 
suming the  same  state  in  a  greater  or  less 
degree  to  all  substances  dissolved  in  it, 
although  they  do  not  of  themselves  possess 
that  property. 

Boracic  acid  is  a  substance  which  is  com- 
pletely fixed  in  the  fire;  it  suffers  no  change 
of  weight  appreciable  by  the  most  delicate 
balance,  when  exposed  to  a  white  heat,  and, 
therefore,  it  is  not  volatile.  Yet  its  solution 
in  water  cannot  be  evaporated  by  the  gen- 
tlest heat,  without  the  escape  of  a  sensible 
quantity  of  the  acid  with  the  steam.  Hence 
it  is  that  a  loss  is  always  experienced  in  the 
analysis  of  minerals  containing  this  acid, 
when  liquids  in  which  it  is  dissolved  are 
evaporated.  The  quantity  of  boracic  acid 
which  escapes  with  a  cubic  foot  of  steam, 
at  the  temperature  of  boiling  water,  cannot 
be  detected  by  our  most  sensible  re-agents ; 
and  nevertheless  the  many  hundred  tons 
annually  brought  from  Italy  as  an  article  of 
commerce,  are  procured  by  the  uninter- 
rupted accumulation  of  this  apparently  in- 
appreciable quantity.  The  hot  steam  which 
issues  from  the  interior  of  the  earth  is  al- 
lowed to  pass  through  cold  water  in  the 
lagoons  of  Castel  Nupva  and  Cherchiago ;  in 
this  way  the  boracic  acid  is  gradually  accu- 
mulated, till  at  last  it  may  be  obtained  in 
crystals  by  the  evaporation  of  the  water.  It 
is  evident,  from  the  temperature  of  the 
steam,  that  it  must  have  come  out  of  depths 
in  which  human  beings  and  animals  never 
could  have  lived,  and  yet  it  is  very  remarka- 
ble and  highly  important  that  ammonia  is 
never  absent  from  it.  In  the  large  works  in 
Liverpool,  where  natural  boracic  acid  is 
converted  into  borax,  many  hundred  pounds 
of  sulphate  of  ammonia  are  obtained  at  the 
same  time. 

This  ammonia  has  not  been  produced  by  the 
animal  organism,  it  existed  before  the  creation 
of  human  beings;  it  is  a  part,  a  primary 
constituent,  of  the  globe  itself. 

The  experiments  instituted  under  Lavoi- 
sier's guidance  by  the  Direction  des  Poudres 
et  Salpetres,  have  proved  that  during  the 
evaporation  of  the  saltpetre  ley,  the  salt 
volatilizes  with  the  water,  and  causes  a  loss 
which  could  not  before  be  explained.  It  is 
known  also,  that  in  sea  storms,  leaves  of 


mind,  which  would  penetrate  the  deepest  depths 
of  nature,  without  the  assistance  of  the  shaft  or 
ladder  of  the  miner.  This  is  poetry,  but  not  sober 
philosophical  inquiry. 


plants  in  trie  direction  of  the  wind  are 
covered  with  crystals  of  salt,  even  at  the 
distance  of  from  20  to  30  miles  from  the 
sea.  But  it  does  not  require  a  storm  to 
cause  the  volatilization  of  the  salt,  for  the 
air  hanging  over  the  sea  always  contains 
enough  of  this  substance  to  make  a  solution 
of  nitrate  of  silver  turbid,  and  every  breeze 
must  carry  this  away.  Now,  as  thousands 
of  tons  of  sea  water  annually  evaporate  into 
the  atmosphere,  a  corresponding  quantity 
of  the  salts  dissolved  in  it,  viz.  of  common 
salt,  chloride  of  potassium,  magnesia,  and 
the  remaining  constituents  of  the  sea  water, 
will  be  conveyed  by  wind  to  the  land. 

This  volatilization  is  a  source  of  con- 
siderable loss  in  salt  works,  especially  where 
the  proportion  of  salt  in  the  water  is  not 
large.  This  has  been  completely  proved  at 
the  salt  works  of  Nauheim,  by  the  very 
intelligent  director  of  that  establishment,  M. 
Wilhelmi.  He  hung  a  plate  of  glass  be- 
tween two  evaporating  houses,  which  were 
about  1200  paces  distant  from  each  other, 
and  found  in  the  morning,  after  the  drying 
of  the  dew,  that  the  glass  was  covered  with 
crystals  of  salt  on  one  or  the  other  side,  ac- 
cording to  the  direction  of  the  wind. 

By  the  continual  evaporation  of  the  sea, 
its  salts*  are  spread  over  the  whole  surface 
of  the  earth ;  and  being  subsequently  car- 
ried down  by  the  rain,  furnish  to  the  vegeta- 
tion those  salts  necessary  to  its  existence. 
This  is  the  origin  of  the  salts  found  in  the 
ashes  of  plants,  in  those  cases  where  the 
soil  could  not  have  yielded  them. 

In  a  comprehensive  view  of  the  phe- 
nomena of  nature,  we  have  no  scale  for 
that  which  we  are  accustomed  to  name, 
small  or  great;  all  our  ideas  are  proportioned 
to  what  we  see  around  us,  but  how  insig- 
nificant are  they  in  comparison  with  the 
whole  mass  of  the  globe!  that  which  is 
scarcely  observable  in  a  confined  district 
appears  inconceivably  large  when  regarded 
in  its  extension  through  unlimited  space 
The  atmosphere  contains  only  a  thousandth 
part  of  its  weight  of  carbonic  acid  ;  and  yel 
small  as  this  proportion  appears,  it  is  quite 


*  According  to  Marcet,  sea- water  contains  in 
1000  parts, 

26-660  Chloride  of  Sodium. 
4-660  Sulphate  of  Soda. 
T232  Chloride  of  Potassium. 
5'152  Chloride  of  Magnesium. 
0-153  Sulphate  of  Lime. 
According  to  M'Clemm,  the  water  of  the  North 
Sea  contains  in  1000  parts, 

24-84  Chloride  of  Sodium. 
2'42  Chloride  of  Magnesium. 
2'06  Sulphate  of  Magnesia. 
1'25  Chloride  of  Potassium. 
1-20  Sulphate  of  Lime. 

In  addition  to  these  constituents,  it  also  con- 
tains  inappreciable  quantities  of  carbonate  of  lime, 
magnesia,  iron,  manganese,  phosphate  of  lime, 
iodides  and  bromides,  silica,  sulphuretted  hy- 
drogen, and  organic  matter,  together  with  ain» 
monia  and  carbonic  acid.  (Liebig's  Annalen  der 
Chemie,  Bd.  xxxvii.  s.  3.) 


THE   ART   OF  CULTURE. 


43 


sufficient  to  supply  the  whole  of  the  present 
generation  of  living  beings  with  carbon  for 
a  thousand  years,  even  if  it  were  not  re- 
newed. Sea-water  contains  j^^^-y  of  its 
weight  of  carbonate  of  lime;  and  this  quan- 
tity, although  scarcely  appreciable  in  a 
pound,  is  the  source  from  which  myriads 
of  marine  mollusca  and  corals  are  supplied 
with  materials  for  their  habitations. 

Whilst  the  air  contains  only  from  4  to  6 
ten-thousandth  parts  of  its  volume  of  car- 
bonic acid,  sea-water  contains  100  times 
more,  (10,000  volumes  of  sea- water  contain 
620  volumes  of  carbonic  acid — Laurent, 
Bouillon,  Lagrange.)  Ammonia*  is  also 
found  in  this  water,  so  that  the  same  condi- 
tions which  sustain  living  beings  on  the  land 
are  combined  in  this  medium,  in  which  a 
whole  world  of  other  plants  and  animals 
exist. 

The  roots  of  plants  are  constantly  en- 
gaged in  collecting  from  the  rain  those 
alkalies  which  formed  part  of  the  sea- water, 
and  also  thoj;e  of  the  water  of  springs, 
which  penetrates  the  soil.  Without  alkalies 
and  alkaline  bases  most  plants  could  not 
exist,  and  without  plants  the  alkalies  would 
disappear  gradually  from  the  surface  of  the 
earth. 

When  it  is  considered,  that  sea-water  con- 
taius  less  than  one-millionth  of  its  own 
weight  of  iodine,  and  that  aU  combinations 
of  iodine  with  the  metallic  bases  of  alkalies 
are  highly  soluble  in  water,  some  provision 
must  necessarily  be  supposed  to  exist  in  the 
organization  of  sea-weed  and  the  different 
kinds  of  Fuci,  by  which  they  are  enabled 
'luring  their  life  to  extract  iodine  in  the 
form  of  ax  soluble  salt  from  sea-water,  and 
to  assimilate  it  in  such  a  manner,  that  it  is 
not  again  restored  to  the  surrounding  me- 
dium. These  plants  are  collectors  of  iodine, 
just  as  land  plants  are  of  alkalies ;  and  they 
yield  us  this  element,  in  quantities  such  as 
we  could  not  otherwise  obtain  from  the 
water  without  the  evaporation  of  whole 
seas. 

We  take  it  for  granted  that  the  sea-plants 
require  metallic  iodides  for  their  growth,  and 
that  their  existence  is  dependent  on  the 
presence  of  those  substances.  With  equal 
justice,  then,  we  conclude,  that  the  alkalies 
and  alkaline  earths,  always  found  in  the 
ashes  of  land-plants,  are  likewise  necessary 
for  their  developement. 


CHAPTER  VII. 

THE    ART    OF    CULTURE. 

THE  conditions  necessary  for  the  life  of 
all  vegetables  have  been  considered  in  the 


*  When  the  solid  saline  residue  obtained  by  the 
evaporation,  of  sea-water  is  heated  in  a  retort  to 
redness,  a  sublimate  of  sal-ammoniac  is  obtained. 
-MAKCET. 


preceding  part  of  the  work.  Carbonic  acid, 
ammonia,  and  water  yield  elements  for  all 
the  organs  of  plants.  Certain  inorganic 
substances — salts  and  metallic  oxides — serve 
peculiar  functions  in  their  organism,  ano 
many  of  them  must  be  viewed  as  essential 
constituents  of  particular  parts. 

The  atmosphere  and  the  soil  offer  the  same 
kind  of  nourishment  to  the  leaves  and  roots. 
The  former  contains  a  comparatively  inex- 
haustible supply  of  carbonic  acid  and  am- 
monia ;  the  latter,  by  means  of  its  humus, 
generates  constantly  fresh  carbonic  acid, 
whilst,  during  the  winter,  rain  and  snow  in- 
troduce into  the  soil  a  quantity  of  ammonia, 
sufficient  for  the  developement  of  the  leaves 
and  blossoms. 

The  complete,  or  it  may  be  said,  the  abso- 
lute insolubility  in  cold  water  of  vegetable 
matter  in  progress  of  decay,  (humus,)  ap- 
pears on  closer  consideration  to  be  a  most 
wise  arrangement  of  nature.  For  if  humus 
possessed  even  a  smaller  degree  of  solubility 
than  that  ascribed  to  the  substance  called  hu- 
mic  acid,  it  must  be  dissolved  by  rain-water. 
Thus,  the  yearly  irrigation  of  meadows, 
which  last  for  several  weeks,  would  remove 
a  great  part  of  it  from  the  ground,  and  a 
heavy  and  continued  rain  would  impoverish 
the  soil.  But  it  is  soluble  only  when  com- 
bined with  oxygen ;  it  can  be  taken  up  by 
water,  therefore,  only  as  carbonic  acid. 

When  kept  in  a  dry  place,  humus  may  be 
preserved  for  centuries;  but  when  moist- 
ened with  water,  it  converts  the  surrounding 
oxygen  into  carbonic  acid.  As  soon  as  the 
action  of  the  air  ceases,  that  is,  as  soon  as  it  is 
deprived  of  oxygen,  the  humus  suffers  no  far- 
ther change.  Its  decay  proceeds  only  when 
plants  grow  in  the  soil  containing  it ;  for 
they  absorb  by  their  roots  the  carbonic  acid 
as  it  is  formed.  The  soil  receives  again  from 
living  plants  the  carbonaceous  matter  it  thus 
loses,  so  that  the  proportion  of  humus  in  it 
does  not  decrease. 

The  stalactitic  caverns  in  Franconia,  and 
those  in  the  vicinity  of  Baireuth,  and  Streit- 
berg,  lie  beneath  a  fertile  arable  soil;  the 
abundant  decaying  vegetables  or  humus  in 
this  soil,  being  acted  on  by  moisture  and  air, 
constantly  evolve  carbonic  acid,  which  is  dis- 
solved by  the  rain.  The  rain-water  thus 
impregnated  permeates  the  porous  lime- 
stone, which  forms  the  walls  and  roofs  of 
the  caverns,  and  dissolves  in  its  passage  as 
much  carbonate  of  lime  as  corresponds  to 
the  quantity  of  carbonic  acid  contained  in  it. 
Water  and  the  excess  of  carbonic  acid  eva- 
porate from  this  solution  when  it  has  reached 
the  interior  of  the  caverns,  and  the  limestone 
is  deposited  on  the  walls  and  roofs  in  crys- 
talline crusts  of  various  forms.  There  are 
few  spots  on  the  earth  where  so  many  cir- 
cumstances favourable  to  the  production  of 
humate  of  lime  are  combined,  if  the  hurnua 
actually  existed  in  the  soil  in  the  form  of 
humic  acid.  Decaying  vegetable  matter, 
water,  and  lime  in  solution, "are  brought  to- 
gether, but  the  stalactites  formed  contain  no 


44 


AGRICULTURAL  CHEMISTRY. 


irace  of  vegetable  matter,  and  no  humic 
acid  ;  they  are  of  a  glistening  white  or  yel- 
lowish colour,  and  in  part  transparent,  like 
calcareous  spar,  and  may  be  heated  to  red- 
ness without  becoming  black. 

The  subterranean  vaults  in  the  old  castles 
near  the  Rhine,  the  if  Bergstrass,"  and 
Wetherau,  are  constructed  of  sandstone, 
granite,  or  basalt,  and  present  appearances 
similar  to  the  limestone  caverns.  The  roofs 
of  these  vaults  or  cellars  are  covered  exter- 
nally to  the  thickness  of  several  feet  with 
vegetable  mould,  which  has  been  formed  by 
the  decay  of  plants.  The  rain  falling  upon 
them  sinks  through  the  earth,  and  dissolves 
the  mortar  by  means  of  the  carbonic  acid 
derived  from  the  mould ;  and  this  solution 
evaporating  in  the  interior  of  the  vaults, 
covers  them  with  small  thin  stalactites, 
which  are  quite  free  from  humic  acid. 

In  such  a  filtering  apparatus,  built  by  the 
hand  of  nature,  we  have  placed  before  us  ex- 
periments which  have  been  continued  for  a 
hundred  or  thousand  years.  Now,  if  water 
possessed  the  power  of  dissolving  a  hun- 
dredth thousandth  part  of  its  own  weight  of 
humic  acid  or  humate  of  lime,  and  humic 
acid  were  present,  we  should  find  the  inner 
surface  of  the  roofs  of  these  vaults  and  cav- 
•erns  covered  with  these  substances ;  but  we 
cannot  detect  the  smallest  trace  of  them. 
There  could  scarcely  be  found  a  more  clear 
and  convincing  proof  of  the  absence  of  the 
humic  acid  of  chemists  in  common  vegeta- 
ble mould. 

The  common  view,  which  has  been 
adopted  respecting  the  modus  operandi  of 
humic  acid,  does  not  afford  any  explanation 
of  the  following  phenomenon : — A  very 
small  quantity  of  humic  acid  dissolved  in 
water  gives  it  a  yellow  or  brown  colour. 
Hence  it  would  be  supposed  that  a  soil 
would  be  more  fruitful  in  proportion  as  it 
was  capable  of  giving  this  colour  to  water, 
that  is,  of  yielding  it  humic  acid.  But  it  is 
very  remarkable  that  plants  do  not  thrive  in 
such  a  soil,  and  that  all  manure  must  have 
lost  this  property  before  it  can  exercise  a  fa- 
vourable influence  upon  their  vegetation. 
Water  from  barren  peat  soils  and  marshy 
meadows,  upon  which  few  plants  flourish, 
contains  much  of  this  humic  acid ;  but  all 
agriculturists  and  gardeners  agree  that  the 
most  suitable  and  best  manure  for  plants  is 
that  which  has  completely  lost  the  property 
of  giving  a  colour  to  water. 

The  soluble  substance,  which  gives  to 
water  a  brown  colour,  is  the  product  of  the 
putrefaction  of  all  animal  and  vegetable 
matter;  its  formation  is  an  evidence  that 
there  is  not  oxygen  sufficient  to  begin,  or  at 
least  to  complete  the  decay.  The  brown  so- 
lutions containing  this  substance  are  deco- 
lourised in  the  air  by  absorbing  oxygen,  and 
a  black  coaly  matter  precipitates — the  sub- 
stance named  "  coal  of  humus."  Now  if  a 
soil  were  impregnated  with  this  matter,  the 
effect  on  the  roots  of  plants  would  be  the 
same  as  that  of  entirely  depriving  the  soil  of 


oxygen ;  plants  would  be  as  little  able  to 
row  in  such  ground  as  they  would  if  ny- 
rated  protoxide  of  iron  were  mixed  with  the 
soil.  Indeed  some  barren  soils  have  been 
found  to  owe  their  fertility  to  this  very  caus*» 
The  sulphate  of  protoxide  of  iron  (coppe 
ras,)  which  forms  a  constituent  of  these  soils, 
possesses  a  powerful  affinity  for  oxygen, 
and  consequently  prevents  the  absorption  of 
that  gas  by  the  roots  of  plants  in  its  vicinity.* 
All  plants  die  in  soils  and  water  which  con- 
tain no  oxygen ;  absence  of  air  acts  exactly 
in  the  same  manner  as  an  excess  of  carbonic 
acid.  Stagnant  water  on  a  marshy  soil  ex- 
cludes air,  but  a  renewal  of  water  has  the 
same  effect  as  a  renewal  of  air,  because  wa- 
ter contains  it  in  solution.  If  the  water  is 
withdrawn  from  a  marsh,  free  access  s 
given  to  the  air,  and  the  marsh  is  change  i 
into  a  fruitful  meadow. 

In  a  soil  to  which  the  air  has  no  access, 
or  at  most  but  very  little,  the  remains  of  ani- 
mals and  vegetables  do  not  decay,  for  they 
can  only  do  so  when  freely  supplied  with 
oxygen;  but  they  undergo  putrefaction,  for 
which  air  is  present  in  sufficient  quantity. 
Putrefaction  is  known  to  be  a  most  powerfu-. 
deoxidising  process,  the  influence  of  which 
extends  to  all  surrounding  bodies,  even  ta 
the  roots  and  the  plants  themselves.  All 
substances  from  which  oxygen  can  be  ex- 
tracted yield  it  to  putrefying  bodies  ;  yellow 
oxide  of  iron  passes  into  the  state  of  black 
oxide,  sulphate  of  iron  into  sulphuret  of 
iron,  &,c. 

The  frequent  renewal  of  air  by  ploughing 
and  the  preparation  of  the  soil,  especially  iu> 
contact  with  alkaline  metallic  oxides,  the 
ashes  of  brown  coal,  burnt  lime  or  limestone, 
change  the  putrefaction  of  its  organic  con 
stituents  into  a  pure  process  of  oxidation ; 
and  from  the  moment  at  which  all  the  or- 
ganic matter  existing  in  a  soil  enters  into  a 
state  of  oxidation  or  decay,  its  fertility  is  in- 
creased. The  oxygen  is  no  longer  employed 
for  the  conversion  of  the  brown  soluble  mat- 
ter into  the  insoluble  coal  of  humus,  but 
serves  for  the  formation  of  carbonic  acid. 
This  change  takes  place  very  slowly,  and  in 
some  instances  the  oxygen  is  completely  ex- 
cluded by  it;  and  whenever  this  happens, 
the  soil  loses  its  fertility.  Thus,  in  the 
vicinity  of  Salzhausen  (a  village  in  Hesse 
Darmstadt,  famed  for  its  mineral  springs, 
upon  a  meadow  called  Griinschwalheimer, 
unfruitful  spots  are  seen  here  and  there 
covered  with  a  yellow  grass.  If  a  hole  be 
bored  from  twenty  to  twenty-five  feet  deep 
in  one  of  these  spots,  carbonic  acid  is  emit- 
ted from  it  with  such  violence  that  the  noise 
made  by  the  escape  of  the  gas  may  be  dis- 


*  The  most  obvious  method  of  removing  this 
salt  from  soils  in  which  it  may  be  contained  is  to 
manure  the  land  with  lime.  The  lime  unites  with 
the  sulphuric  acid  and  liberates  the  protoxide  of 
iron,  which  absorbs  oxygen  with  much  rapidity, 
and  is  converted  into  the  peroxide  of  iron.  This 
conversion  is  accelerated  by  giving  free  access  to 
the  air.  tiat  is,  oy  loosening  tbe  soil. 


THE   ART   OF   CULTURE. 


tmctly  heard  at  the  distance  of  several  feet. 
Here  the  carbonic  acid  rising  to  the  surface 
displaces  completely  all  the  air,  and  conse- 
quently all  the  oxygen,  from  the  soil;  and 
and  without  oxygen  neither  seeds  nor  roots 
can  be  developed;  a  plant  will  not  vegetate 
in  pure  nitrogen  or  carbonic  acid  gas. 

Humus  supplies  young  plants  with  nou- 
rishment by  the  roots,  until  their  leaves  are 
matured  sufficiently  to  act  as  exterior  organs 
of  nutrition;  its  quantity  heightens  the  fer- 
tility of  a  soil  by  yielding  more  nourishment 
in  this  first  pe'riod  of  growth,  and  conse- 
quently by  increasing  the  number  of  organs 
of  atmospheric  nutrition.  Those  plants 
which  receive  their  first  food  from  the  sub- 
stance of  their  seeds,  such  as  bulbous  plants, 
could  completely  dispense  with  humus ;  its 
presence  is  useful  only  in  so  far  as  it  in- 
creases and  accelerates  their  developement, 
but  it  is  not  necessary — indeed,  an  excess  of 
it  at  the  commencement  of  their  growth  is 
in  a  certain  measure  injurious. 

The  amount  of  food  which  young  plants 
can  take  from  the  atmosphere  in  the  form  of 
carbonic  acid  and  ammonia  is  limited ;  they 
cannot  assimilate  more  than  the  air  contains. 
Now,  if  the  quantity  of  their  stems,  leaves, 
and  branches  has  been  increased  by  the  ex- 
cess of  food  yielded  by  the  soil  at  the  com- 
mencement of  their  developement,  they  will 
require  for  the  completion  of  their  growth, 
and  for  the  formation  of  their  blossoms  and 
fruits,  more  nourishment  from  the  air  than 
it  can  afford,  and  consequently  they  will 
not  reach  maturity.  In  many  cases  the 
nourishment  afforded  by  the  air  under  these 
circumstances  suffices  only  to  complete  the 
formation  of  the  leaves,  stems,  and  branches. 
The  same  result  then  ensues  as  when  orna- 
mental plants  are  transplanted  from  the  pots 
in  which  they  have  grown  to  larger  ones, 
in  which  their  roots  are  permitted  to  increase 
and  multiply.  All  their  nourishment  is  em- 
ployed for  the  increase  of  their  roots  ami 
leaves;  they  spring,  as  it  is  said,  into  an 
herb  or  weed,  but  do  not  blossom.  When, 
on  the  contrary,  we  take  away  part  of  the 
branches,  and  of  course  their  leaves  with 
them,  from  dwarf  trees,  since  we  thus  pre- 
vent the  developement  of  new  branches,  an 
excess  of  nutriment  is  artificially  procured 
for  the  trees,  and  is  employed  by  them  in 
the  increase  of  the  blossoms  and  enlargement 
of  the  fruit.  It  is  to  effect  this  purpose  that 
vines  are  pruned. 

A  new  and  peculiar  process  of  vegetation 
ensues  in  all  perennial  plants,  such  as 
shrubs,  fruit  and  forest  trees,  after  the  com- 
plete maturity  of  their  fruit.  The  stem  of 
annual  plants  at  this  period  of  their  growth 
becomes  woody,  and  their  leaves  change  in 
colour.  The  leaves  of  trees  and  shrubs,  on 
the  contrary,  remain  in  activity  until  the  com- 
mencement of  the  winter.  The  formation 
of  the  layers  of  wood  progresses,  the  wood 
becomes  harder  and  more  solid,  but  after 
August  the  leaves  form  no  more  wood;  all 


the  carbonic  acid  which  the  plants  now  ab- 
sorb is  employed  for  the  production  of  nu- 
tritive matter  for  the  following  year  :  instead 
of  woody  fibre,  starch  is  formed,  and  is  dif- 
fused through  every  part  of  the  plant  by  the 
autumnal  sap  (seve  d'Aout.)*  According 
to  the  observations  of  M.  Heyer,  the  starch 
thus  deposited  in  the  body  of  the  tree  can  be 
recognised  in  its  known  form  by  the  aid  of  a 
good  microscope.  The  barks  of  several  as- 
pens and  pine-treesf  contain  so  much  of  this 
substance,  that  it  can  be  extracted  from  them 
as  from  potatoes  by  trituration  with  water.  It 
exists  also  in  the  roots  and  other  parts  of  pe- 
rennial plants.  A  very  early  winter,  or  sudden 
change  of  temperature,  prevents  the  forma- 
tion of  this  provision  for  the  following  year; 
the  wood,  as  in  the  case  of  the  vine-slock, 
does  not  ripen,  and  its  growth  is  in  the  next 
year  very  limited. 

From  the  starch  thus  accumulated,  sugar 
and  gum  are  produced  in  the  succeeding 
spring,  while  from  the  gum  those  constitu- 
ents of  the  leaves  and  young  sprouts  which 
contain  no  nitrogen  are  in  their  turn  formed. 
After  potatoes  have  germinated,  the  quantity 
of  starch  in  them  is  found  diminished.  The 
juice  of  the  maple-tree  ceases  to  be  sweet 
from  the  loss  of  its  sugar  when  its  buds, 
blossoms,  and  leaves  attain  their  maturity. 

The  branch  of  a  willow,  which  contains 
a  large  quantity  of  granules  of  starch  in 
every  part  of  its  woody  substance,  puts  forth 
both  roots  and  leaves  in  pure  distilled  rain- 
water; but  in  proportion  as  it  grows,  the 
starch  disappears,  it  being  evidently  ex- 
hausted for  the  formation  of  the  roots  and 
leaves.  In  the  course  of  these  experiments, 
M.  Heyer  made  the  interesting  observation, 
that  such  branches  when  placed  in  snow 
water  (which  contains  ammonia)  produced 
roots  three  or  four  times  longer  than  those 
which  they  formed  in  pure  distilled  water, 
and  that  this  pure  water  remained  clear, 
while  the  rain-water  gradually  acquired  a 
yellow  colour. 

Upon  the  blossoming  of  the  sugar-cane, 
likewise,  part  of  the  sugar  disappears ;  and 
it  has  been  ascertained,  that  the  sugar  does 
not  accumulate  in  the  beet-root  until  after 
the  leaves  are  completely  formed. 

Much  attention  has  recently  been  drawn 
to  the  fact  that  the  produce  of  potatoes  may 
be  much  increased  by  plucking  off  the  blos- 
soms from  the  plants  producing  them,  a 
result  quite  consistent  with  theory  This 
important  observation  has  been  completely 
confirmed  by  M.  Zeller,  the  director  of  the 
Agricultural  Society  at  Darmstadt.  In  the 
year  1839,  two  fields  of  the  same  size,  lying 
side  by  side  and  manured  in  the  same  man- 
ner, were  planted  with  potatoes.  When  the 
plants  had  flowered,  the  blossoms  were  re- 


*  Hartig,  in  Erdmann  und  Schweigger-Seidels 
Journal,  V.  217.  1335. 

T  It  is  well  known  that  bread  is  made  from  the 
bark  of  pines  in  Sweden  during  famines. 


AGRICULTURAL   CHEMISTRY. 


moved  from  those  in  one  field,  while  those 
in  the  other  field  were  left  untouched.  The 
former  produced  47  bolls,  the  latter  only  37 
bolls. 

These  well-authenticated  observations  re- 
move every  doubt  as  to  the  part  which  sugar, 
starch,  and  gum  play  in  the  developement  of 
plants;  and  it  ceases  to  be  enigmatical,  why 
these  three  substances  exercise  no  influence 
on  the  growth  or  process  of  nutrition  of  a 
matured  plant,  when  supplied  to  them  as 
food. 

The  accumulation  of  starch  in  plants 
during  the  autumn  has  been  compared,  al- 
though certainly  erroneously,  to  the  fatten- 
ing ot  hibernating  animals  before  their  winter 
sleep;  but  in  these  animals  every  vital  func- 
tion, except  the  process  of  respiration,  is 
suspended,  and  they  only  require,  like  a 
lamp  slowly  burning,  a  substance  rich  in 
carbon  and  hydrogen  to  support  the  pro- 
cess of  combustion  in  the  lungs.  On  their 
awaking  from  their  torpor  in  the  spring,  the 
fat  has  disappeared,  but  has  not  served  as 
nourishment.  It  has  not  caused  the  least 
increase  in  any  part  of  their  body,  neither 
has  it  changed  the  quality  of  any  of  their 
organs.  With  nutrition,  properly  so  called, 
the  fat  in  these  animals  has  not  the  least 
connexion. 

The  annual  plants  form  and  collect  their 
future  nourishment  in  the  same  way  as  the 
perennial ;  they  store  it  in  their  seeds  in  the 
form  of  vegetable  albumen,  starch  and  gum, 
which  are  used  by  the  germs  for  the  forma- 
tion of  their  leaves  and  first  radicle  fibres. 
The  proper  nutrition  of  the  plants,  their  in- 
crease in  size,  begins  after  these  organs  are 
formed. 

Every  germ  and  every  bud  of  a  perennial 
plant  is  the  engrafted  embryo  of  a  new  indi- 
vidual, while  the  nutriment  accumulated  in 
the  stem  and  roots,  corresponds  to  the  albu- 
men of  the  seeds. 

Nutritive  matters  are,  correctly  speaking, 
those  substances  which,  when  presented 
from  without,  are  capable  of  sustaining  the 
life  and  all  the  functions  of  an  organism,  by 
furnishing  to  the  different  parts  of  plants  the 
materials  for  the  production  of  their  peculiar 
constituents. 

In  animals,  the  blood  is  the  source  of  the 
material  of  the  muscles  and  nerves;  by  one 
of  its  component  parts,  the  blood  supports 
the  process  of  respiration,  by  others,  the 
peculiar  vital  functions;  every  part  of  the 
body  is  supplied  with  nourishment  by  it, 
but  its  own  production  is  a  special  function, 
without  which  we  could  not  conceive  life 
to  continue.  If  we  destroy  the  activity  of 
the  organs  which  produce  it,  or  if  we  inject 
the  blood  of  one  animal  into  the  veins  of 
another,  at  all  events,  if  we  carry  this  be- 
yond certain  limits,  death  is  the  consequence. 

If  we  could  introduce  into  a  tree  woody 
fibre  in  a  state  of  solution,  it  would  be  the 
same  thing  as  placing  a  potato  plant  to 
vegetate  in  a  paste  of  starch.  The  office  of 


the  leaves  is  to  form  starch,  woody  fiore, 
and  sugar ;  consequently,  if  we  convey  these 
substances  through  the  roots,  the  vital  func 
tions  of  the  leaves  must  cease,  and  if  the 
process  of  assimilation  cannot  take  anothe* 
form,  the  plant  must  die. 

Other  substances  must  be  present  in  a 
plant,  besides  the  starch,  sugar  and  gum,  if 
these  are  to  take  part  in  the  developement 
of  the  germ,  leaves,  and  first  radicle  fibres. 
There  is  no  doubt  that  a  grain  of  wheat  con- 
tains within  itself  the  component  parts  of 
the  germ  and  of  the  radicle  fibres,  and,  we 
must  suppose,  exactly  in  the  proportion  ne- 
cessary for  their  formation.  These  compo- 
nent parts  are  starch  and  gluten;  and  it  is 
evident  that  neither  of  them  alone,  but  ihat 
both  simultaneously  assist  in  the  formation 
of  the  root,  for  they  both  suffer  changes 
under  the  action  of  air,  moisture,  and  a  suit 
able  temperature.  'The  starch  is  convertel 
into  sugar,  and  the  gluten  also  assumes  a 
new  form,  and  both  acquire  the  capability  of" 
being  dissolved  in  water,  and  of  thus  being 
conveyed  to  every  part  of  the  plant.  Both 
the  starch  and  the  gum  are  completely  con- 
sumed in  the  formation  of  the  first  part  of 
the  roots  and  leaves;  and  excess  of  either 
could  not  be  used  in  the  formation  of  leaves, 
or  in  any  other  way. 

The  conversion  of  starch  into  sugar  during 
the  germination  of  grain  is  ascribed  to  a 
vegetable  principle  called  diastase,  which  is 
generated  during  the  act  of  commencing 
germination.  But  this  mode  of  transforma- 
tion can  also  be  effected  by  gluten,  although 
it  requires  a  longer  time.  Seeds,  which  have 
germinated,  always  contain  much  more  dias- 
tase than  is  necessary  for  the  conversion  of 
their  starch  into  sugar,  for  five  parts  by  weight 
of  starch  can  be  converted  into  sugar  by  one 
part  of  malted  barley.  This  excess  of  diastase 
can  by  no  means  be  regarded  as  accidental, 
for,  like  the  starch,  it  aids  in  the  formation 
of  the  first  organs  of  the  young  plant,  and 
disappears  with  the  sugar;  diastase  contains 
nitrogen  and  furnishes  the  elements  of  ve- 
getable albumen. 

Carbonic  acid,  water,  and  ammonia,  are 
the  food  of  fully-developed  plants ;  starch, 
sugar,  and  gum,  serve,  when  accompanied 
by  an  azotised  substance,  to  sustain  the  em- 
bryo, until  its  first  organs  of  nutrition  are 
unfolded.  The  nutrition  of  a  foetus  and  de- 
velopement of  an  egg  proceed  in  a  totally 
different  manner  from  that  of  an  animal 
which  is  separated  from  its  parent ;  the  ex- 
clusion of  air  does  not  endanger  the  life  of 
the  foetus,  but  would  certainly  cause  the 
death  of  the  independent  animal.  In  the 
same  manner,  pure  water  is  more  advan- 
tageous to  the  growth  of  a  young  plant, 
than  that  containing  carbonic  acid,  but  after 
a  month  the  reverse  is  the  case. 

The  formation  of  sugar  in  maple-trees 
does  not  take  place  in  the  roots,  but  in  the 
woody  substance  of  the  stem.  The  quantity 
of  sugar  in  the  sap  augments  until  it  reaches 


THE   ART  OF  CULTURE. 


a  certain  height  in  the  stem  of  the  plant, 
above  which  point  it  remains  stationary. 

Just  as  germinating  barley  produces  a 
substance  which,  in  contact  with  starch, 
causes  it  to  lose  its  insolubility  and  to  be- 
come sugar,  so  in  the  roots  of  the  maple,  at 
the  commencement  of  vegetation,  a  sub- 
stance must  be  formed,  which,  being  dis- 
solved in  water,  permeates  the  wood  of  the 
trunk,  and  converts  into  sugar  the  starch,  or 
whatever  it  may  be,  which  it  finds  deposited 
there.  It  is  certain,  that  when  a  hole  is 
bored  into  the  trunk  of  a  maple-tree  just 
above  its  roots,  filled  with  sugar,  and  then 
closed  again,  the  sugar  is  dissolved  by  the 
ascending  sap.  It  is  further  possible  that 
this  sugar  may  be  disposed  of  in  the  same 
manner  as  that  formed  in  the  trunks;  at  all 
events  it  is  certain,  that  the  introduction  of 
it  does  not  prevent  the  action  of  the  juice 
upon  the  starch,  and  since  the  quantity  of 
the  sugar  present  is  now  greater  than  can 
be  exhausted  by  the  leaves  and  buds,  it  is 
excreted  from  the  surface  of  the  leaves  or 
bark.  (Certain  diseases  of  trees,  for  example 
that  called  honey-dew,  evidently  depend  on 
the  want  of  the  due  proportion  between  the 
quantity  of  the  azotised  and  that  of  the  un- 
azotised  substances  which  are  applied  to 
them  as  nutriment. 

In  whatever  form,  therefore,  we  supply 
plants  with  those  substances  which  are  the 
products  of  their  own  action,  in  no  instance 
do  they  appear  to  have  any  effect  upon  their 
growth,  or  to  replace  what  they  have  lost. 
Sugar,  gum,  and  starch,  are  not  food  for 
plants,  and  the  same  must  be  said  of  humic 
acid,  which  is  so  closely  allied  to  them  in 
composition. 

If  now  we  direct  our  attention  to  the  par- 
ticular organs  of  a  plant,  we  find  every  fibre 
and  every  particle  of  wood  surrounded  by  a 
juice  containing  an  azotised  matter;  while 
the  starch,  granules,  and  sugar  are  enclosed 
in  cells  formed  of  a  substance  containing  ni- 
trogen. Indeed  every  where,  in  all  the  juices 
of  the  fruits  and  blossoms,  we  find  a  sub- 
stance destitute  of  nitrogen,  accompanied 
by  one  which  contains  that  element. 

The  wood  of  the  stem  cannot  be  formed, 
quasi  wood,  in  the  leaves,  but  another  sub- 
stance must  be  produced  which  is  capable 
of  being  transformed  into  wood.  This  sub- 
stance must  be  in  a  state  of  solution,  and 
accompanied  by  a  compound  containing  ni- 
trogen; it  is  very  probable  that  the  wood 
and  the  vegetable  gluten,  the  starch  granules 
and  the  cells  containing  them,  are  formed 
simultaneously,  and  in  this  case  a  certain 
fixed  proportion  between  them  would  be  a 
condition  necessary  for  their  production. 

According  to  this  view,  the  assimilation 
of  the  substances  generated  in  the  leaves 
will  (cceteris  paribus)  depend  on  the  quan- 
tity of  nitrogen  contained  in  the  food.  When 
a  sufficient  quantity  of  nitrogen  is  not  pre- 
sent to  aid  in  the  assimilation  of  the  sub- 
stances which  do  not  contain  it,  these  sub- 
itances  will  be  separated  as  excrements  from 


the  bark,  roots,  leaves,  and  branches.  The 
exudations  of  mannite,  gum,  and  sugar,  in 
strong  and  healthy  plants  cannot  be  ascribed 
to  any  other  cause.* 

Analogous  phenomena  are  presented  by 
the  process  of  digestion  in  the  human  or- 
ganism. In  order  that  the  loss  which  every 
part  of  the  body  sustains  by  the  processes 
of  respiration  and  perspiration  may  be  re- 
stored to  it,  the  organs  of  digestion  require 
to  be  supplied  with  food,  consisting  of  sub- 
stances containing  nitrogen,  and  of  others 
destitute  of  it,  in  definite  proportions.  If 
the  substances  which  do  not  contain  nitrogen 
preponderate,  either  they  will  be  expended 
in  the  formation  of  fat,  or  they  will  pass 
unchanged  through  the  organism.  This  is 
particularly  observed  in  those  people  who 
live  almost  exclusively  upon  potatoes ;  their 
excrements  contain  a  large  quantity  of  un- 
changed granules  of  starch,  of  which  no 
trace  can  be  detected  when  gluten  or  flesh 
is  taken  in  proper  proportions,  because  in 
this  case  the  starch  has  been  rendered  capa- 
ble of  assimilation.  Potatoes,  which  when 
mixed  with  hay  alone  are  scarcely  capable 
of  supporting  the  strength  of  a  horse,  form 
with  bread  and  oats  a  strong  and  wholesome 
fodder. 

It  will  be  evident  from  the  preceding  con- 
siderations, that  the  products  generated  by 
a  plant  may  vary  exceedingly,  according  to 
the  substances  given  it  as  food.  A  super- 
abundance of  carbon  in  the  state  of  carbonic 
acid  conveyed  through  the  roots  of  plants, 
without  being  accompanied  by  nitrogen, 
cannot  be  converted  either  into  gluten,  al- 
bumen, wood,  or  any  other  component  part 
of  an  organ  ;  but  either  it  will  be  separated 
in  the  form  of  excrements,  such  as  sugar, 
starch,  oil,  wax,  resin,  mannite,  or  gum,  or 
these  substances  will  be  deposited  in  greater 
or  less  quantity  in  the  wide  cells  and  vessels. 

The  quantity  of  gluten,  vegetable  albu- 
men, and  mucilage,  will  augment  when 
plants  are  supplied  with  an  excess  of  food 
containing  nitrogen ;  and  amrnoniacal  salts 
will  remain  in  the  sap,  when,  for  example, 
in  the  culture  of  the  beet,  we  manure  the 
soil  with  a  highly  nitrogenous  substance,  or 
when  we  suppress  the  functions  of  the  leaves 
by  removing  them  from  the  plant. 

We  know  that  the  ananas  is  scarcely 
eatable  in  its  wild  state,  and  that  it  shoots 
forth  a  great  quantity  of  leaves  when  treated 
with  rich  animal  manure,  without  the  fruit 
on  that  account  acquiring  a  large  amount 
of  sugar;  that  the  quantity  of  starch  in  po- 
tatoes increases  when  the  soil  contains  much 
humus,  but  decreases  when  the  soil  is  ma- 


*  M.  Trapp,  in  Giessen,  possesses  a  Cleroden- 
dronfragrans,  which  grows  in  the  house,  and  ex- 
udes on  the  surface  of  its  leaves  in  September 
large  colourless  drops  of  sugar-candy,  which  form 
regular  crystals  upon  drying ; — I  am  not  aware 
whether  the  juice  of  this  plant  contains  sugar. 
Professor  Redtenbacher,  of  Prague,  informs  me 
that  he  has  analysed  the  crystals,  and  found  them 
to  be  perfectly  pure  sugar. — ED. 


4S 


AGRICULTURAL    CHEMISTRY. 


nured  with  strong  animal  manure,  although 
then  the  number  of  cells  increases,  the  po- 
tatoes acquiring  in  the  first  case  a  mealy,  in 
the  second  a  soapy,  consistence.  Beet-roots, 
taken  from  a  barren,  sandy  soil,  contain  a 
maximum  of  sugar,  and  no  arnmoniacal 
salts;  and  the  Teltowa  parsnep  loses  its 
mealy  state  in  a  manured  land,  because  there 
all  the  circumstances  necessary  for  the  for- 
mation of  cells  are  united.* 

An  abnormal  production  of  certain  com- 
ponent parts  of  plants  presupposes  a  power 
and  capability  of  assimilation  to  which  the 
most  powerful  chemical  action  cannot  be 
compared.  The  best  idea  of  it  may  be 
formed  by  considering  that  it  surpasses  in 
power  the  strongest  galvanic  battery,  with 
which  we  are  not  able  to  separate  the  oxy- 
gen from  carbonic  acid.  The  affinity  of 
chlorine  for  hydrogen,  and  its  power  to  de- 
compose vnater  under  the  influence  of  light 
and  set  at  liberty  its  oxygen,  cannot  be  con- 
sidered as  at  all  equalling  the  power  and 
energy  with  which  a  leaf  separated  from  a 
plant  decomposes  the  carbonic  acid  which 
it  absorbs. 

•  The  common  opinion,  that  only  the  direct 
solar  rays  can  effect  the  decomposition  of 
carbonic  acid  in  the  leaves  of  plants,  and 
that  reflected  or  diffused  light  does  not  pos- 
sess this  property,  is  wholly  an  error,  for 
exactly  the  same  constituents  are  generated 
in  a  number  of  plants,  whether  the  direct 
rays  of  the  sun  fall  upon  them,  or  whether 
they  grow  in  the  shade.  They  require  light, 
and  indeed  sun-light,  but  it  is  not  necessary 
that  the  direct  rays  of  the  sun  reach  them. 
Their  functions  certainly  proceed  with 
greater  intensity  and  rapidity  in  sunshine 
than  in  the  diffused  light  of  day;  but  there 
is  nothing  more  in  this  than  the  similar 
action  which  light  exercises  on  ordinary 
chemical  combinations;  it  merely  accelerates 
in  a  greater  or  less  degree  the  action  already 
subsisting. 

Thus  chlorine  and  hydrogen  combining 
form  muriatic  acid.  This  combination  is 
effected  in  a  few  hours  in  common  daylight, 
but  it  ensues  instantly,  with  a  violent  ex- 
plosion, under  exposure  to  the  direct  solar 
rays,  whilst  not  the  slightest  change  in  the 
two  gases  takes  place  in  perfect  darkness. 
When  the  liquid  hydrocarburet  of  chlorine, 
resulting  from  the  union  of  the  olefiant  gas 
of  the  associated  Dutch  chemists  with  chlo- 
rine, is  exposed  in  a  vessel  with  chlorine 
gas  to  the  direct  solar  rays,  chloride  of  car- 
bon is  immediately  produced  ;  but  the  same 
compound  can  be  obtained  with  equal  faci- 
lity in  the  diffused  light  of  day,  a  longer  time 
only  being  required.  When  this  experiment 
is  performed  in  the  way  first  mentioned,  two 


*  Children  fed  upon  arrow-root,  salep,  or  in- 
deed any  kind  of  amylaceous  food,  which  does 
not  contain  ingredients  fined  for  the  formation  of 
bones  and  muscles,  become  fat,  and  acquire  much 
embonpoint ;  their  limbs  appear  full,  but  they  do 
not  acquire  strength,  nor  are  their  organs  pro- 
perly developed. 


'products  only  are  observed  (muri&Mc  acid 
land  perchloride  of  carbon);  whilst  by  the 
j  latter  method  a  class  of  intermediate  bodies 
I  are  produced,  in  which  the  quantity  of  chlo- 
rine constantly  augments,  until  at  last  the 
whoie  liquid  hydrocarburet  of  chlorine  is 
converted  into  the  same  two  products  as  in 
the  first  case.  Here,  also,  not  the  slightest 
trace  of  decomposition  takes  place  in  the 
dark.  Nitric  acid  is  decomposed  in  common 
daylight  into  oxygen,  and  peroxide  of  nitro- 
gen ;  and  chloride  of  silver  becomes  black 
in  the  diffused  light  of  day,  as  well  as  in  the 
direct  solar  rays ; — in  short,  all  actions  of  a 
similar  kind  proceed  in  the  same  way  in  dif- 
fused light  as  well  as  in  the  solar  light,  the 
only  difference  consisting  in  the  time  in 
which  they  are  effected.  It  cannot  be  other- 
wise in  plants,  for  the  mode  of  their  nutri- 
ment is  the  same  in  all,  and  their  component 
substances  afford  proof  that  their  food  has 
suffered  absolutely  the  same  change,  whether 
they  grow  in  the  sunshine  or  in  the  shade. 

All  the  carbonic  acid,  therefore,  which 
we  supply  to  a  plant  will  undergo  a  trans- 
formation, provided  its  quantity  be  not 
greater  than  can  be  decomposed  by  the 
leaves.  We  know  that  an  excess  of  car- 
bonic acid  kills  plants,  but  we  know  also 
that  nitrogen  to  a  certain  degree  is  not  essen- 
tial for  the  decomposition  of  carbonic  acid. 
All  the  experiments  hitherto  instituted  prove, 
that  fresh  leaves  placed  in  water  impregnated 
with  carbonic  acid,  and  exposed  to  the  in- 
fluence of  solar  light,  emit  oxygen  gas, 
whilst  the  carbonic  acid  disappears.  Now 
in  these  experiments  no  nitrogen  is  supplied 
at  the  same  time  with  the  carbonic  acid ; 
hence  no  other  conclusion  can  be  drawn 
from  them  than  that  nitrogen  is  not  neces- 
sary for  the  decomposition  of  carbonic  acid, 
— for  the  exercise,  therefore,  of  one  of  the 
functions  of  plants.  And  yet  the  presence 
of  a  substance  containing  this  element  ap- 
pears to  be  indispensable  for  the  assimilation 
of  the  products  newly  formed  by  the  decom- 
position of  the  carbonic  acid,  and  their  con- 
sequent adaptation  for  entering  into  the 
composition  of  the  different  organs. 

The  carbon  abstracted  from  the  carbonic 
acid  acquires  in  the  leaves  a  new  form,  in 
which  it  is  soluble  and  transferable  to  all 
parts  of  the  plant.  In  this  new  form  the 
carbon  aids  in  constituting  several  new  pro- 
ducts ;  these  are  named  sugar  when  they 
possess  a  sweet  taste,  gum  or  mucilage 
when  tasteless,  and  excrementitious  matters 
when  expelled  by  the  roots. 

Hence  it  is  evident  that  the  quantity  and 
quality  of  the  substances  generated  by  the 
vital  processes  of  a  plant  will  vary  accord- 
ing to  the  proportion  of  the  different  kinds 
of  food  with  which  it  is  supplied.  The  de- 
velopement  of  every  part  of  a  plant  in  a 
free  and  uncultivated  state  depends  on  me 
amount  and  nature  of  the  food  afforded  to  it 
by  the  spot  on  which  it  grows.  A  plant  is 
developed  on  the  most  sterile  and  unfruitful 
soil  as  well  as  on  the  most  luxuriant  and 


THE   ART   OF   CULTURE. 


49 


fertile,  the  only  difference  which  can  be  ob- 
served being  in  its  height  and  size,  in  the 
number  of  its  twigs,  branches,  leaves,  blos- 
soms, and  fruit.  Whilst  the  individual  or- 
gans of  a  plant  increase  on  a  fertile  soil, 
they  diminish  on  another  where  those  sub- 
stances which  are  necessary  for  their  forma- 
tion are  not  so  bountifully  supplied ;  and 
the  proportion  of  the  constituents  which 
contain  nitrogen  and  of  those  which  do  not 
in  plants  varies  with  the  amount  of  nitro- 
genous matters  in  their  food. 

The  developement  of  the  stem,  leaves, 
blossoms,  and  fruit  of  plants  is  dependent  on 
certain  conditions,  the  knowledge  of  which 
enables  us  to  exercise  some  influence  on 
their  internal  constituents  as  well  as  on  their 
size.  It  is  the  duty  of  the  natural  philoso- 
pher to  discover  what  these  conditions  are ; 
for  the  fundamental  principles  of  agriculture 
must  be  based  on  a  knowledge  of  them. 
There  is  no  profession  which  can  be  com- 
pared in  importance  with  that  of  agricul- 
ture, for  to  it  belongs  the  production  of  food 
for  man  and  animals ;  on  it  depends  the 
welfare  and  developement  of  the  whole 
human  species,  the  riches  of  states,  and  all 
commerce.  There  is  no  other  profession  in 
which  the  application  of  correct  principles 
is  productive  of  more  beneficial  effects,  or  is 
of  greater  and  more  decided  influence. 
Hence  it  appears  quite  unaccountable,  that 
we  may  vainly  search  for  one  leading  prin- 
ciple in  the  writings  of  agriculturists  and 
vegetable  physiologists. 

The  methods  employed  in  the  cultivation 
of  land  are  different  in  every  country,  and 
in  every  district ;  and  when  we  inquire  the 
causes  of  these  differences,  we  receive  the 
answer,  that  they  depend  upon  circum- 
stances. (Les  circonstances  font  les  assole 
ments.)  No  answer  could  show  ignorance 
more  plainly,  since  no  one  has  ever  yet  de- 
voted himself  to  ascertain  what  these  cir- 
cumstances are.  Thus  also  when  we  inquire 
in  what  manner  manure  acts,  we  are  an- 
swered by  the  most  intelligent  men,  that  its 
action  is  covered  by  the  veil  of  Isis  j  and 
when  we  demand  further  what  this  means, 
we  discover  merely  that  the  excrements  of 
men  and  animals  are  supposed  to  contain 
an  incomprehensible  something  which  assists 
in  the  nutrition  of  plants,  and  increases  their 
size.  This  opinion  is  embraced  without 
even  an  attempt  being  made  to  discover  the 
component  parts  of  manure,  or  to  become 
acquainted  with  its  nature. 

In  addition  to  the  general  conditions,  such 
as  heat,  light,  moisture,  and  the  component 
parts  of  the  atmosphere,  which  are  neces- 
sary for  the  growth  of  all  plants,  certain 
substances  are  found  to  exercise  a  peculiar 
influence  on  the  developement  of  particular 
families.  These  substances  either  are  al- 
ready contained  in  the  soil,  or  are  supplied 
to  it  in  the  form  of  the  matters  known  under 
the  general  name  of  manure.  But  what 
does  the  soil  contain,  and  what  are  the  com- 
ponents of  tne  substances  used  as  .manure?  | 
7 


Until  these  points  are  satisfactorily  deter- 
mined, a  rational  system  of  agriculture  can- 
not exist.  The  power  and  knowledge  of  the 
physiologist,  of  the  agriculturist  and  chemist, 
must  be  united  for  the  complete  solution  of 
these  questions ;  and  in  order  to  attain  this 
end,  a  commencement  must  be  made. 

The  general  object  of  agriculture  is  to 
produce  in  the  most  advantageous  manner 
certain  qualities,  or  a  maximum  size,  in 
certain  parts  or  organs  of  particular  plants 
Now,  this  object  can  be  attained  only  by  the 
application  of  those  substances  which  we 
know  to  be  indispensable  to  the  developement 
of  these  parts  or  organs,  or  by  supplying  the 
conditions  necessary  to  the  production  of  the 
qualities  desired. 

The  rules  of  a  rational  system  of  agricul- 
ture should  enable  us,  therefore,  to  give  to 
each  plant  that  which  it  requires  for  the  at- 
tainment of  the  object  in  view. 

The  special  object  of  agriculture  is  to  ob- 
tain an  abnormal  developement  and  produc- 
tion of  certain  parts  of  plants,  or  of  certain 
vegetable  matters,  which  are  employed  as 
food  for  man  and  animals,  or  for  the  pur- 
pose of  industry. 

The  means  employed  for  effecting  these 
two  purposes  are  very  different.  Thus  the 
mode  of  culture,  employed  for  the  purpose 
of  procuring  fine  pliable  straw  for  Floren- 
tine hats,  is  the  very  opposite  to  that  which 
must  be  adopted  in  order  to  produce  a  maxi- 
mum of  corn  from  the  same  plant.  Peculiai 
methods  must  be  used  for  the  production  oi 
nitrogen  in  the  seeds,  others  for  giving 
strength  and  solidity  to  the  straw,  and  others 
again  must  be  followed  when  we  wish  to 
give  such  strength  and  solidity  to  the  straw 
as  will  enable  it  to  bear  the  weight  of  the 
ears. 

We  must  proceed  in  the  culture  of  plants 
in  precisely  the  same  manner  as  we  do  in 
the  fattening  of  animals.  The  flesh  of  the 
stag  and  roe,  or  of  wild  animals  in  general, 
is  quite  devoid  of  fat,  like  the  muscular  flesh 
of  the  Arab ;  or  it  contains  only  small  quan- 
tities of  it.  The  production  of  flesh  and  fat 
may  be  artificially  increased;  all  domestic 
animals,  for  example,  contain  much  fat. 
We  give  food  to  animals,  which  increases 
the  activity  of  certain  organs,  and  is  itself 
capable  of  being  transformed  into  fat.  We 
add  to  the  quantity  of  food,  or  we  lessen  the 
processes  of  respiration  and  perspiration  by 
preventing  motion.  The  conditions  neces- 
sary to  effect  this  purpose  in  birds  are  dif- 
ferent from  those  in  quadrupeds ;  and  it  is 
well  known  that  charcoal  powder  producer* 
such  an  excessive  growth  of  the  liver  of  a 
goose,  as  at  length  causes  the  death  of  the 
animal. 

The  increase  or  diminution  of  the  vital 
activity  of  vegetables  depends  only  on  heat 
and  solar  light,  which  we  have  not  arbitra- 
rily at  our  disposal :  all  that  we  can  do  is  to 
supply  those  substances  which  are  adapted 
for  assimilation  by  the  power  already  pre- 
sent in  the  organs  of  the  plant.  But  wha 


50 


AGRICULTURAL    CHEMISTRY". 


then  are  these  substances?  They  may 
easily  be  detected  by  the  examination  of  a 
soil,  which  is  always^  fertile  in  given  cosmi- 
cal  and  atmospheric  conditions;  for  it  is 
evident,  that  the  knowledge  of  its  state  and 
composition  must  enable  us  to  discover  the 
circumstances  under  which  a  sterile  soil 
may  be  rendered  fertile.  It  is  the  duty  of 
the  chemist  to  explain  the  composition  of  a 
fertile  soil,,  but  the  discovery  of  its  proper 
state  or  condition  belongs  to  the  agricultu- 
rist ;  our  present  business  lies  only  with  the 
former. 

Arable  land  is  originally  formed  by  the 
crumbling  of  rocks,  and  its  properties  de- 
pend on  the  nature  of  their  principal  com- 
ponent parts.  Sand,  clay,  and  lime,  are  the 
names  given  to  the  principal  constituents  of 
the  different  kinds  of  soil/ 

Pure  sand  and  pure  limestones,  in  which 
there  are  no  other  inorganic  substances  ex- 
cept siliceous  earth,  carbonate  or  silicate  of 
lime,  form  absolutely  barren  soils.  But  ar- 
gillaceous earths  form  always  a  part  of  fer- 
tile soils.  Now  from  whence  come  the 
argillaceous  earths  in  arable  land,  what  are 
their  constituents,  and  what  part  do  they 
play  in  favouring  vegetation?  They  are 
produced  by  the  disintegration  of  aluminous 
minerals  by  the  action  of  the  weather ;  the 
common  potash  and  soda  felspars,  Labrador 
spar,  mica,  and  the  zeolites,  are  the  most 
common  aluminous  earths,  which  undergo 
this  change.  These  minerals  are  found 
mixed  with  other  substances  in  granite, 
gneiss,  mica-slate,  porphyry,  clay-slate, 
grauwacke,  and  the  volcanic  rocks,  basalt, 
clinkstone,  and  lava.  In  the  grauwacke, 
we  have  pure  quartz,  clay-slate,  and  lime  ; 
in  the  sandstones,  quartz  and  loam.  The 
transition  limestone  and  the  dolomites  con- 
tain an  intermixture  of  clay,  felspar,  por- 
phyry, and  clay-slate;  and  the  mountain 
limestone  is  remarkable  for  the  quantity  of 
argillaceous  earths  which  it  contains.  Jura 
limestone  contains  3 — 20,  that  of  the  Wur- 
temberg  Alps  45 — 50  per  cent,  of  these 
earths.  And  in  the  muschelkalk  and  the 
calcaire  grossier  they  exist  in  greater  or  less 
quantity. 

It  is  known,  that  the  aluminous  minerals 
are  the  most  widely  diffused  on  the  surface 
of  the  earth,  and  as  we  have  already  men- 
tioned, all  fertile  soils,  or  soils  capable  of 
culture,  contain  alumina  as  an  invariable 
constituent.  There  must,  therefore,  be 
something  in  aluminous  earth  which  ena- 
bles it  to  exercise  an  influence  on  the  life  of 
plants,  srd  to  assist  in  their  developement. 
The  p;rrvwerty  on  whica  this  depends  is  that 
of  its  invariably  containing  potash  and  soda. 

Alumina  exercises  only  an  indirect  influ- 
ence on  vegetation,  by  its  power  of  attract- 
ing and  retaining  water  and  ammonia;  it  is 
itself  very  rarely  found  in  the  ashes  of 
plants,*  but  silica  is  always  present,  having 

*  Alumina  is  generally  supposed  to  be  a  com- 
mon ingredient  of  the  ashes  of  plants,  and  it  is 


in  most  places  entered  the  plants  by  means 
of  alkalies.  In  order  to  form  a  distinct  con- 
ception of  the  quantities  of  alkalies  in  alu- 
minous minerals,  it  must  be  remembered 
that  felspar  contains  17|  per  cent,  of  potash, 
albite  1 1-43  per  cent,  of  soda,  and  mica  3 — 5 
per  cent.;  and  that  zeolite  contains  13 — 16 
per  cent,  of  both  alkalies  taken  together. 
The  late  analyses  of  Ch.  Gmelin,  Lowe, 
Fricke,  Meyer,  and  Redtenbacher,  have  also 
shown,  that  basalt  contains  from  |  to  3  per 
cent,  of  potash,  and  from  5 — 7  per  cent,  of 
soda,  that  clay  slate  contains  from  2-75 — 3-31 
per  cent,  of  potash,  and  loam  froml  £— ^4  per 
cent,  of  potash. 

If,  now,  we  calculate  from  these  data,  and 
from  the  specific  weights  of  the  different 
substances,  how  much  potash  must  be  con- 
tained in  a  layer  of  soil,  which  has  been 
formed  by  the  disintegration  of  26,910  square 
feet  (1  Hessian  acre^  of  one  of  these  rocks 
to  the  depth  of  20  inches,  we  find  that  a 
soil  of 

Felspar      contains 1,675,000  Ibs. 

Clink-stone     "       from  220,000  to  440,000   " 

Basalt              "          "       52,300  "  82,600    " 

Clay-slate       "          "     110,000  "  220,000   " 

Loam,              "          "       95,000  "  330,000   " 

Potash  is  present  in  all  clays  ;  according  to 
Fuchs,  it  is  contained  even  in  marl ;  it  has 
been  found  in  all  the  argillaceous  earths  in 
which  it  has  been  sought.  The  fact  that 
they  contain  potash  may  be  proved  in  the 
clays  of  the  transition  and  stratified  moun- 
tains, as  well  as  in  the  recent  formations 
surrounding  Berlin,  by  simply  digesting 
them  with  sulphuric  acid,  by  which  process 
alum  is  formed.  (Mitscherlich.)  It  is  well 
known  also  to  all  manufacturers  of  alum, 
that  the  leys  contain  a  certain  quantity  of 
this  salt  ready  formed,  the  potash,  of  which 
has  its  origin  from  the  ashes  of  the  stone 
and  brown  coal,  which  contain  much  argil- 
laceous earth. 

When  we  consider  this  extraordinary  dis- 
tribution of  potash  over  the  surface  of  the 
earth,  is  it  reasonable  to  have  recourse  to 
the  idea,  that  the  presence  of  this  alkali  in 
plants  is  due  to  the  generation  of  a  metallic 
oxide  by  a  peculiar  organic  process  from  the 
component  parts  of  the  atmosphere  ?  This 
opinion  found  adherents  even  after  the 
method  of  detecting  potash  in  soils  was 
known,  and  suppositions  of  the  same  kind 
may  be  found  even  in  the  writings  of  some 
physiologists  of  the  present  day.  Such 
opinions  belong  properly  to  the  time  when 
flint  was  conceived  to  be  a  product  of  chalk, 
and  when  every  thing  which  appeared  in- 
comprehensible on  account  of  not  having 
been  investigated,  was  explained  by  assump- 
tions far  more  incomprehensible. 


very  frequently  stated  in  the  results  of  their 
analyses  ;  but  in  most  cases  it  has  been  mistaken 
for  phosphate  of  magnesia,  or  phosphate  of  alu- 
mina, with  which  it  has  many  properties  in  com- 
mon,  and  from  which  it  cannot  be  distinguished 
without  much  care  and  attention. — ED. 


THE   ART   OF   CULTURE. 


51 


A  thousandth  part  of  loam  mixed  with 
the  quartz  in  new  red  sandstone,  or  with 
the  lime  in  the  different  limestone  forma- 
tions, affords  as  much  potash  to  a  soil  only 
twenty  inches  in  depth  as  is  sufficient  to 
supply  a  forest  of  pines  growing  upon  it 
for  a  century.  A  single  cubic  foot  of  felspar 
is  sufficient  to  supply  a  wood,  covering  a 
surface  of  26,910  square  feet,  with  the 
potash  required  for  five  years. 

Land  of  the  greatest  fertility  contains 
argillaceous  earths  and  other  disintegrated 
minerals  with  chalk  and  sand  in  such  a  pro- 
portion as  to  give  free  access  to  air  and 
moisture.  The  land  in  the  vicinity  of  Vesu- 
vius may  be  considered  as  the  type  of  a  fer- 
tile soil,  and  its  fertility  is  greater  or  less  in 
different  parts,  according  to  the  proportion 
of  clay  or  sand  which  it  contains. 

The  soil  which  is  formed  by  the  disinte- 
gration of  lava,  cannot  possibly,  on  account 
of  its  origin,  contain  the  smallest  trace  of 
vegetable  matter,  and '  yet  it  is  well  known 
that  when  the  volcanic  ashes  have  been  ex- 
posed for  some  time  to  the  influence  of  air 
and  moisture,  a  soil  is  gradually  formed  in 
which  all  kinds  of  plants  grow  with  the 
greatest  luxuriance.  This  fertility  is  owing 
to  the  alkalies  which  are  contained  in  the 
lava,  add  which  by  exposure  to  the  weather 
are  rendered  capable  of  being  absorbed  by 
plants.  Thousands  of  years  have  been  ne- 
cessary to  convert  stones  and  rocks  into  the 
soil  of  arable  land,  and  thousands  of  years 
more  will  be  requisite  for  their .  perfect  re- 
duction, that  is,  for  the  complete  exhaustion 
of  their  alkalies. 

We  see  from  the  composition  of  the  water 
in  rivers,  streamlets,  and  springs,  how  little 
rain-water  is  able  to  extract  alkali  from  a 
soil,  even  after  a  term  of  years  ;  this  water 
is  generally  soft,  and  the  common  salt, 
which  even  the  softest  invariably  contains, 
proves  that  those  alkaline  salts,  which  are 
carried  to  the  sea  by  rivers  and  streams, 
are  returned  again  to  the  land  by  wind  and 
rain. 

Nature  itself  shows  us  what  plants  re- 
quire at  the  commencement  of  the  develope- 
ment  of  their  germs  and  first  radicle  fibres. 
Bequerel  has  shown  that  the  gramince, 
leguminosce,  cruciferce,  cichoracece,  umhelli- 
feraz,  com/era,  and  cucurbitacece  emit  acetic 
acid  during  germination.  A  plant  which 
has  just  broken  through  the  soil,  and  a  leaf 
just  burst  open  from  the  bud,  furnish  ashes 
by  incineration,  which  contain  as  much, 
and  generally  more,  of  alkaline  salts  than 
at  any  period  of  their  life.  (De  Saussure.) 
Now  we  know  also,  from  the  experiments 
of  Bequerel,  in  what  manner  these  alkaline 
salts  enter  young  plants;  the  acetic  acid 
formed  during  germination  is  diffused 
through  the  wet  or  moist  soil,  becomes 
saturated  with  lime,  magnesia,  and  alkalies, 
and  is  again  absorbed  by  the  radicle  fibres 
in  the  form  of  neutral  salts.  After  the  ces- 
sation of  life,  when  plants  are  subjected  to 
decomposition  by  means  of  decay  and  putre- 


faction, the  soil  receives  again  that  which 
had  been  extracted  from  it. 

Let  us  suppose  that  a  soil  has  been  formed 
by  the  action  of  the  weather  on  the  compo- 
nent parts  of  granite,  grauwacke,  mountain 
limestone,  or  porphyry,  and  that  nothing  has 
vegetated  on  it  for  thousands  of  years. 
Now  this  soil  would  become  a  magazine  of 
alkalies  in  a  condition  favourable  for  their 
assimilation  by  the  roots  of  plants. 

The  interesting  experiments  of  Struve 
have  proved  that  water  impregnated  with 
carbonic  acid  decomposes  rocks  which  con- 
tain alkalies,  and  then  dissolves  a  part  of 
the  alkaline  carbonates.  It  is  evident  that 
plants  also,  by  producing  carbonic  acid 
during  their  decay,  and  by  means  of  the 
acids  which  exude  from  their  roots  in  the 
living  state,  contribute  no  less  powerfully  to 
destroy  the  coherence  of  rocks.  Next  to  the 
action  of  air,  water,  and  change  of  tempera- 
ture, plants  themselves  are  the  most  power- 
ful agents  in  effecting  the  disintegration  of 
rocks. 

Air,  water,  and  the  change  of  temperature 
prepare  the  different  species  of  rocks  for 
yielding  to  plants  the  alkalies  which  they 
contain.  A  soil  which  has  been  exposed 
for  centuries  to  all  the  influences  which 
affect  the  disintegration  of  rocks,  but  from 
which  the  alkalies  have  not  been  removed, 
will  be  able  to  afford  the  means  of  nourish 
ment  to  those  vegetables  which  require 
alkalies  for  its  growth  during  many  years  • 
but  it  must  gradually  become  exhausted, 
unless  those  alkalies  which  have  been  re- 
moved are  again  replaced ;  a  period,  there- 
fore, will  arrive  when  it  will  be  necessary 
to  expose  it  from  time  to  time  to  a  farther 
disintegration,  in  order  to  obtain  a  new  sup- 
ply of  soluble  alkalies.  For  small  as  is  the 
quantity  of  alkali  which  plants  require,  it  is 
nevertheless  quite  indispensable  for  their 
perfect  developement.  But  when  one  or 
more  years  have  elapsed  without  any  alka- 
lies having  been  extracted  from  the  soil,  a 
new  harvest  may  be  expected. 

The  first  colonists  of  Virginia  found  a 
country  the  soil  of  which  was  similar  to  that 
mentioned  above ;  harvests  of  wheat  and 
tobacco  were  obtained  for  a  century  from 
one  and  the  same  field,  without  the  aid  of 
manure ;  but  now  whole  districts  are  con- 
verted into  unfruitful  pasture-land,  which 
without  manure  produces  neither  wheat  nor 
tobacco.  From  every  acre  of  this  land  there 
were  removed  in  the  space  of  one  hundred 
years  12,000  Ibs.  of  alkalies  in  leaves,  grain, 
and  straw ;  it  became  unfruitful,  therefore, 
because  it  was  deprived  of  every  particle  of 
alkali,  which  had  been  reduced  to  a  soluble 
state,  and  because  that  which  was  rendered 
soluble  again  in  the  space  of  one  year  was 
not  sufficient  to  satisfy  the  demands  of  the 
plants.  Almost  all  the  cultivated  land  in 
Europe  is  in  this  condition ;  fallow  is  the 
term  applied  to  land  left  at  rest  for  farther 
disintegration.  It  is  the  greatest  possible 
mistake  to  suppose  that  the  temporary  dimi- 


AGRICULTURAL   CHEMISTRY. 


nution  of  fertility  ID  a  soil  is  owing  to  the 
loss  of  humus ;  it  is  the  mere  consequence 
of  the  exhaustion  of  the  alkalies. 

Let  us  consider  the  condition  of  the  coun- 
try around  Naples,  which  is  famed  for  its 
fruitful  corn-land  ;  the  farms  and  villages 
are  situated  from  eighteen  to  twenty-four 
miles  distant  from  one  another,  and  between 
them  there  are  no-  roads,  and  consequently 
no  transportation  of  manure.  Now  corn 
has  been  cultivated  on  this  land  for  thousands 
of  years,  without  any  part  of  that  which  is 
annually  removed  from  the  soil  being  artifi- 
cially restored  to  it.  How  can  any  influ- 
ence" be  ascribed  to  humus  under  such  cir- 
cumstances, when  it  is  not  even  known 
whether  humus  was  ever  contained  in  the 
soil? 

The  method  of  culture  in  that  district 
completely  explains  the  permanent  fertility. 
It  appears  very  bad  in  the  eyes  of  our  agri- 
culturists, but  there  it  is  the  best  plan  which 
could  be  adopted.  A  field  is  cultivated  once 
every  three  years,  and  is  in  the  intervals 
allowed  to  serve  as  a  sparing  pasture  for 
cattle.  The  soil  experiences  no  change  in 
the  two  years  during  which  it  there  lies  fal- 
low, farther  than  that  it  is  exposed  to  the 
influence  of  the  weather,  by  which  a  fresh 
portion  of  the  alkalies  contained  in  it  are 
again  set  free  or  rendered  soluble.  The  ani- 
mals fed  on  these  fields  yield  nothing  to 
these  soils  which  they  did  not  formerly  pos- 
sess. The  weeds  upon  which  they  live 
spring  from  the  soil,  and  that  which  they 
return  to  it  as  excrement  must  always  be  less 
than  that  which  they  extract.  The  fields, 
therefore,  can  have  gained  nothing  from  the 
mere  feeding  of  cattle  upon  them ;  on  the 
contrary,  the  soil  must  have  lost  some  of  its 
constituents. 

Experience  has  shown  in  agriculture 
that  wheat  should  not  be  cultivated  after 
wheat  on  the  same  soil,  for  it  belongs  with 
tobacco  to  the  plants  which  exhaust  a  soil. 
But  if  the  humus  of  a  soil  gives  it  the  power 
of  producing  corn,  how  happens  it  that 
wheat  does  not  thrive  in  many  parts  of 
Brazil,  where  the  soils  are  particularly  rich 
m  this  substance,  or  in  our  own  climate,  in 
soils  formed  of  mouldered  wood ;  that  its 
stalk  under  these  circumstances  attains  no 
strength,  and  droops  prematurely  ?  The 
cause  is  this,  that  the  strength  of  the  stalk  is 
due  to  silicate  of  potash,  and  that  the  corn 
requires  phosphate  of  magnesia,  neither  of 
which  substances  a  soil  of  humus  can  afford, 
since  it  does  not  contain  them;  the  plant 
may,  indeed,  under  such  circumstances,  be- 
come an  herb,  but  will  not  bear  fruit. 

Again,  how  does  it  happen  that  wheat 
does  not  flourish  on  a  sandy  soil,  and  that  a 
calcareous  soil  is  also  unsuitable  for  its 
growth,  unless  it  be  mixed  with  a  consider- 
able quantity  of  clay  ?*  It  is  because  these 


*  In  consequence  of  these  remarks  in  the  former 
edition  of  this  work,  Professor  Wohler  of  Gottin- 
gen  has  made  several  accurate  analyses  of  diffe- 


soils  do  not  contain  alkalies  in  sufficient 
quantity,  the  growth  of  wheat  being  arrested 
by  this  circumstance,  even  should  all  othei 
substances  be  presented  in  abundance. 

It  is  not  mere  accident  that  only  trees  ot 
the  fir  tribe  grow  on  the  sandstone  and  lime- 
stone of  the  Carpathian  mountains  and  the 
Jura,  whilst  we  find  on  soils  of  gneiss,  mica- 
slate,  and  granite  in  Bavaria,  of  clinkstone 
on  the  Rhone,  of  basalt  in  Vogelsberge,  and 
of  clay-slate  on  the  Rhine  and  Eifel,  the 
finest  forests  of  other  trees,  which  cannot  be 
produced  on  the  sandy  or  calcareous  soils 
upon  which  pines  thrive.  It  is  explained 
by  the  fact  that  trees,  the  leaves  of  which 
are  renewed  annually,  require  for  their 
leaves  six  to  ten  times  more  alkalies  than  the 
iir-tree  or  pine,  and  hence  when  they  are 
placed  in  soils  in  which  alkalies  are  con- 
tained in  very  small  quantity,  do  not  attain 
maturity.*  When  we  see  such  trees  grow- 
ing on  a  sandy  or  calcareous  soil — the  red- 
beech,  the  service-tree,  and  the  wild-cherry 
for  example,  thriving  luxuriantly  on  lime 
stone,  we  may  be  assured  that  alkalies  are 
present  in  the  soil,  for  they  are  necessary  to 
their  existence.  Can  we,  then,  regard  it  a? 
remarkable  that  such  trees  should  thrive  in 
America,  on  those  spots  on  which  forests 
of  pines  which  have  grown  and  collected 
alkalies  for  centuries,  have  been  burnt,  and 
to  which  the  alkalies  are  thus  at  once  re- 
stored ;  or  that  the  Spartium  scoparium, 
Erysimum  latifolium,  Blitum  capital  um,  *Se- 
necio  viscosus,  plants  remarkable  for  the 
quantity  of  alkalies  contained  in  thf:«  ashes, 
should  grow  with  the  greatest  luxuriance  on 
the  localities  of  conflagrations  ?f 

Wheat  will  not  grow  on  a  soil  which  has 
produced  wormwood,  and  vice  versa,  worm- 
wood does  not  thrive  where  wheat  has 
grown,  because  they  are  mutually  preju- 
dicial by  appropriating  the  alkalies  of  the 
soil. 

One  hundred  parts  of  the  stalks  of  wheat 
yield  15-5  parts  of  ashes  (H.  Davy;)  the 
same  quantity  of  the  dry  stalks  of  barley, 


rent  kinds  of  limestone  belonging  to  the  secondary 
and  tertiary  formations.  He  obtained  the  remark- 
able result,  that  all  those  limestones,  by  the  dis- 
integration of  which  soils  adapted  for  the  culture 
of  wheat  are  formed,  invariably  contain  a  certain 
quantity  of  potash.  The  same  observation  has 
also  recently  been  made  by  M.  Kuhlman  of  Lille. 
The  latter  observed  that  the  efflorescence  on  the 
mortar  of  walls  consists  of  the  carbonates  of  soda 
and  potash. 

*  One  thousand  parts  of  the  dry  leaves  of  oaks 
yielded  55  parts  of  ashes,  of  which  24  parts  con- 
sisted of  alkalies  soluble  in  water ;  the  same 
quantity  of  pine-leaves  gave  only  29  parts  of  ashes, 
which  contain  4.6  parts  of  soluble  salts.  (De 
Saussure.) 

t  After  the  great  fire  in  London,  large  quanti- 
ties of  the  Erysimum  latifolium  where  observed 
growing  on  the  spots  where  a  fire  had  taken  place. 
On  a  similar  occasion  the  Blitum  capitalum  was 
seen  at  Copenhagen,  the  Senecio  viscosus  in  Nas- 
sau, and  the  Spartium  scoparium  in  Languedoc. 
After  the  burnings  of  forests  of  pines  in  North 
America,  poplars  grew  on  the  same  soil. 


THE    ART    OF    CULTURE. 


53 


8'54  parts  (Schrader;)  and  one  hundred 
parts  of  the  stalks  of  oats,  only  4-42 ; — the 
ashes  of  all  these  are  of  the  same  compo- 
sition. 

We  nave  in  these  facts  a  clear  proof  of 
what  plants  require  for  their  growth.  Upon 
the  same  field,  which  will  yield  only  one 
harvest  of  wheat,  two  crops  of  barley  and 
three  of  oats  may  be  raised. 

All  plants  of  the  grass  kind  require  sili- 
cate of  potash.  Now  this  is  conveyed  to 
the  soil,  or  rendered  soluble  in  it  by  the  irri- 
gation of  meadows.  The  equiselacece,  the 
reeds  and  species  of  cane,  for  example, 
which  contain  such  large  quantities  of  sili- 
ceous earth,  or  silicate  of  potash,  thrive 
luxuriantly  in  marshes,  in  argillaceous  soils, 
and  in  ditches,  streamlets,  and  other  places 
where  the  change  of  water  renews  con- 
stantly the  supply  of  dissolved  silica.  The 
amount  of  silicate  of  potash  removed  from 
a  meadow  in  the  form  of  hay  is  very  con- 
siderable. We  need  only  call  to  mind  the 
melted  vitreous  mass  found  on  a  meadow 
between  Manheim  and  Heidelberg  after  a 
thunder-storm.  This  mass  was  at  first  sup- 
posed to  be  a  meteor,  but  was  found  on  ex- 
amination (by  Gmelin)  to  consist  of  silicate 
of  potash ;  a  flash  of  lightning  had  struck  a 
stack  of  hay,  and  nothing  was  found  in  its 
place  except  the  melted  ashes  of  the  hay. 

Potash  is  not  the  only  substance  necessary 
for  the  existence  of  most  plants ;  indeed  it 
has  been  already  shown  that  the  potash  may 
be  replaced  in  many  cases  by  soda,  magne- 
sia, or  lime;  but  other  substances  besides 
alkalies  are  required  to  sustain  the  life  of 
plants. 

Phosphoric  acid  has  been  found  in  the 
ashes  of  all  plants  hitherto  examined,  and 
always  in  combination  with  alkalies  or  alka- 
line earths.*  Most  seeds  contain  certain 
quantities  of  phosphates.  In  the  seeds  of 
different  kinds  of  corn  particularly,  there  is 
abundance  of  phosphate  of  magnesia. 

Plants  obtain  their  phosphoric  acid  from 
the  soil.  It  is  a  constituent  of  all  land  capa- 
ble of  cultivation,  and  even  the  heath  at 
Luneburg  contains  it  in  appreciable  quan- 
tity. Phosphoric  acid  has  been  detected 


*  Professor  Connall  was  lately  kind  enough  to 
show  me  about  half  an  ounce  of  a  saline  powder, 
which  had  been  taken  from  an  interstice  in  the 
body  of  a  piece  of  teak  timber.  It  consisted  es- 
sentially of  phosphate  of  lime,  with  small  quan- 
tities of  carbonate  of  lime  and  phosphate  of  mag- 
nesia. This  powder  had  been  sent  to  Sir  David 
Brewster  from  India,  with  the  assurance  that  it 
was  the  same  substance  which  usually  is  found  in 
the  hollows  of  teak  timber.  It  has  long  been 
known  that  silica,  in  the  form  of  tabasheer,  is  se- 
creted by  the  bamboo ;  but  I  am  not  aware  that 
phosphates  have  been  found  in  the  same  condi- 
tion. Without  more  precise  information,  we  must 
therefore  suppose  that  they  are  left  in  the  hollows 
by  the  decay  of  the  wood.  Decay  is  a  slow  pro- 
cess of  combustion,  and  the  incombustible  ashes 
must  remain  after  the  organic  matter  has  been 
consumed.  But  if  this  explanation  be  correct,  the 
wood  of  the  teak-tree  must  contain  an  enormous 
quantity  of  earthy  phosphates. — ED. 


also  in  all  mineral  waters  in  which  its  pre- 
sence has  been  tested ;  and  in  those  in 
which  it  has  not  been  found  it  has  not  been 
sought  for.  The  most  superficial  strata  of 
the  deposits  of  sulphuret  of  lead  (galena) 
contain  crystallised  phosphate  of  lead  (green- 
lead  ore;)  clay-slate,  which  forms  extensive 
strata,  is  covered  in  many  places  with  crys- 
tals of  phosphate  of  alumina  (Wavellite ;) 
all  its  fractured  surfaces  are  overlaid  with  it. 
Phosphate  of  lime  Apatite)  is  found  even 
in  the  volcanic  boulders  on  the  Laacher 
See  in  the  Eifel,near  Andernach.* 

The  soil  in  which  plants  grow  furnishes 
them  with  phosphoric  acid,  and  they  in  turn 
yield  it  to  animals,  to  be  used  in  the  forma- 
tion of  their  bones,  and  of  those  constituents 
of  the  brain  which  contain  phosphorus. 
Much  more  phosphorus  is  thus  afforded  to 
the  body  than  it  requires,  when  flesh,  bread, 
fruit,  and  husks  of  grain  are  used  for  food, 
and  this  excess  is  eliminated  in  the  urine 
and  the  solid  excrements.  We  may  form 
an  idea  of  the  quantity  of  phosphate  of 
magnesia  contained  in  grain,  when  we  con- 
sider that  the  concretions  in  the  caecum  of 
horses  consist  of  phosphate  of  magnesia 
and  ammonia,  which  must  have  been  ob- 
tained from  the  hay  and  oats  consumed  as 
food.  Twenty-nine  of  these  stones  were 
taken  after  death  from  the  rectum  of  a  horse 
belonging  to  a  miller,  in  Eberstadt,  the  total 
weight  of  which  amounted  to  3  Ibs. ;  and 
Dr.  F.  Simon  has  latelv  described  a  similar 
concretion  found  in  tne  norse  ol  a  carrier, 
which  weighed  l£  Ib. 

It  is  evident  that  the  seeds  of  corn  could 
not  be  formed  without  phosphate  of  magne- 
sia, which  is  one  of  their  invariable  con- 
stituents; the  plant  could  not  under  such 
circumstances  reach  maturity. 

Some  plants,  however,  extract- other  mat- 
ters from  the  soil  besides  silica,  potash,  and 
phosphoric  acid,  which  are  essential  con- 
stituents of  the  plants  ordinarily  cultivated .f 
These  other  matters,  we  must  suppose, 
supply,  in  part  at  least,  the  place  and  per- 
form the  functions  of  the  substances  just 
named.  We  may  thus  regard  common  salt, 
sulphate  of  potash,  nitre,  chloride  of  potas- 
sium, and  other  matters,  as  necessary  con- 
stituents of  several  plants. 

Clay-slate  contains  generally  small  quan- 
tities of  oxide  of  copper;  and  soils  formed 
from  micaceous  schist  contain  some  metallic 
fluorides.  Now,  small  quantities  of  these 
substances  also  are  absorbed  into  plants,  al- 
though we  cannot  affirm  that  they  are  ne- 
cessary to  them. 

It  appears  that  in  certain  cases  flouride  of 
calcium  may  take  the  place  of  phosphate 
of  lime  in  the  bones  and  teeth;  at  least  it  is 
impossible  otherwise  to  explain  its  constant 
presence  in  the  bones  of  antediluvian  ani- 
mals, by  which  they  are  distinguished  from 


*  See  the  analyses  of  soils  in  the  Appendix, 
t  For  more  minute  information  regarding  soilg 
see  the  supplementary  chapter  at  the  end  of  Part  1, 


54 


AGRICULTURAL    2HEMISTRY. 


those  of  a  later  period.     The  bones  of  hu-  |  belong  to  those  which  are  termed  fellow- 


man  skulls  found  at  Pompeii  contain  as 
much  fluoric  acid  as  those  of  animals  of  a 
former  world,  for  if  they  be  placed  in  a  state 
of  powder  in  glass  vessels,  and  digested 
with  sulphuric  acid,  the  interior  of  the  ves- 
sel will,  after  twenty-four  hours,  be  found 
powerfully  corroded  (Liebig;)  whilst  the 
bones  and  teeth  of  animals  of  the  present 
day  contain  only  traces  of  it.  (Berzelius.) 

De  Saussure  remarked  that  plants  require 
quantities  of  the  component  parts  of  soils  in 
different  stages  of  their  developement;  an 
observation  of  much  importance  in  consider- 
ing the  growth  of  plants.  Thus  wheat 
yielded  79-1000  of  ashes  a  month  before  blos- 
soming, 54-1000  while  in  blossom,  and 
33-1000  after  the  ripening  of  the  seeds.  It 
is  therefore  evident  that  wheat,  from  the 
time  of  its  flowering,  restores  a  part  of  its 
organic  constituents  to  the  soil,  although  the 
phosphate  of  magnesia  remains  in  the  seeds. 

The  fallow-time,  as  we  have  already 
shown,  is  that  period  of  culture  during 
which  land  is  exposed  to  a  progressive  dis- 
integration by  means  of  the  influence  of  the 
atmosphere,  for  the  purpose  of  rendering  a 
certain  quantity  of  alkalies  capable  of  being 
appropriated  by  plants. 

NOAV,  it  is  evident,  that  the  careful  tilling 
of  fallow-land  must  increase  and  accelerate 
this  disintegration.  For  the  purpose  of  agri- 
culture, it  is  quite  indifferent,  whether  the 
land  is  covered  with  weeds,  or  with  a  plant 
which  does  not  abstract  the  potash  inclosed 
in  it.  Now  many  plants  in  the  family  of 
the  leguminosce  are  remarkable  on  account 
of  the  small  quantity  of  alkalies  or  salts  in 
general  which  they  contain ;  the  Windsor 
bean  (ViciaFaba,}  for  example,  contains  no 
free  alkalies,  and  not  one  per  cent,  of  the 
phosphates  of  lime  and  magnesia.  (Einhof.) 
The  bean  of  the  kidney-bean  (Phascolus 


contains  only  traces  of  salts.  (Bra- 
connut.)  The  stem  of  lucerne  (Medicago 
sativit)  contains  only  0.83  per  cent.,  that  of 
the  lentil  (Ervum  Lens)  only  0.57  of  phos- 
phate of  lime  with  albumen.  (Crome.) 
Buck- wheat  dried  in  the  sun  yields  only 
0.681  per  cent,  of  ashes,  of  which  0.09  parts 
are  soluble  salts.  (Zenneck.)*  These  plants 


*  The  small  quantity  of  phosphates  which  th( 
seeds  of  the  lentils,  beans,  and  peas  contain,  mus 
be  the  cause  of  their  small  value  as  articles  of  nour 
ishment, since  they  surpass  all  other  vegetable  fooc 
in  the  quantity  of  nitrogen  which  enters  into  their 
composition.  "  But  as  the  component  parts  of  the 
bones  (phosphate  of  lime  and  magnesia)  are  absent 
they  satisfy  the  appetite  without  increasing  the 
strength.  The  following  is  an  analysis  of  lentil 
(Playfair.)  6.092  grammes  lost  0.972  grammes  oi 
water  at  212°.  0.566  grammes,  burned  with  ox 
ide  of  copper,  gave  0.910  grammes  carbonic  acic 
and  0.336  grammes  of  water.  The  lentils  o: 
combustion  with  oxide  of  copper,  yielded  a  gas 
in  which  the  proportion  of  the  nitrogen  to  the  car 
bonic  acid  was  as  1  to  16. 

Carbon         44.45 

Hydro-en      6.59 

Nitrogen       6.42 

Water          15.95 


rops,  and  the  cause  wherefore  they  do  not 
xercise  any  injurious  influence  on  corn 
•vhich  is  cultivated  immediately  after  them 

that  they  do  not  extract  the  alkalies  of 
he  soil,  and  only  a  very  small  quantity  of 
>hosphates. 

It  is  evident  that  two  plants  growing  be- 

ide  each  other  will  mutually   injure    one 

mother,  if  they   withdraw  the  same   food 

rom  the -soil.     Hence  it  is  riot  surprising 

hat  the  wild  chamomile  (Matricaria  Chamo- 

milla)  and  Scotch-broom  (Spartium  Scopa- 

rium)  impede  the  growth  of  corn,  when  it 

considered  that  both  yield  from  7  to  7.43 
>er  cent,  of  ashes,  which  contain  ^  of  car- 
>onate  of  potash.  The  darnel  and  the  flea- 
)ane  (Erigeron  acre)  blossom  and  bear  fruit 
at  the  same  time  as  com,  so  that  when 
growing  mingled  with  it,  they  will  partake 
f  the  component  parts  of  the  soil,  and  in 
proportion  to  the  vigour  of  their  growth, 
hat  of  the  corn  must  decrease;  for  what 
one  receives,  the  others  are  deprived  of. 
Plants  will,  on  the  contrary,  thrive  beside 
each  other,  either  when  the  substances 
necessary  for  their  growth  which  they  ex- 
tract from  the  soil  are  of  different  kinds,  or 
when  they  themselves  are  not  both  in  the 
same  stages  of  developement  at  the  same  time. 

On  a  soil,  for  example,  which  contains 
potash,  both  wheat  and  tobacco  may  be 
reared  in  succession,  because  the  latter  plant 
does  not  require  phosphates,  salts  which  are 
invariably  present  in  wheat,  but  requires 
only  alkalies,  and  food  containing  nitrogen. 

According  to  the  analysis  of  Posselt  and 
Riemann,  10,000  parts  of  the  leaves  of  the 
tobacco-plant  contain  16  parts  of  phosphate 
of  lime,  8.8  parts  of  silica,  and  no  magnesia; 
whilst  an  equal  quantity  of  wheat  straw 
contains  47.3  parts,  and  the  same  quantity 
of  the  grain  of  wheat  99.45  parts  of  phos- 
phates. (De  Saussure.) 

Now,  if  we  suppose  that  the  grain  of 
wheat  is  equal  to  half  the  weight  of  its 
straw,  then  the  quantity  of  phosphates  ex- 
tracted from  a  soil  by  the  same  weights  of 
wheat  and  tobacco  must  be  as  97.7  :  16. 
This  difference  is  very  considerable.  The 
roots  of  tobacco,  as  well  as  those  of  wheat, 
extract  the  phosphates  contained  in  the  soil, 
but  they  restore  them  again,  because  they 
are  not  essentially  necessary  to  the  deve- 
lopement  of  the  plant. 


CHAPTER  VIII. 

ON   THE    ALTERNATION    OF    CROPS. 

T  has  .ong  since  been  found  by  experience, 
that  the  growth  of  annual  plants  is  rendered 
imperfect,  and  their  crops  of  fruit  or  herbs 
less  abundant,  by  cultivating  them  in  suc- 
cessive years  on  the  same  soil,  and  that,  in 
spite  of  the  loss  of  time,  a  greater  quantitv 
of  grain  is  obtained  when  a  field  is  allowed 


ALTERNATION   OF   C 


to  lie  uncultivated  for  a  year.  During  this 
interval  of  rest,  the  soil,  in  a  great  measure, 
regains  its  original  fertility. 

It  has  been  further  observed,  that  certain 
plants,  such  as  peas,  clover,  and  flax,  thrive 
on  the  same  soil  only  after  a  lapse  of  years ; 
whilst  others,  such  as  hemp,  tobacco,  hclian- 
thus  tuberosus,  rye,  and  oats  may  be  culti- 
vated in  close  succession  when  proper  ma- 
nure is  used.  It  has  also  been  found,  that  se- 
veral of  these  plants  improve  the  soil,  whilst 
others,  and  these  are  the  most  numerous, 
impoverish  or  exhaust  it.  Fallow  turnips, 
cabbage,  beet,  spelt,  summer  and  winter 
barley,  rye  and  oats,  are  considered  to  be- 
long to  the  class  which  impoverish  a  soil ; 
whilst  by  wheat,  hops,  madder,  late  turnips, 
hemp,  poppies,  teasel,  flax,  weld,  and  lico- 
rice, it  is  supposed  to  be  entirely  exhausted. 

The  excrements  of  man  and  animals  have 
been  employed  from  the  earliest  times  for 
the  purpose  of  increasing  the  fertility  of 
soils  j  and  it  is  completely  established  by  all 
experience,  that  they  restore  certain  consti- 
tuents to  the  soil,  which  are  removed  with 
the  roots,  fruit  or  grain,  or  entire  plants 
grown  upon  it. 

But  it  has  been  observed  that  the  crops  are 
not  always  abundant  in  proportion  to  the 
quantity  of  manure  employed,  even  al- 
though it  may  have  been  of  the  most  power- 
ful kind ;  that  the  produce  of  many  plants, 
for  example,  diminishes,  in  spite  of  the  ap- 
parent replacement  by  manure  of  the  sub- 
stances removed  from  the  soil,  when  they 
are  cultivated  on  the  same  field  for  several 
years  in  succession. 

On  the  other  hand  it  has  been  remarked, 
that  a  field  which  has  become  unfitted  for  a 
certain  kind  of  plants  was  not  on  that  ac- 
count unsuited  for  another;  and  upon  this 
observation,  a  system  of  agriculture  has 
been  gradually  founded,  the  principal  ob- 
ject of  which  is  to  obtain  the  greatest  possi- 
ble produce  with  the  least  expense  of  ma- 
nure. 

Now  it  was  deduced  from  all  the  foregoing 
facts  that  plants  require  for  their  growth 
different  constituents  of  soil,  and  it  was 
very  soon  perceived,  that  an  alternation  of 
the  plants  cultivated  maintained  the  fertility 
of  a  soil  quite  as  well  as  leaving  it  at  rest  or 
fallow.  It  was  evident  that  all  plants  must 
give  back  to  the  soil  in  which  they  grow 
different  proportions  of  certain  substances, 
which  are  capable  of  being  used  as  food  by 
a  succeeding  generation. 

But  agriculture  has  hitherto  never  sought 
aid  from  chemical  principles,  based  on  the 
knowledge  of  those  substances  which  plants 
extract  from  the  soil  on  which  they  grow, 
and  of  those  restored  to  the  soil  by  means  of 
manure.  The  discovery  of  such  principles 
will  be  the  task  of  a  future  generation,  for 
what  can  be  expected  from  the  present, 
which  recoils  with  seeming  distrust  and 
aversion  from  all  the  means  of  assistance 
offered  it  by  chemistry,  and  which  does  not 
understand  the  art  of  making  a  rational  ap- 


plication of  chemical  discoveries?  A  futura 
generation,  However,  will  derive  incalcula- 
ble advantage  from  these  means  of  help. 

Of  all  the  views  which  have  been  adopted 
regarding  the  cause  of  the  favourable  effects 
of  the  alternations  of  crops,  that  proposed 
by  M.  Decandolle  alone  deserves  to  be  men- 
tioned as  resting  on  a  firm  basis. 

Decandolle  supposes  that  the  roots  of 
plants  imbibe  soluble  matter  of  every  kind 
from  the  soil,  and  thus  necessarily  absc.rb  a 
number  of  substances  which  are  not  adapted 
to  the  purposes  of  nutrition,  and  must  sub- 
sequently be  expelled  by  the  roots,  and  re- 
turned to  the  soil  as  excrements.  Now,  as 
excrements  cannot  be  assimilated  by  the 
plant  v/hich  ejected  them,  the  more  of  these 
matters  which  the  soil  contains,  the  more 
unfertile  must  it  be  for  the  plants  of  the 
same  species.  These  excrementitious  mat- 
ters may,  however,  still  be  capable  of  assi- 
milation by  another  kind  of  plants,  which 
would  thus  remove  them  from  the  soil,  and 
render  it  again  fertile  for  the  first.  And  if 
the  plants  last  grown  also  expel  substances 
from  their  roots,  which  can  be  appropriated 
as  food  by  the  former,  they  will  improve  the 
soil  in  two  ways. 

Now  a  great  number  of  facts  appear  at 
first  sight  to  give  a  high  degree  of  probabi- 
lity to  this  view.  Every  gardener  knows 
thai  a  fruit-tree  cannot  be  made  to  grow  on 
the  same  spot  where  another  of  the  same 
species  has  stood ;  at  least  not  until  after  a 
lapse  of  several  years.  Before  new  vine- 
stocks  are  planted  in  a  vineyard  from  which 
the  old  have  been  rooted  out,  other  plants 
are  cultivated  on  the  soil  for  several  years. 
In  connexion  with  this  it  has  been  observed, 
that  several  plants  thrive  best  when  growing 
beside  one  another;  and  on  the  contrary, 
that  others  mutually  prevent  each  other's 
developement.  Whence  it  was  concluded, 
that  the  beneficial  influence  in  the  former 
case  depended  on  a  mutual  interchange  of 
nutriment  between  the  plants,  and  the  in- 
jurious one  in  the  latter  on  a  poisonous 
j  action  of  the  excrements  of  each  on  the 
I  other  respectively. 

A   series    of  experiments    by   Macaire- 
Princep   gave  great  weight  to  this  theory. 
He    proved   beyond   all   doubt  that  many 
plants    are  capable  of   emitting   extractive 
matter  from  their  roots.     He  found  that  the 
excretions    were   greater  during   the  night 
than   by    day    (?),  and   that   the    water  in 
which  plants  of  the  family  of  the  Legumir- 
nosce  grew  acquired  a  brown  colour.     Plants 
of  the    same   species  placed  in  water  im- 
pregnated  with  these  excrements  were  im- 
peded  in  their  growth,  and   faded  prema- 
|  turely,  whilst,  on  the  contrary,  corn-plants 
I  grew  vigorously  in  it,  and  the  colour  of  the 
j  water  diminished    sensibly  ;  so   that  it  ap- 
i  peared  as  if  a  certain  quantity  of  the  excre- 
I  ments  of  the   Leguminosce  had  really  been 
j  absorbed    by    the    corn-plants.     These  ex- 
periments  afforded,  as    their    main   result, 
i  that  the  characters  and  properties  oi  the  ex 


56 


AGRICULTURAL   CHEMISTRY. 


rrements  of  different  species  of  plants  are 
different  from  one  another,  and  that  some 
plants  expel  excrementitious  matter  of  an 
acrid  and  resinous  character;  others  mild 
substances  resembling  gum.  The  former  of 
these,  according  to  Macaire- Princep,  may 
be  regarded  as  poisonous,  the  latter  as  nu- 
tritious. 

The  experiments  of  Macaire-Princep  af- 
ford positive  proof  that  the  roots,  probably 
of  all  plants,  expel  matters,  which  cannot 
be  converted  in  their  organism  either  into 
woody  fibre,  starch,  vegetable  albumen,  or 
gluten,  since  their  expulsion  indicates  that 
they  are  quite  unfitted  for  this  purpose. 
But  they  cannot  be  considered  as  a  confir- 
mation of  the  theory  of  Decandolle,  for  they 
leave  it  quite  undecided  whether  the  sub- 
stances were  extracted  from  the  soil,  or 
formed  by  the  plant  itself  from  food  received 
from  another  source.  It  is  certain  that  the 
gummy  and  resinous  excrements  observed 
by  Macaire-Princep  could  not  have  been 
contained  in  the  soil,  and  as  we  know  that 
the  carbon  of  a  soil  is  not  diminished  by 
culture,  but,  on  the  contrary,  increased,  we 
must  conclude  that  all  excrements  which 
contain  carbon  must  be  formed  from  the  food 
obtained  by  plants  from  the  atmosphere. 
Now,  these  excrements  are  compounds, 
produced  in  consequence  of  the  transforma- 
tions of  the  food,  and  of  th,:  new  forms 
which  it  assumes  by  entering  into  the  com- 
position of  tiie  various  organs. 

M.  Decandolle's  theory  is  properly  a 
modification  of  an  earlier  hypothesis,  which 
suppo-ed  that  the  roots  of  different  plants 
extracted  different  nutritive  substances  from 
the  soil,  each  plant  selecting  that  which 
was  exactly  suited  for  its  assimilation.  Ac- 
cording to  this  hypothesis,  the  matters  in- 
capablt  of  assimilation  are  not  extracted 
from  the  soil,  whilst  M.  Decandolle  consi- 
ders that  they  are  returned  to  it  in  the  form 
of  excrements.  Both  views  explain  how  it 
happens  that  after  corn,  corn  cannot  be 
raised  with  advantage,  nor  after  peas,  peas  ; 
but  they  do  not  explain  how  a  field  is  im- 
proved by  lying  fallow,  and  this  in  propor- 
tion to  the  care  with  which  it  is  tilled  and 
kept  free  from  weeds;  nor  do  they  show 
how  a  soil  gains  carbonaceous  matter  by  the 
cultivation  of  certain  plants,  such  as  lucerne 
and  sainfoin. 

Theoretical  considerations  on  the  process 
of  nutrition,  as  well  as  the  experience  of  all 
agriculturists,  so  beautifully  illustrated  by 
the  experiments  of  Macaire-Princep,  leave 
no  doubt  that  substances  are  excreted  from 
the  roots  of  plants,  and  that  these  matters 
form  the  means  by  which  the  carbon  re- 
ceived from  humus  in  the  early  period  of 
their  growth  is  restored  to  the  soil.  But 
we  may  now  inquire  whether  these  excre- 
ments, in  the  state  in  which  they  are  ex- 
pelled, are  capable  of  being  employed  as 
food  by  other  plants. 

The  excrements  of  a  carnivorous  animal 
contain  no  constituents  fitted  lor  the  nou- 


rishment of  another  of  the  same  species  j 
but  it  is  possible  that  an  herbivorous  animal, 
a  fish,  or  a  fowl,  might  find  in  them  undi- 
gested matters  capable  of  being  digested  in 
their  organism,  from  the  very  circumstance 
of  their  organs  of  digestion  having  a  different 
structure.  This  is  the  only  sense  in  which 
we  can  conceive  that  the  excrements  of  one 
animal  could  yield  matter  adapted  for  the 
nutrition  of  another. 

A  number  of  substances  contained  in  the 
food  of  animals  pass  through  their  alimentary 
organs  without  change,  and  are  expelled 
from  the  system ;  these  are  excrements  but 
not  excretions.  Now  a  part  of  such  excre- 
mentitious matter  might  be  assimilated  in 
passing  through  the  digestive  apparatus  of 
another  animal.  The  organs  of  secretion 
form  combinations  of  which  only  the  ele- 
ments were  contained  in  the  food.  The 
production  of  these  new  compounds  is  a 
consequence  of  the  changes  which  the  food 
undergoes  in  becoming  chyle  and  chyme, 
and  of  the  further  transformations  to  which 
these  are  subjected  by  entering  into  the 
composition  of  the  organism.  These  mat- 
ters, likewise,  are  eliminated  in  the  excre- 
ments, which  must  therefore  consist  of  two 
different  kinds  of  substances,  namely,  of  the 
indigestible  constituents  of  the  food,  and  of 
the  new  compounds  formed  by  the  vital  pro- 
cess. The  latter  substances  have  been  pro- 
duced in  consequence  of  the  formation  of 
fat,  muscular  fibre,  cerebral  and  nervous 
substance,  and  are  quite  incapable  of  being 
converted  into  the  same  substances  in  any 
other  animal  organism. 

Exactly  similar  conditions  must  subsist  in 
the  vital  processes  of  plants.  When  sub- 
stances which  are  incapable  of  being  em- 
ployed in  the  nutrition  of  a  plant  exist  in 
the  matter  absorbed  by  its  roots,  they  must 
be  again  returned  to  the  soil.  Such  excre- 
ments might  be  serviceable  and  even  indis- 
pensable to  the  existence  of  several  other 
plants.  But  substances  that  are  formed  in 
a  vegetable  organism  during  the  process  of 
nutrition,  which  are  produced,  therefore,  in 
consequence  of  the  formation  of  woody  fibre, 
starch,  albumen,  gum,  acids,  &c.,  cannot 
again  serve  in  any  other  plants  to  form  the 
same  constituents  of  vegetables. 

The  consideration  of  these  facts  enables 
us  to  distinguish  the  difference  between  the 
views  of  Decandolle  and  those  of  Macaire- 
Princep.  The  substances  which  the  former 
physiologist  viewed  as  excrements,  belonged 
to  the  soil;  they  were  undigested  matters, 
which  although  not  adapted  for  the  nutrition 
of  one  plant  might  yet  be  indispensable  to 
another.  Those  matters,  on  the  contrary, 
designated  as  excrements  by  Macaire-Prin- 
cep, could  only  in  one  form  serve  for  the 
nutrition  of  vegetables.  It  is  scarcely  ne- 
cessary to  remark  that  this  excrementitious 
matter  must  undergo  a  change  before  another 
season.  During  autumn  and  winter  it  be- 
gins to  suffer  a  change  from  the  influence 
of  air  and  water  j  its  putrefaction,  and  a* 


ALTERNATION    OF    CROPS. 


57 


»ength,  by  continued  contact  with  the  air, 
which  tillage  is  the  means  of  procuring,  its 
decay  are  effected;  and  at  the  commence- 
ment of  spring  it  has  become  converted, 
either  in  whole  or  in  part,  into  a  substance 
which  supplies  the  place  of  humus,  by  being 
a  constant  source  of  carbonic  acid. 

The  quickness  with  which  this  decay  of 
the  excrements  of  plants  proceeds  depends 
on  the  composition  of  the  soil,  and  on  its 
greater  or  less  porosity.  It  will  take  place 
very  quickly  in  a  calcareous  soil:  for  the 
power  of  organic  excrements  to  attract  oxy- 
gen and  to  putrefy  is  increased  by  contact 
with  the  alkaline  constituents,  and  by  the 
general  porous  nature  of  such  kinds  of  soil, 
which  freely  permit  the  access  of  air.  But 
it  requires  a  longer  time  in  heavy  soils  con- 
sisting of  loam  or  clay. 

The  same  plants  can  be  cultivated  with 
advantage  on  one  soil  after  the  second. year, 
but  in  others  not  until  the  fifth  or  ninth, 
merely  on  account  of  the  change  and  de- 
struction of  the  excrements,  which  have  an 
injurious  influence  on  the  plants  being  com- 
pleted in  the  one,  in  the  second  year ;  in  the 
others,  not  until  the  ninth. 

Jn  some  neighbourhoods  clover  will  not 
thrive  till  the  sixth  year,  in  others  not  till  the 
twelfth ;  flax  in  the  second  or  third  year. 
All  this  depends  on  the  chemical  nature  of 
the  soil,  for  it  has  been  found  by  experience 
that  in  those  districts  where  the  intervals  at 
which  the  same  plants  can  be  cultivated 
with  advantage  are  very  long,  the  time  can- 
not be  shortened  even  by  the  use  of  the  most 
powerful  manures.  The  destruction  of  the 
peculiar  excrements  of  one  crop  must  have 
taken  place  before  a  new  crop  can  be  pro- 
duced. 

Flax,  peas,  clover,  and  even  potatoes,  are 
plants  the  excrements  of  which,  in  argilla- 
ceous soils,  require  the  longest  time  for  their 
conversion  into  humus;  but  it  is  evident 
that  the  use  of  alkalies  and  burnt  lime,  or 
even  small  quantities  of  ashes  which  have 
not  been  lixiviated,  must  enable  a  soil  to 
permit  the  cultivation  of  the  same  plants  in 
a  much  shorter  time. 

A  soil  lying  fallow  owes  its  earlier  fer- 
tility, in  part,  to  the  destruction  or  conver- 
sion into  humus  of  the  excrements  contained 
in  it,  which  is  effected  during  the  fallow 
season,  at  the  same  time  that  the  land  is 
exposed  to  a  farther  disintegration. 

In  the  soils  in  the  neighbourhood  of  the 
Rhine  and  Nile,  which  contain  much  pot- 
ash, and  where  crops  can  be  obtained  in  close 
succession  from  the  same  field,  the  fallowing 
of  the  land  is  superseded  by  the  inundation  ; 
the  irrigation  of  meadows  effects  the  same 
purpose.  It  is  because  the  water  of  rivers 
and  streams  contains  oxygen  in  solution  that 
it  effects  the  most  complete  and  rapid  putre- 
faction of  the  excrements  contained  in  the 
soil  which  it  penetrates,  and  in  which  it  is 
continually  renewed.  If  it  was  the  water 
alone  which  produced  this  effect,  marshy 
meadows  should  be  most  fertile.  Hence  it 


is  not  sufficient  in  irrigating  meadows  to 
ccnvert  them  into  marshes,  by  covering  for 
several  months  their  surface  with  water, 
which  is  not  renewed;  for  the  advantage  of 
irrigation  consists  principally  in  supplying 
oxygen  to  the  roots  of  plants.  The  quantity 
of  water  necessary  for  this  purpose  is  very 
small,  so  that  it  is  sufficient  to  cover  the 
meadow  with  a  very  thin  layer,  if  this  be 
frequently  renewed. 

The  cultivation  of  meadows  forms  one  of 
the  most  important  branches  of  rural  eco- 
nomy. It  contributes  materially  to  the  pros- 
perity of  the  agriculturist  by  increasing  his 
stock  of  cattle,  and  consequently  by  furnish- 
ing him  with  manure,  which  may  be  applied 
to  the  augmentation  of  his  crops.  Indeed, 
th£  great  progress  which  has  been  made  in 
Germany  in  the  improvement  of  cattle  is 
mainly  attributable  to  the  attention  which  is 
devoted  in  that  country  to  the  culture  of 
meadows.  The  environs  of  Siegin,  in  Nas- 
sau, are  particularly  famed  in  this  respect, 
and  every  year  a  large  number  of  young 
farmers  repair  to  it,  for  the  purpose  of  study- 
ing this  branch  of  agriculture  in  situ.  In 
that  district  the  culture  of  grass  has  attained 
such  great  perfection,  that  the  produce  of 
their  meadow-land  far  exceeds  that  obtained 
in  any  other  part  of  Germany.  This  is  ef- 
fected simply  by  preparing  the  ground  in 
such  a  manner  as  to  enable  it  to  be  irrigated 
both  in  spring  and  in  autumn.  The  surface 
of  the  soil  is  fitted  to  suit  the  locality,  and 
the  quantity  of  water  which  can  be  com- 
manded. Thus  if  the  meadows  be  situated 
upon  a  declivity,  banks  of  from  one  to  two 
feet  in  height  are  raised  at  short  distances 
from  each  other.  The  water  is  admitted  by 
small  channels  upon  the  most  elevated  bank, 
and  allowed  to  discharge  itself  over  the  sides 
in  such  a  manner  as  to  run  upon  the  bank 
situated  below.  The  grass  grown  upon 
meadows  irrigated  in  this  way  is  three  or 
four  times  higher  than  that  obtained  from 
fields  which  are  covered  with  water  that  is 
deprived  of  all  egress  and  renewal. 

It  follows  from  what  has  preceded  that  the 
advantage  of  the  alternation  of  crops  is  ow- 
ing to  two  causes. 

A  fertile  soil  ought  to  afford  to  a  plant  all 
the  inorganic  bodies  indispensable  for  its  ex- 
istence in  sufficient  quantity  and  in  such 
condition  as  allows  their  absorption. 

All  plants  require  alkalies,  which  are 
contained  in  some,  in  the  GraminecB  for  ex- 
ample, in  the  form  of  silicates ;  in  otners, 
in  that  of  tartrates,  citrates,  acetates,  or  ox- 
alates. 

When  these  alkalies  are  in  combination 
with  silicic  acid,  the  ashes  obtained  by  the 
incineration  of  the  plant  contain  no  carbonic 
acid ;  but  when  they  are  united  with  organic 
acids,  the  addition  of  a  mineral  acid  to  their 
ashes  causes  an  effervescence. 

A  third  species  of  plants  requires  phos- 
phate of  lime,  another  phosphate  of  mag- 
nesia, and  several  do  not  thrive  without  car- 
bonate of  lime. 


58 


AGRICULTURAL  CHEMISTRY. 


Silicic  acid  is  the  first  solid  substance 
taken  up  by  plants;  it  appears  to  be  the  ma- 
terial from  which  the  formation  of  the  wood 
takes  its  origin,  acting  like  a  grain  of  sand 
around  which  the  first  crystals  form  in  a  so- 
lution of  a  salt  which  is  in  the  act  of  crys- 
tallising. Silicic  acid  appears  to  perform 
the  functions  of  woody  fibre  in  the  Equise- 
tacece  and  bamboos,*  just  as  the  crystalline 
salt,  oxalate  of  lime,,  does  in  many  of  the 
lichens. 

When  we  grow  in  the  same  soil  for  seve- 
ral years  in  succession  different  plants,  the 
first  of  which  leaves  behind  that  which  the 
second,  and  the  second  that  which  the  third 
may  require,  the  soil  will  be  a  fruitful  one 
for  all  the  three  kinds  of  produce.  If  the 
first  plant,  for  example,  be  wheat,  which 
consumes  the  greatest  part  of  the  silicate  of 
potash  in  a  soil,  whilst  the  plants  which 
succeed  it  are  of  such  a  kind  as  require 
only  small  quantities  of  potash,  as  is  the 
case  with  Leguminosce,  turnips,  potatoes, 
&c.,  the  wheat  may  be  again  sowed  with 
advantage  after  the  fourth  year ;  for  during 
the  interval  of  three  years  the  soil  will,  by 
the  action  of  the  atmosphere,  be  rendered 
capable  of  again  yielding  silicate  of  potash 
in  sufficient  quantity  for  the  young  plants. 

The  same  precaution  must  be  observed 
with  regard  to  the  other  inorganic  constitu- 
ents, when  it  is  desired  to  grow  different 
plants  in  succession  on  the  same  soil :  for  a 
successive  growth  of  plants  which  extract 
the  same  component  parts,  must  gradually 
render  it  incapable  of  producing  them. 
Each  of  these  plants  during  its  growth  re- 
turns to  the  soil  a  certain  quantity  of  sub- 
stances containing  carbon,  which  are  gra- 
dually converted  into  humus,  and  are  for  the 
most  part  equivalent  to  as  much  carbon  as 
the  plants  had  formerly  extracted  from  the 
soil  in  a  state  of  carbonic  acid.  But  al- 
though this  is  sufficient  to  bring  many  plants 
to  maturity,  it  is  not  enough  to  furnish  their 
different  organs  with  the  greatest  possible 
supply  of  nourishment.  Now  the  object  of 
agriculture  is  to  produce  either  articles  of 
commerce,  or  food  for  man  and  animals  ; 
but  a  maximum  of  produce  in  plants  is  al- 
ways in  proportion  to  the  quantity  of  nutri- 
ment supplied  to  them  in  the  first  stage  of 
their  developement. 

The  nutriment  of  young  plants  consists 
of  carbonic  acid,  contained  in  the  soil  in  the 
form  of  humus,  and  of  nitrogen  in  the  form 
of  ammonia,  both  of  which  must  be  sup- 
plied to  the  plants,  if  the  desired  purpose  is 
to  be  accomplished.  The  formation  of  am- 
monia cannot  be  effected  on  cultivated  land, 
but  humus  may  be  artificially  produced ;  and 
this  must  be  considered  as  an  important  ob- 
ject in  the  alternation  of  crops,  and  as  the 
second  reason  of  its  peculiar  advantages. 


*  Silica  is  found  in  the  joints  of  bamboos,  in  the 
form  of  small  round  globules,  which  have  received 
the  name  of  Tabasheer,  and  are  distinguished  by 
their  remarkable  optical  properties. 


The  sowing  of  a  field  with  fallow  plants, 
such  as  clover,  rye,  buck-wheat,  &.C.,  and 
the  incorporation  of  plants,  when  nearly  at 
blossom,  with  the  soil,  affect  this  supply  of 
humus  in  so  far,  that  young  plants  subse- 
quently growing  in  it  find,  at  a  certain  pe- 
riod of  their  growth,  a  maximum  of  nu- 
triment, that  is,  matter  in  the  process  of  de- 
cay. 

The  same  end  is  obtained,  but  with  much 
greater  certainty,  when  the  field  is  planted 
with  sainfoin  or  lucerne.*  These  plants  are 
remarkable  on  account  of  the  great  ramifi- 
cation of  their  roots,  and  strong  develope- 
ment of  their  leaves,  and  for  requiring  only 
a  small  quantity  of  inorganic  matter.  Until 
they  reach  a  certain  period  of  their  growth, 
they  retain  all  the  carbonic  acid  and  ammo- 
nia which  may  have  been  conveyed  to  them 
by  rain  and  the  air,  for  that  which  is  not 
absorbed  by  the  soil  is  appropriated  by  the 
leaves ;  they  also  possess  an  extensive  four 
or  six-fold  surface,  capable  of  assimilating 
these  bodies,  and  of  preventing  the  volatili- 
zation of  the  ammonia  from  the  soil,  by 
completely  covering  it  in. 

An  immediate  consequence  of  the  pro- 
duction of  the  green  principle  of  the  leaves, 
and  of  their  remaining  component  parts,  as 
well  as  those  of  the  stem,  is  the  equally 
abundant  excretion  of  organic  matters  into 
the  soil  from  the  roots. 

The  favourable  influence  which  this  ex- 
ercises on  the  land,  by  furnishing  it  with 
matter  capable  of  being  converted  into  hu- 
mus, lasts  for  several  years,  but  barren  spots 
gradually  appear  after  the  lapse  of  some 
time.  Now  it  is  evident  that,  after  from  six 
to  seven  years,  the  ground  must  become  so 
impregnated  with  excrements  that  every 
fibre  of  the  root  will  be  surrounded  with 
them.  As  they  remain  for  some  time  in  a 
soluble  condition,  the  plants  must  absorb 
part  of  them  and  suffer  injurious  effects  in 
consequence,  because  they  are  not  capable 
of  assimilation.  When  such  a  field  is  ob- 
served for  several  years,  it  is  seen  that  the 
barren  spots  are  again  covered  with  vegeta- 
tion, (the  same  plants  being  always  sup- 
posed to  be  grown,)  whilst  new  spots  be- 
come bare  and  apparently  unfruitful,  and  so 
on  alternately.  The  causes  which  produce 
this  alternate  barrenness  and  fertility  in  the 
different  parts  of  the  land  are  evident.  The 
excrements  upon  the  barren  spots  receiving 
no  new  addition,  and  being  subjected  to  the 
influence  of  air  and  moisture,  they  pass  into 
putrefaction,  and  their  injurious  influence 


*  The  alternation  of  crops  with  sainfoin  and  lu- 
cern  is  now  universally  adopted  in  Bingen  and  its 
vicinity,  as  well  as  in  the  Palatinate  ;  the  fields  in 
these  districts  receive  manure  only  once  every 
nine  years.  In  the  first  years  after  the  land  has 
been  manured  turnips  are  sown  upon  it,  in  the 
next  following  years  barley,  with  sainfoin  or  lu- 
cerne ;  in  the  seventh  year  potatoes,  in  the  eighth 
wheat,  in  the  ninth  barley  ;  on  the  tenth  year  it  ia 
manured,  and  then  the  same  rotation  again  takes 
place. 


ON    MANURE. 


59 


ceases.  The  plants  now  find  those  sub- 
stances which  formerly  prevented  their 
growth  removed,  and  in  their  place  meet 
with  humus,  that  is,  vegetable  matter  in  the 
act  of  decay. 

We  can  scarcely  suppose  a  better  means 
of  producing  humus  than  by  the  growth  of 
plants,  the  leaves  of  which  are  food  for  ani- 
mals )  for  they  prepare  the  soil  for  plants  of 
every  other  kind,  but  particularly  for  those 
to  which,  as  to  rape  and  flax,  the, presence 
of  humus  is  the  most  essential  condition  of 
growth. 

The  reasons  why  this  interchange  of  crops- 
is  so  advantageous — the  principles  which 
regulate  this  part  of  agriculture,  are,  there- 
fore, the  artificial  production  of  humus,  and 
the  cultivation  of  different  kinds  of  plants 
upon  the  same  field,  in  such  an  order  of 
succession,  that  each  shall  extract  only  cer- 
tain components  of  the  soil,  whilst  it  leaves 
behind  or  restores  those  which  a  second  or 
third  species  of  plant  may  require  for  its 
growth  and  perfect  developement. 

Now,  although  the  quantity  of  humus  in 
a  soil  may  be  increased  to  a  certain  degree 
by  an  artificial  cultivation,  still,  in  spite  of 
this,  there  cannot  be  the  smallest  doubt  that 
a  soil  must  gradually  lose  those  of  its  con- 
stituents which  are  removed  in  the  seeds, 
roots,  and  leaves  of  the  plants  raised  upon 
it.  The  fertility  of  a  soil  cannot  remain  un- 
impaired, unless  we  replace  in  it  all  those 
substances  of  which  it  has  been  thus  de- 
prived. 

Now  this  is  effected  by  manure. 


CHAPTER  IX. 

OF   MANURE. 

WHEN  it  is  considered  that  every  consti- 
tuent of  the  body  of  man  and  animals  is  de- 
rived from  plants,  and  that  not  a  single 
element  is  generated  by  the  vital  principle, 
it  is  evident  that  all  the  inorganic  constitu- 
ents of  the  animal  organism  must  be  re- 
garded, in  some  respect  or  other,  as  manure. 
During  their  life,  the  inorganic  components 
of  plants  which  are  not  required  by  the  ani- 
mal system,  are  disengaged  from  the  orga- 
nism, in  the  form  of  excrements.  After 
their  death,  their  nitrogen  and  carbon  pass 
into  the  atmosphere  as  ammonia  and  car- 
bonic acid,  the  products  of  their  putrefac- 
tion, and  at  last  nothing  remains  except  the 
phosphate  of  lime  and  other  salts  in  their 
bones.  Now  this  earthy  residue,  of  the  pu- 
trefaction of  animals  must  be  considered,  in 
a  rational  system  of  agriculture,  as  a  power- 
ful manure  for  plants,  because  that  which 
has  been  abstracted  from  a  soil  for  a  series 
of  years  must  be  restored  to  it,  if  the  land 
is  to  be  kept  in  a  permanent  condition  of 
fertility. 

ANIMAL    MANURES. 

We  may  now  inquire  whether  the  excre- 


ments of  animals,  which  are  emplo\cil  as 
manure,  are  all  of  a  like  nature  and  power, 
and  whether  they,  in  every  case,  administer 
to  the  necessities  of  a  plant  by  an  identica 
mode  of  action.  These  points  may  easily 
be  determined  by  ascertaining  the  composi- 
tion of  the  animal  excrements,  because  we 
shall  thus  learn  what  substances  a  soil  really 
receives  by  their  means.  According  to  the 
common  view,  the  action  of  solid  animal 
excrements  depends  on  the  decaying  orga- 
nic matters  which  replace  the  humus,  and 
on  the  presence  of  certain  compounds  of 
nitrogen,  which  are  supposed  to  be  assimi- 
lated by  plants,  and  employed  in  the  pro- 
duction of  gluten  and  other  azotised  sub- 
stances. But  this  view  requires  further 
confirmation  with  respect  to  the  solid  excre- 
ments of  animals,  for  they  contain  so  small 
a  proportion  of  nitrogen,  that  they  cannot 
possibly  by  means  of  it  exercise  any  in- 
fluence upon  vegetation. 

We  may  form  a  tolerably  correct  idea  of 
the  chemical  nature  of  the  animal  excre- 
ment without  further  examination,  by  com- 
paring the  excrements  of  a  dog  with  its 
food.  When  a  dog  is  fed  with  flesh  and 
bones,  both  of  which  consist  in  great  part 
of  organic  substances  containing  nitrogen,  a 
moist  white  excrement  is  produced,  which 
crumbles  gradually  to  a  dry  powder  in  the 
air.  This  excrement  consists  of  the  phos- 
phate of  lime  of  the.  bones,  and  contains 
scarcely  J^-Q  part  of  its  weight  of  foreign 
organic  substances.  The  whole  process  ot 
nutrition  in  an  animal  consists  in  the  pro- 
gressive extraction  of  all  the  nitrogen  from 
the  food,  so  that  the  quantity  of  this  element 
found  in  the  excrements  must  always  be 
less  than  that  contained  in  the  nutriment. 
The  analysis  of  the  excrements  of  a  horse 
by  Macaire  and  Marcet  proves  this  fact  com- 
pletely. The  portion  of  excrements  sub- 
jected to  analysis  was  collected  whilst  fresh, 
and  dried  in  vacuo  over  sulphuric  acid ;  100 
parts  of  it  (corresponding  to  from  350  to 
400  parts  of  the  dung  before  being  dried) 
contained  0.8  of  nitrogen.  Now  every  one 
who  has  had  experience  in  this  kind  of  ana- 
lysis is  aware  that  a  quantity  under  one  per 
cent,  cannot  be  determined  with  accuracy. 
We  should,  therefore,  be  estimating  its  pro- 
portion at  a  maximum,  were  we  to  consider 
it  as  equal  to  one-half  per  cent.  It  is  cer- 
tain, however,  that  these  excrements  are  not 
entirely  free  frorn  nitrogen,  for  they  emit 
ammonia  when  digested  with  caustic  potash. 

The  excrements  of  a  cow,  on  combustion 
with  oxide  of  copper,  yielded  a  gas  which 
contained  one  vol.  of  nitrogen  gas,  and  26.30 
vol.  of  carbonic  acid. 

100  parts  of  fresh  excrements  contained 


Nitrogen 
Carbon     . 
Hydrogen 
Oxygen    . 
Ashes    . 
Water 


.  0.506 
.  6.204 
.  0824 

.  4.818 
..  1.748 
.  85.900 

100.000 


60 


AGRICULTURAL  CHEMISTRY. 


Now,  according  to  the  analysis  of  Bous-  |  smell.     100 
singault,  which  merits  the   greatest   confi-   horse   bein 
dence,  hay  contains  one  per  cent,  of  nitro- 
gen ;   consequently  in  the  25  Ibs.    of  hay 
which  a  cow  consumes  daily,  £  of  a  Ib.  of 
nitrogen  must  have  been  assimilated.    This 


quantity  of  nitrogen  entering  into  the  com- 
position of  muscular  fibre  would  yield  8*3 
Ibs.  of  flesh  in  its  natural  condition.*  The 
daily  increase  in  size  of  a  cow  is,  however, 
much  less  than  this  quantity.  We  find  that 
the  nitrogen.,  apparently  deficient,  is  actually 
contained  in  the  milk  and  urine  of  the  ani- 
mal. The  urine  of  a  milch-cow  contains 
less  nitrogen  than  that  of  one  which  does 
not  yield  milk ;  and  as  long  as  a  cow  yields 
a  plentiful  supply  of  milk,  it  cannot  be  fat- 
tened. We  must  search  for  the  nitrogen  of 
the  food  assimilated,  not  in  the  solid,  but  in 
the  liquid  excrements.  The  influence  which 
the  former  exercise  on  the  growth  of  vege- 
tables does  not  depend  upon  the  quantity  of 
nitrogen  which  they  contain.  For  if  this 
were  the  case,  hay  should  possess  the  same 
influence ;  that  is,  from  20  to  25  Ibs.  ought 
to  have  the  same  power  as  100  Ibs.  of  fresh 
cow-dung.  But  this  is  quite  opposed  to  all 
experience. 

Which  then  are  the  substances  in  the  ex- 
crements of  the  cow  and  horse  which  exert 
an  influence  on  vegetation  ? 

When  horse-dung  is  treated  with  water, 
a  portion  of  it  to  the  amount  of  3  or  3^  per 
cent,  is  dissolved,  and  the  water  is  coloured 
yellow.  The  solution  is  found  to  contain 
phosphate  of  magnesia,  and  salts  of  soda, 
besides  small  quantities  of  organic  matters.f 
The  portion  of  the  dung  undissolved  by  the 
water  yields  to  alcohol  a  resinous  substance 
possessing  all  the  characters  of  gall  which 
has  undergone  some  change;  while  the 
residue  possesses  the  properties  of  saw-dust, 
from  which  all  soluble  matter  has  been  ex- 
tracted by  water,  and  burns  without  any 


*  100  Ibs.  of  flesh  contain  on  an  average  15'86 
of  muscular  fibre :  18  parts  of  nitrogen  are  con- 
tained in  100  parts  of  the  latter. 

t  Dr.  C.  T.  Jackson  in  his  "Geological  and 
Agricultural  Survey  of  Rhode  Island,"  (page  205.) 
gives  the  following  analysis  of  horse-dung : — 50C 
grains,  dried  at  a  heat  a  little  above  that  of  boiling 
water,  lost  357  grains  of  water.  The  dry  mass 
weighing  143  grains  was  burned,  and  left  8*5  grains 
of  ashes,  of  which  4'80  grains  were  soluble  in 


dilute  nitric  acid,  and  3 '20  insoluble, 
being  analysed,  gave 

Silica    .... 

Phosphate  of  lime 

Carbonate  of  lime 

Phosphate  of  magnesia  and  soda 


The  ashes 

3-2 
0-4 
1-5 

2-9 

8-0 

It  consists,  then,  of  the  following  ingredients  :— 
Water  ....     357'0 

Vegetable  fibre  and  animal  matter         135-0 
Silica    .  ...        3'2 

Phosphate  of  lime  .  .  0'4 

Carbonate  of  lime       .  .  .        T5 

Phosphate  oi  magnesia  and  soda  .  29 

500-0 


parts  of  the  fresh  dung  of  a 
dried  at  100°  C.  (212°  F.) 
eave  from  25  to  30  or  31  parts  of  solid  sub- 
stances, and  contained,  accordingly,  from  69 
:o  75  parts  of  water.  From  the  dried  ex- 
crements, we  obtain,  by  incineration,  vari- 


able quantities  of  salts  and  earthy  matters, 
according  to  the  nature  of  the  food  which 
las  been  taken  by  the  animal.  Macaire  and 
Vlarcet  found  27  per  cent,  in  the  dung  ana- 
ysed  by  them;  I  obtained  only  10  per  cent, 
rom  that  of  a  horse  fed  with  chopped  straw, 
oats,  and  hay.  It  results  then  that  with 
>om  3600  to  4000  Ibs.  of  fresh  horse-dung, 
corresponding  to  100  Ibs.  of  dry  dung,  we 
place  on  the  land  from  2484  to  3000  Ibs.  of 
water,  and  from  730  to  900  Ibs.  of  vegetable 
matter  and  altered  gall,  and  also  from  100 
to  270  Ibs.  of  salt  and  other  inorganic  sub- 
stances. 

The  latter,  are  evidently  the  substances  to 
which  our  attention  should  be  directed,  for 
they  are  the  same  which  formed  the  compo- 
nent parts  of  the  hay,  straw,  and  oats  with 
which  the  horse  was  fed.  Their  principal 
constituents  are  the  phosphates  of  lime  and 
magnesia,  carbonate  of  lime  and  silicate  of 
potash;  the  first  three  of  these  preponde- 
rated in  the  corn,  the  latter  in  hay. 

Thus  in  1000  Ibs.  of  horse-dung,  we  pre- 
sent to  a  field  the  inorganic  substances  con- 
tained in  6000  Ibs.  of  hay,  or  8300  Ibs.  oi 
oats  (oats  containing  3'1  per  cent,  ashes  ac- 
cording to  De  Saussure.)  This  is  sufficient 
to  supply  l£  crop  of  wheat  with  potash  and 
phosphates. 

The  excrements  of  cows,*  black  cattle, 
and  sheep,  contain  phosphate  of  lime,  com- 
mon  salt,  and  silicate  of  lime,  the  weight  of 
which  varies  from  9  to  28  per  cent.,  accord- 
ing to  the  fodder  which  the  animal  receives ; 
the  fresh  excrements  of  the  cow  contain 
from  86  to  90  per  cent,  of  water. 

Human  faeces  have  been  subjected  to  an 
exact  analysis  by  Berzelius.  When  fresh 
they  contain,  beside  f  of  their  weight  oi 
water,  nitrogen  in  very  variable  quantity, 
namely,  in  the  minimum  1|,  in  the  maxi- 


*  It  has  been  formerly  stated  (page  41)  that  all 
the  potash  contained  in  the  food  of  a  cow  is  again 
discharged  in  its  excrements.  The  same  also 
takes  place  with  the  other  inorganic  constituents 
of  food,  either  when  they  are  not  adapted  for  as- 
similation, or  when  present  in  superabundant 
quantities.  The  value  of  manure  may  thus  be 
artificially  increased.  We  lately  saw,  for  ex- 
ample, some  cow-dung,  sent  by  a  farmer,  who 
wished  to  ascertain  the  cause  of  its  increased 
value.  He  had  formerly  employed  this  manure 
for  his  land,  but  with  so  little  advantage  that  he 
found  it  more  profitable  to  dry  it,  and  use  it  as 
fuel.  On  inquiry,  it  was  found,  that  his  cows  had 
been  fed  upon  oil-cake.  This  species  of  food 
is  particularly  rich  in  phosphates.  More  of  these 
salts  being  present  than  were  requisite  for  the 
purpose  of  assimilation,  they  were  removed  from 
the  system  in  the  form  of  excrementitious  matter, 
and  in  a  condition  adapted  for  the  uses  of  plants. 
The  fact  that  particular  kinds  of  food  enrich  or 
impoverish  the  manure  obtained  from  the  cattle  fed 
upon  them,  has  repeatedly  been  observed. — Ei> 


OF    MANUttE. 


61 


mum  5  per  cent.  In  all  cases,  however 
they  were  richer  in  this  element  than  thj 
excrements  of  other  animals.  Berzeliu 
obtained  by  the  incineration  of  100  parts  oj 
dried  excrements,  15  parts  of  ashes,  whic] 
were  principally  composed  of  the  phosphate, 
of  lime  and  magnesia. 

The  following  quantitative  organic  ana 
lysis  has  recently  been  executed  for  the  pur 
pose  of  ascertaining  the  proportion  of  carbon 
nitrogen,  and  inorganic  matter  contained  in 
faeces,  in  comparison  with  the  food  taken.* 
(Playfair.) 

Carbon  .  .  .  45'24 

Hydrogen  .  .          6 '88 

Nitrogen  (average)  •  .     4'00 

Oxygen     .  .  .        30'30 

Ashes  .  .  .   13-58 

The  inorganic  matter  contained  in  the 
excrements  analyzed  is  nearly  two  per  cent, 
less  than  that  found  by  Berzelius;  but  the 
proportion  always  varies,  according  to  the 
nature  of  the  food. 

It  is  quite  certain  that  the  vegetable  con- 
stituents of  the  excrements  with  which  we 
manure  our  fields  cannot  be  entirely  without 
influence  upon  the  growth  of  the  crops  on 
them,  for  they  will  decay,  and  thus  furnish 
carbonic  acid  to  the  young  plants.  But  it 
cannot  be  imagined  that  their  influence  is 
very  great,  when  it  is  considered  that  a  good 
soil  is  manured  only  once  every  six  or  seven 
years,  or  once  every  eleven  or  twelve  years, 
when  sainfoin  or  lucerne  has  been  raised  on 
it,  that  the  quantity  of  carbon  thus  given  to 
the  land  corresponds  to  only  5-8  per  cent,  of 
what  is  removed  in  the  form  of  herbs,  straw, 
and  grain;  and  farther  that  the  rain-water 
received  by  a  soil  contains  much  more  car- 
bon in  the  form  of  carbonic  acid  than  these 
vegetable  constituents  of  the  manure. 

The  peculiar  action  then,  of  the  solid  ex- 
crements is  limited  to  their  inorganic  con- 
stituents, which  thus  restore  to  a  soil  that 
which  is  removed  in  the  form  of  corn,  roots, 
or  grain.  When  we  manure  land  with  the 
dung  of  the  cow  or  sheep,  we  supply  it 
with  silicate  of  potash  and  some  salts  of 
phosphoric  acid.  In  human  faeces  we  give 
it  the  phosphates  of  lime  and  magnesia; 
and  in  those  of  the  horse,  phosphate  of 
magnesia,  and  silicate  of  potash.  In  the 
straw  which  has  served  as  litter,  we  add  a 
farther  quantity  of  silicate  of  potash  and 
phosphates ;  which,  if  the  straw  be  putre- 
fied, are  in  exactly  the  same  condition  in 
which  they  were  before  being  assimilated. 

It  is  evident,  therefore,  that  the  soil  of  a 
field  will  alter  but  little,  if  we  collect  and 
distribute  the  dung  carefully  ;  a  certain  por- 
tion of  the  posphates,  however,  must  be  lost 
every  year,  being  removed  from  the  land 

*  The  details  of  the  analysis  are  as  follows : — 
2-356  grammes  left  0'320  gramme  ashes  after 
incineration  ;  these  consisted  of  the  phosphate  of 
lime  and  magnesia.  0'352  gramme  yielded,  on 
combustion  with  oxide  of  copper,  0'576  gram, 
carbonic  acid,  and  0'218  gram,  water.  (L.  P.) 


with  the  corn  and  cattle,  and  this  portion 
will  accumulate  in  the  neighbourhood  of 
large  towns.  The  loss  thus  suffered  must 
be  compensated  for  in  a  well-managed  farm, 
and  this  is  partly  done  by  allowing  the  fields 
to  lie  in  grass.  In  Germany,  it  is  considered 
that  for  every  100  acres  of  corn-land,  there 
must,  in  order  to  effect  a  profitable  cultiva- 
tion, be  20  acres  of  pasture-land,  which  pro- 
duce annually,  on  an  average,  500  Ibs.  of 
hay.  Now,  assuming  that  the  ashes  of  the 
excrements  of  the  animals  fed  with  this  hay 
amount  to  6.82  per  cent.,  then  341  Ibs.  of 
the  silicate  of  lime  and  posphates  of  magne- 
sia and  lime  must  be  yielded  by  these  excre- 
ments, and  will  in  a  certain  measure  com- 
pensate for  the  loss  which  the  corn-land  had 
sustained. 

The  absolute  loss  in  the  salts  of  phospho- 
ric acid,  which  are  not  again  replaced,  is 
spread  over  so  great  an  extent  of  surface, 
that  it  scarcely  deserves  to  be  taken  ac- 
count of.  But  the  loss  of  phosphates  is 
again  replaced  in  the  pastures  by  the  ashes 
of  the  wood  used  in  our  houses  for  fuel. 

We  could  keep  our  fields  in  a  constant 
state  of  fertility  by  replacing  every  year  as 
mach  as  we  remove  from  them  in  the  form 
of  produce;  but  an  increase  of  fertility,  and 
consequent  increase  of  crop,  can  only  be 
obtained  when  we  add  more  to  them  than 
we  take  away.  It  will  be  found,  that  of  two 
fields  placed  under  conditions  otherwise 
similar,  the  one  will  be  most  fruitful  upon 
which  the  plants  are  enabled  to  appropriate 
more  easily  and  in  greater  abundance  those 
contents  of  the  soil  which  are  essential  to 
their  growth  and  developement. 

From  the  foregoing  remarks  it  will  readily  • 
inferred,  that  for  animal  excrements, 
other  substances  containing  their  essential 
constituents  may  be  substituted.  In  Flan- 
ders, the  yearly  loss  of  the  necessaiy  matters 
'n  the  soil  is  completely  restored  by  covering 
he  fields  with  ashes  of  wood  'or  bones, 
which  may  or  may  not  have  been  lixiviated^ 
and  of  which  the  greatest  part  consists  ot 
he  phosphates  of  lime  and  magnesia.  The 
jreat  importance  of  manuring  with  ashes 
las  been  long  recognised  by  agriculturists 
as  the  result  of  experience.  So  great  a 
value,  indeed,  is  attached  to  this  material  in 
he  vicinity  of  Marburg  and  in  the  Wette- 
•au,*  that  it  is  transported  as  a  manure 
rom  the  distance  of  18  or  24  miles.  Its  use 
will  be  at  once  perceived,  when  it  is  con- 
idered  that  the  ashes,  after  having  been 
cashed  with  water,  contain  silicate  of  pot 
sh  exactly  in  the  same  proportion  as  in 
traw  HO  Si  O  3  -f  K  O.,)  and  that  their 
>nly  other  constituents  are  salts  of  phospho- 
ic  acid. 

But  ashes  obtained  from  various  kinds  of 
rees  are  of  very  unequal  value  for  this  pur- 
ose;  those  from  oak-wood  are  the  least, 


*  Two  well-known  agricultural  districts  ;  the 
rst  in  Hesse-Cassel,  the  second  in  Hesse-Darm- 
tadt. 

F 


62 


AGRICULTURAL   CHEMISTRY. 


and  those  from  beech  the  most  serviceable. 
The  asiies  of  oak-wood  contain  only  traces 
of  phosphates,  those  of  beech  the  fifth  part 
of  their  weight,  and  those  of  the  pine  and  fir 
from  9  to  15  per  cent.  The  ashes  of  pines 
from  Norway  contain  an  exceedingly  small 
quantity  of  phosphates,  namely,  only  1-8 
per  cent,  of  phosphoric  acid.  (Berthier.) 

With  every  100  Ibs.  of  the  lixiviated  ashes 
of  the  beech  which  we  spread  over  a  soil, 
we  furnish  as  much  phosphates  as  460  Ibs. 
of  fresh  human  excrements  could  yield. 
Again,  according  to  the  analysis  of  De 
Saussure,  100  parts  of  the  ashes  of  the  grain 
of  wheat  contain  32  parts  of  soluble,  and 
44-5  of  insoluble  phosphates,  in  all  76'5 
parts.  Now  the  ashes  of  wheat  straw  con- 
tain 11-5  per  cent,  of  the  same  salts ;  hence 
with  every  100  Ibs.  of  the  ashes  of  the  beech, 
we  supply  a  field  with  phosphoric  acid  suf- 
ficient for  the  production  of  3820  Ibs.  of 
straw  (its  ashes  being  calculated  at  4-3  per 
cent.,  De  Saussure,)  or  for  15-18000  Ibs.  of 
corn,  the  ashes  of  which  amount,  according 
to  De  Saussnre,  to  1-3  per  cent. 

Bone  manure  possesses  a  still  greater  im- 
portance in  this  respect.  The  primary 
sources  from  which  the  bones  of  animals 
are  derived  are,  the  hay,  straw,  or  other 
substances  which  they  take  as  food.  Now, 
if  we  admit  that  bones  contain  55  per 
cent,  of  the  phosphates  of  lime  and  magne- 
sia fBerzelius,)  and  that  hay  contains  as 
much  of  them  as  wheat-straw,  it  will  follow 
that  8  Ibs.  of  bones  contain  as  much  phos- 
phate of  lime  as  1000  Ibs.  of  hay  or  wheat- 
straw,  and  2  Ibs.  of  it  as  much  as  1000  Ibs. 
of  the  grain  of  wheat  or  oats.  These  num- 
bers express  pretty  nearly  the  quantity  of 
phosphates  which  a  soil  yields  annually  on 
the  growth  of  hay  and  corn.  Now  the  ma- 
nure of  an  acre  of  land  with  40  Ibs.  of  bone 
dust  is  sufficient  to  supply  three  crops  of 
wheat,  clover,  potatoes,  turnips,  &c.,  with 
phosphates.  But  the  form  in  which  they 
are  restored  to  a  soil  does  not  appear  to  be  a 
matter  of  indifference.  For  the  more  finely 
the  bones  are  reduced  to  powder,  and  the 
more  intimately  they  are  mixed  with  the 
soil,  the  more  easily  are  they  assimilated. 
The  most  easy  and  practical  mode  of  effect- 
ing their  division  is  to  pour  over  the  bones, 
in  a  state  of  fine  powder,  half  of  their  weight 
of  sulphuric  acid  diluted  with  three  or  four 
parts  of  water,  and  after  they  have  been  di  - 
gested  for  some  time,  to  add  one  hundred 
parts  of  water,  and  sprinkle  this  mixture 
over  the  field  before  the  plough.  In  a  few 
seconds,  the  free  acids  unite  with  the  bases 
contained  in  the  earth,  and  a  neutral  salt  is 
formed  in  a  very  fine  state  of  division.  Ex- 
periments instituted  on  a  soil  formed  from 
grauwacke,  for  the  purpose  of  ascertaining 
the  action  of  manure  thus  prepared,  have 
distinctly  shown  that  neither  corn,,  nor 
kitchen-garden  plants,  surfer  injurious  ef- 
fects in  consequence,  but  that  on  the  con- 
trary they  thrive  with  much  more  vigour. 

It  has  also  been  found  that  bones  act 


|  more  speedily  and  efficaciously  after  oeing 
'  boiled.     This   is  probably  owing  to  the  re- 
moval of  fatty  matter,  the  presence  of  which 
impedes  the  putrefaction  of  the  gelatin  con- 
tained in  them. 

In  the  manufactories  of  glue,  many  hun- 
dred tons  of  a  solution  of  phosphates  in  mu- 
riatic acid  are  yearly  thrown  away  as  being 
useless.  It  would  be  important  to  examine 
whether  this  solution  might  not  be  substi- 
tuted for  the  bones.  The  free  acid  wo  jld 
combine  with  the  alkalies  in  the  soil,  espe- 
cially with  the  lime,  and  a  soluble  salt 
would  thus  be  produced,  which  is  known 
to  possess  a  favourable  action  upon  the 
growth  of  plants.  This  salt,  muriate  of 
lime  (or  chloride  of  calcium,)  is  one  of 
those  compounds  which  attracts  water  from 
the  atmosphere  with  great  avidity,  and  in 
dry  lands  might  advantageously  supply  the 
place  of  gypsum  in  decomposing  carbonate 
of  ammonia,  with  the  formation  of  sal-am 
moniac  and  carbonate  of  lime.  A  solution 
of  bones  in  muriatic  acid  placed  on  land  in 
autumn  or  in  winter  would,  therefore,  not 
only  restore  a  necessary  constituent  of  the 
soil,  and  attract  moisture  to  it,  but  would 
also  give  it  the  power  to  retain  all  the  am- 
monia which  fell  upon  it  dissolved  in  the 
rain  during  the  period  of  six  months.* 

The  ashes  of  brown  coal  and  peat  often 
contain  silicate  of  potash,  so  that  it  is  evi- 
dent that  these  might  completely  replace  one 
of  the  principal  constituents  of  the  dung 
of  the  cow  and  horse,  and  they  contain  also 
some  phosphates.  Indeed  they  are  much 
esteemed  in  the  Wetterau  as  manure  for 
meadows  and  moist  land. 

It  is  of  much  importance  to  the  agricul 
turist  that  he  should  not  deceive  himself  re- 
specting the  causes  which  give  the- peculiar 
action  to  the  substances  just  mentioned.  It 
is  known  that  they  possess  a  very  favour- 
able influence  on  vegetation  ;  and  it  is  like- 
wise certain  that  the  cause  of  this  is  their 
containing  a  body,  which,  independently  of 
the  influence  which  it  exerts  by  virtue  of  its 
form,  porosity,  and  capability  of  attracting 
and  retaining  moisture,  also  assists  in  main- 
taining the  vital  processes  in  plants.  If  it  be 
treated  as  an  unfathomable  mystery,  the  na- 
ture of  this  aid  will  never  be  known. 

In  medicine,  for  many  centuries,  the  mode 
of  action  of  all  remedies  was  supposed  to  be 
concealed  by  the  mystic  veil  of  Isis,  but 
now  these  secrets  have  been  explained  in  a 


*  Immense  quantities  of  bran  are  used  in  all 
print-works,  for  the  purpose  of  clearing  printed 
goods.  After  having  served  this  purpose,  it  is 
thrown  away.  But  the  insoluble  part  of  bran 
contains  much  phosphates  of  magnesia  and  soda  ; 
it  would,  therefore,  be  useful  to  preserve  it  as  a 
manure.  This  has  been  done  for  some  years  in  a 
farm  with  which  I  am  connected,  and  its  value  as 
a  manure  has  been  found  so  great  that  it  is  much 
preferred  to  cow-dung.  In  some  works  this  waste 
bran  is  heaped  up  into  little  hillocks,  which  might 
be  disposed  of  as  a  manure,  instead  of  being  an 
annoyance  on  account  of  the  space  which  it  occu- 
pies.— ED. 


OF   MANURE. 


63 


very  simple  manner.  An  unpoetical  hand 
has  pointed  out  the  cause  of  the  wonderful 
and  apparently  inexplicable  healing  virtues 
of  the  springs  in  Savoy,  by  which  the  inha- 
bitants cured  their  goitre ;  it  was  shown  that 
they  contain  small  quantities  of  iodine.  In 
burnt  sponges  used  for  the  same  purpose, 
the  same  element  was  also  detected.  The 
extraordinary  efficacy  of  Peruvian  bark  was 
found  to  depend  on  a  small  quantity  of  a 
crystalline  body  existing  in  it,  viz.  quinine ; 
and  the  causes  of  the  various  effects  of 
opium  were  detected  in  as  many  different 
ingredients  of  that  drug. 

Calico-printers  used  for  a  long  time  the 
solid  excrements  of  the  cow,  in  order  to 
brighten  and  fasten  colours  on  cotton  goods ; 
this  material  appeared  quite  indispensable, 
and  its  action  was  ascribed  to  a  latent  prin- 
ciple which  it  had  obtained  from  the  living 
organism.  But  since  its  action  was  known 
to  depend  on  the  phosphates  contained  in  it, 
it  has  been  completely  replaced  by  a  mix- 
ture of  salts,  in  which  the  principal  con- 
stituents are  the  phosphates  of  soda  and 
lime.* 

Now  all  such  actions  depend  on  a  definite 
cause,  by  ascertaining  which  we  place  the 
actions  themselves  at  our  command. 

It  must  be  admitted  as  a  principle  of  agri- 
culture, that  those  substances  which  have 
been  removed  from  a  soil  must  be  com- 
pletely restored  to  it,  and  whether  this  resto- 
ration be  effected  by  means  of  excrements, 
ashes,  or  bones,  is  in  a  great  measure  a  mat- 
ter of  indifference.  A  time  will  come  when 
fields  will  be  manured  with  a  solution  of  glass, 
(silicate  of  potash,)  with  the  ashes  of  burnt 
straw,  and  with  salts  of  phosphoric  acid, 
prepared  in  chemical  manufactories,  exactly 
as  at  present  medicines  are  given  for  fever 
and  goitre. 

There  are  some  plants  which  require 
numus,  and  do  not  restore  it  to  the  soil  by 
their  excrements ;  whilst  others  can  do  with- 
out it  altogether,  and  add  humus  to  a  soil 
which  contains  it  in  small  quantity.  Hence 
a  rational  system  of  agriculture  would  em- 
ploy all  the  humus  at  command  for  the  sup- 
ply of  the  former,  and  not  expend  any  of  it 
for  the  latter;  and  would  in  fact  make  use 
of  them  for  supplying  the  others  with 
humus. 

•  We  have  now  considered  all  that  is  requi- 
site in  a  soil,  in  order  to  furnish  its  plants 
with  the  materials  necessary  for  the  forma- 
tion of  the  woody  fibre,  the  grain,  the  roots, 
and  the  stem,  and  now  proceed  to  the  con- 
sideration of  the  most  important  object  of 
agriculture,  viz.  the  production  of  nitrogen 
in  a  form  capable  of  assimilation — the  pro- 
duction, therefore,  of  substances  containing 

*  This  mixture  of  salts  is  sold  to  calico-printers 
in  large  quantities  under  the  name  of  "  dung  sub- 
stitute." It  would  be  well  worth  experiment  to 
try  its  effects  as  a  manure  upon  land.  Its  cost  is 
3d.  or  4d.  per  pound,  and  is  not,  therefore,  dearer 
than  nitrate  of  soda,  which  is  now  so  extensively 
used.— ED. 


this  element.  The  leaves,  which  nourish 
the  woody  matter,  the  roots,  from  which  the 
leaves  are  formed,  and  which  prepare  the 
substances  for  entering  into  the  composition 
of  the  fruit,  and,  in  short,  every  part  of  the 
organism  of  a  plant,  contain  azotised  matter 
in  very  varying  proportions,  but  the  seeds 
and  roots  are  always  particularly  rich  in 
them. 

Let  us  now  examine  in  what  manner  the 
greatest  possible  production  of  substances 
containing  nitrogen  can  be  effected.  Nature, 
by  means  of  the  atmosphere,  furnishes  ni- 
trogen to  a  plant  in  quantity  sufficient  for 
its  normal  growth.  Now  its  growth  must 
be  considered  as  normal,  when  it  produces 
a  single  seed  capable  of  reproducing  the 
same  plant  in  the  following  year.  Such  a 
normal  condition  would  suffice  for  the  ex- 
istence of  plants,  and  prevent  their  extinc- 
tion, but  they  do  not  exist  for  themselves 
alone;  the  greater  number  of  animals  de- 
pend on  the  vegetable  world  for  food,  and 
by  a  wise  adjustment  of  nature,  plants  have 
the  remarkable  power  of  converting,  to  a 
certain  degree,  all  the  nitrogen  offered  to 
them  into  nutriment  for  animals. 

We  may  furnish  a  plant  with  carbonic 
acid,  and  all  the  materials  which  it  may  re- 
quire; we  may  supply  it  with  humus  in  the 
most  abundant  quantity;  but  it  will  not  at- 
tain complete  developement  unless  nitrogen 
is  also  afforded  to  it;  an  herb  will  be  formed, 
but  no  grain ;  even  sugar  and  starch  may 
be  produced,  but  no  gluten. 

But  when  we  give  a  plant  nitrogen  in 
considerable  quantity,  we  enable  it  to  attract 
with  greater  energy  from  the  atmosphere 
the  carbon  which  is  necessary  for  its  nutri- 
tion, when  that  in  the  soil  is  not  sufficient; 
we  afford  to  it  a  means  of  fixing  the  carbon* 
of  the  atmosphere  in  its  organism. 

We  cannot  ascribe  much  of  the  power 
of  the  excrements  of  black  cattle,  sheep, 
and  horses,  to  the  nitrogen  which  they  con- 
tain, for  its  quantity  is  too  minute.  But  that 
contained  in  the  faeces  of  man  is  proportion- 
ably  much  greater,  although  by  no  means 
constant.  In  the  faeces  of  the  inhabitants  of 
towns,  for  example,  who  feed  on  animal 
matter,  there  is  much  more  of  this  consti- 
tuent than  in  those  of  peasants,  or  of  such 
people  as  reside  in  the  country.  The  faeces 
of  those  who  live  principally  on  bread  and 
potatoes  are  similar  in  composition  and  pro- 
perties to  those  of  animals. 

All  excrements  have  in  this  respect  a  very 
variable  and  relative  value.  Thus  those  of 
black  cattle  and  horses  are  of  great  use  on 
soils  consisting  of  lime  and  sand,  which 
contain  no  silicate  of  potash  and  phosphates ; 
whilst  their  value  is  much  less  when  applied 
to  soils  formed  of  argillaceous  earth,  basalt, 
granite,  porphyry,  clinkstone,  and  even 
mountain-limestone,  because  all  these  con- 
tain potash  in  considerable  quantity.  In 
such  soils  human  excrements  are  extremely 
beneficial,  and  increase  their  fertility  in  a 
remarkable  degree ;  they  are,  of  course,  as 


64 


AGRICULTURAL   CHEMISTRY. 


advantageous  for  other  soils  also;  but  for 
tne  manure  of  those  first  mentioned,  the  ex- 
crements of  other  animals  are  quite  indis- 
pensable. 

OF  URINE. 

We  possess  only  one  other  natural  source 
of  manure  which  acts  by  its  nitrogen,  be- 
sides the  faeces  of  animals, — namely,  the 
urine  of  man  and  animals. 

Urine  is  employed  as  manure  either  in 
the  liquid  state,  or  with  the  fasces  which 
are  impregnated  with  it.  It  is  the  urine 
contained  in  them  which  gives  to  the  solid 
faeces  the  property  of  emitting  ammonia, — a 
property  which  they  themselves  possess  only 
in  a  very  slight  degree. 

When  we  examine  what  substances  we 
add  to  a  soil  by  supplying  it  with  urine,  we 
find  that  this  liquid  contains  in  solution  am- 
moriiacal  salts,  uric  acid  (a  substance  con- 
taining a  large  quantity  of  nitrogen,)  and 
salts  of  phosphoric  acid. 

According  to  Berzelius  1000  parts  of  hu- 
man urine  contain: — 

Urea 30'10 

Free  Lactic  acid,  Lactate  of  Ammonia,  and 

animal  matter  not  separable  from  them  17*14 

Uric  acid 1  00 

Mucus  of  the  bladder   -                 »        •  0'32 

Sulphate  of  Potash           ....  3'71 

Sulphate  of  Soda          ....  3'16 

Phosphate  of  Soda 2'94 

Phosphate  of  Ammonia                 •        •  1'65 

Chloride  of  Sodium          ....  4-45 

Muriate  of  Ammonia    -        -        -        .  150 

Phosphates  of  Magnesia  and  Lime  -        •  TOO 

Silicious  earth 0'03 

Water 933'00 

100000 

If  we  subtract  from  the  above  the  urea, 
lactate  of  ammonia,  free  lactic  acid,  uric 
acid,  the  phosphate  and  muriate  of  ammo- 
nia; 1  per  cent,  of  solid  matter  remains, 
consisting  of  inorganic  salts,  which  must 
possess  the  same  action  when  brought  on  a 
field,  whether  they  are  dissolved  in  water  or 
in  urine.  Hence  the  powerful  influence  of 
urine  must  depend  upon  its  other  ingredients, 
namely,  the  urea  and  ammoniacal  salts. 
The  urea  in  human  urine  exists  partly  as 
lactate  of  urea,  and  partly  in  a  free  state. 
(Henry.)  Now  when  urine  is  allowed  to 
putrefy  spontaneously,  that  is,  to  pass  into 
that  state  in  which  it  is  used  as  manure,  all 
the  urea  in  combination  with  lactic  acid  is 
converted  into  lactate  of  ammonia,  and  that 
which  was  free,  into  volatile  carbonate  of 
ammonia. 

In  dung- reservoirs  well  constructed  and 
protected  from  evaporation,  this  carbonate 
of  ammonia  is  retained  in  the  state  of  solu- 
tion, and  when  the  putrefied  urine  is  spread 
over  the  land,  a  part  of  the  ammonia  will 
escape  with  the  water  which  evaporates, 
but  another  portion  will  be  absorbed  by  the 
soil,  if  it  contains  either  alumina  or  iron; 
but  in  general  only  the  muriate,  phosphate, 
and  lactate  of  ammonia  remain  in  the 


ground.  It  is  these  alone,  therefore,  which 
enable  the  soil  to  exercise  a  direct  influence 
on  plants  during  the  progress  of  their  growth, 
and  not  a  particle  of  them  escapes  being  ab- 
sorbed by  the  roots. 

On  account  of  the  formation  of  this  car- 
bonate of  ammonia  the  urine  becomes  alka- 
line, although  it  is  acid  in  its  natural  state. 
When  it  is  lost  by  being  volatilized  in  the 
air,  which  happens  in  most  cases,  the  loss 
suffered  is  nearly  equal  to  one  half  of  the 
weight  of  the  urine  employed,  so  that  if  we 
fix  it,  that  is,  if  we  deprive  it  of  its  volatility, 
we  increase  its  action  two-fold.  The  exist- 
ence of  carbonate  of  ammonia  in  putrefied 
urine  long  since  suggested  the  manufacture 
of  sal-ammoniac  from  this  material.  When 
the  latter  salt  possessed  a  high  price,  this 
manufacture  was  even  carried  on  by  the 
farmer.  For  this  purpose  the  liquid  obtained 
from  dunghills  was  placed  in  vessels  of  iron, 
and  subjected  to  distillation;  the  product  of 
this  distillation  was  converted  into  muriate 
of  ammonia  by  the  common  method.  (De- 
machy.)  But  it  is  evident  that  such  a 
thoughtless  proceeding  must  be  wholly  re- 
linquished, since  the  nitrogen  of  100  Ibs.  of 
sal-ammoniac  (which  contains  26  parts  of 
nitrogen)  is  equal  to  the  quantity  of  nitrogen 
contained  in  1200  Ibs.  of  the  grain  of  wheat, 
1480  Ibs.  of  that  of  barley,  or  2755  Ibs.  of 
hay.  (Boussingault.) 

The  carbonate  of  ammonia  formed  by  the 
putrefaction  of  urine,  can  be  fixed  or  de- 
prived of  its  volatility  in  many  ways. 

If  a  field  be  strewed  with  gypsum,  and 
then  with  putrefied  urine  or  the  drainings 
of  dunghills,  all  the  carbonate  of  ammonia 
will  be  converted  into  the  sulphate  which 
will  remain  in  the  soil. 

But  there  are  still  simpler  means  of  effect- 
ing this  purpose  ; — gypsum,  chloride  of  cal- 
cium, sulphuric  or  muriatic  acid,  and  super- 
phosphate of  lime,  are  all  substances  of  a 
very  low  price,  and  completely  neutralise 
the  urine,  converting  its  ammonia  into  salts 
which  possess  no  volatility. 

If  a  basin,  filled  with  concentrated  mu- 
riatic acid,  is  placed  in  a  common  necessary, 
so  that  its  surface  is  in  free  communication 
with  the  vapours  which  rise  from  below,  it 
becomes  filled  after  a  few  days  with  crystals 
of  muriate  of  ammonia.  The  ammonia,  the 
presence  of  which  the  organs  of  smell  amply 
testify,  combines  with  the  muriatic  acid  and 
loses  entirely  its  volatility,  and  thick  clouds 
or  fumes  of  the  salt  newly  formed  hang  over 
the  basin.  In  stables  the  same  may  be  seen. 
The  ammonia  that  escapes  in  this  manner 
is  not  only  entirely  lost,  as  far  as  our  vegeta- 
tion is  concerned,  but  it  works  also  a  slow, 
though  not  less  certain  destruction  of  the 
walls  of  the  building.  For  when  in  contact 
with  the  lime  of  the  mortar,  it  is  converted 
into  nitric  acid,  which  gradually  dissolves 
the  lime.  The  injury  thus  done  to  a  build- 
ing by  the  formation  of  the  soluble  nitrates, 
has  received  (in  Germany)  a  special  name 
— salpeterfrass. 


OF    MANURE. 


65 


The  ammonia  emitted  from  stables  and 
necessaries  is  always  in  combination  with 
carbonic  acid.  Carbonate  of  ammonia  and 
sulphate  of  lime  (gypsum)  cannot  be  brought 
together  at  common  temperatures,  without 
mutual  decomposition.  The  ammonia  enters 
into  combination  with  the  sulphuric  acid, 
and  the  carbonic  acid  with  the  lime,  form- 
ing compounds  which  are  not  volatile,  and 
consequently  destitute  of  all  smell.  Now, 
if  we  strew  the  floors  of  our  stables,  from 
lime  to  time,  with  common  gypsum,  they 
vill  lose  all  their  offensive  smell,  and  none 
jf  the  ammonia  which  forms  can  be  lost, 
uut  will  be  retained  in  a  condition  service- 
able as  manure. 

With  the  exception  of  urea,  uric  acid 
contains  more  nitrogen  than  any  other  sub- 
stance generated  by  the  living  organism;  it 
is  soluble  in  water,  and  can  be  thus  absorbed 
by  the  roots  of  plants,  and  its  nitrogen  as- 
similated in  the  form  of  ammonia,  and  of 
the  oxalate,  hydrocyanate,  or  carborfate  of 
ammonia. 

It  would  be  extremely  interesting  to  study 
the  transformations  which  uric  acid  suffers 
in  a  living  plant.  For  the  purpose  of  experi- 
ment, the  plant  should  be  made  to  grow  in 
charcoal  powder  previously  heated  to  red- 
ness, and  then  mixed  with  pure  uric  acid. 
The  examination  of  the  juice  of  the  plant, 
or  of  the  component  parts  of  the  seed  or 
fruit,  would  be  a  means  of  easily  detecting 
the  differences. 

NIGHT-SOIL. 

IN  respect  to  the  quantity  of  nitrogen  con- 
tained in  excrements,  100  parts  of  the  urine 
of  a  healthy  man  are  equal  to  1300  parts  of 
the  fresh  dung  of  a  horse,  according  to  the 
analyses  of  Macaire  and  Marcet,  and  to  600 
parts  of  those  of  a  cow.  Hence  it  is  evident 
that  it  would  be  of  much  importance  to 
agriculture  if  none  of  the  human  urine  were 
lost.  The  powerful  effects  of  urine  as  a 
manure  are  well  known  in  Flanders,*  but 
they  are  considered  invaluable  by  the  Chi- 
nese, who  are  the  oldest  agricultural  people 
we  know.  Indeed  so  much  value  is  attached 
to  the  influence  of  human  excrements  by 
these  people,  that  laws  of  the  state  forbid 
that  any  of  them  should  be  thrown  away, 
and  reservoirs  are  placed  in  every  house,  in 
which  they  are  collected  with  the  greatest 
care.  No  other  kind  of  manure  is  used  for 
their  corn-fields.f 


*  See  the  article  "  On  the  Agriculture  of  the 
Netherlands,"  Journ.  Royal  Agri.  Soc.,  vol.  ii. 
part  1,  page  43,  for  much  interesting  information 
on  this  subject. 

t  Davis,  in  his  History  of  China,  states  that 
every  subs'ance  convertible  into  manure  is  dili- 
gently husbanded.  "  The  cakes  that  remain  after 
the  expression  of  their  vegetable  oils,  horns  and 
hoofs  reduced  to  powder,  together  with  soot  and 
ashes,  and  the  ^contents  of  common  sewers,  are 
much  used.  The  plaster  of  old  kitchens,  which 
in  China  have  no  chimneys  but  an  opening  at  the 
top,  is  much  valued  ;  so  that  they  will  sometimes 
put  a  new  plaster  on  a  kitchen  for  the  sake  of  the 
9 


China  is  the  birth-place  of  the  ex  peri- 
mental  art;  the  incessant  striving  after  ex- 
periments has  conducted  the  Chinese  a  thou  • 
sand  years  since  to  discoveries,  which  have 
been  the  envy  and  admiration  of  Europeans 
for  centuries,  especially  in  regard  to  dying 
and  painting,  and  to  the  manufactures  of 
porcelain,  silk,  and  colours  for  painters. 
These  we  were  long  unable  to  imitate,  and 
yet  they  were  discovered  by  them  without 
the  assistance  of  scientific  principles  ;  for  in 
the  books  of  the  Chinese  we  find  recipes 
and  directions  for  use,  but  never  explana 
tions  of  processes. 


old."  The  ammonia  contained  in  the  fuel  forma 
nitrate  of  lime  with  the  lime  in  the  mortar.  "  All 
sorts  of  hair  are  used  as  a  manure,  and  barbers' 
shavings  are  carefully  appropriated  to  that  pur- 
pose. The  annual  produce  must  be  considerable 
in  a  country  where  some  hundred  millions  of 
heads  are  kept  constantly  shaved.  Dung  of  all 
animals,  but  more  especially  night-soil,  is  esteemed 
above  all  others.  Being  sometimes  formed  into 
cakes,  it  is  dried  in  the  sun,  and  in  this  state  be- 
comes an  object  of  sale  to  farmers,  who  dilute  it 
previous  to  use.  They  construct  large  cisterns 
or  pits,  lined  with  lime  plaster,  as  well  as  earthen 
tubs,  sunk  into  the  ground,  with  straw  over  them 
to  prevent  evaporation,  in  which  all  kinds  of  vege- 
tables and  animal  refuse  are  collected.  ThesQ 
being  diluted  with  a  sufficient  quantity  of  liquid, 
are  left  to  undergo  the  putrefactive  fermentation, 
and  then  applied  to  the  land.  In  the  case  of  every 
thing  except  rice,  the  Chinese  seem  to  manure  the 
plant  itself  rather  than  the  soil,  supplying  it  co- 
piously with  their  liquid  preparation." 

"  The  Chinese  husbandman,"  observes  Sir  G. 
Staunton,  (Embassy,  vol.  ii.,)  "  always  steeps  the 
seeds  he  intends  to  sow  in  liquid  manure,  until 
they  swell,  and  germination  begins  to  appear, 
which  experience  has  taught  him  will  have  the 
effect  of  hastening  the  growth  of  plants,  as  well 
as  of  defending  them  against  the  insects  hidden 
in  the  ground  in  which  the  seeds  are  sown.  To 
the  roots  of  plants  and  fruit-trees,  the  Chinese 
farmer  applies  liquid  manure  likewise." 

Lastly,  we  extract  the  following  from  a  com- 
munication to  Professor  Webster,  of  Harvard 
College,  United  States :-—"  Human  urine  is,  if 
possible,  more  husbanded  by  the  Chinese  than 
night-soil  for  manure ;  every  farm,  or  patch  of 
land  for  cultivation,  has  a  tank,  where  all  sub- 
stances convertible  into  manure  are  carefully  de- 
posited, the  whole  made  liquid  by  adding  urine 
in  the  proportion  required,  and  invariably  applied 
in  that  state."  This  is  exactly  the  process  fol- 
lowed in  the  Netherlands.  See  Outlines  ofFlem» 
ish  Husbandry,  page  22. 

"The  business  of  collecting  urine  and  night- 
soil  employs  an  immense  number  of  persons,  who 
deposit  tubs  in  every  house  in  the  cities  for  the 
reception  of  the  urine  of  the  inmates,  which  ^es- 
sels  are  removed  daily,  with  as  much  care  as  our 
farmers  remove  their  honey  from  the  hives." 

When  we  consider  the  immense  value  of  night- 
soil  as  a  manure,  it  is  quite  astounding  that  so 
little  attention  is  paid  to  preserve  it.  The  quantity 
is  immense  which  is  carried  down  by  the  drains 
in  London  to  the  River  Thames,  serving  no  other- 
purpose  than  to  pollute  its  waters.  It  has  been 
shown,  by  a  very  simple  calculation,  that  the 
value  of  the  manure  thus  lost  amounts  annually 
to  several  millions  of  pounds  sterling.  A  sub-' 
stance,  which  by  its  putrefaction  generates  mias- 
mata, may,  by  artificial  means,  be  rendered  totally 
inoffensive,  inodorous,  and  transportable,  and  yet 
prejudice  prevents  these  means  being  resorted  to*' 
— ED. 

F  2 


66 


AGRICULTURAL   CHEMISTRY. 


Half  a  century  sufficed  to  Europeans  not 
««ly  to  equal  but  to  surpass  the  Chinese  in 
the  arts  and  manufactures,  and  this  was 
owing  merely  to  the  application  of  correct 
principles  deduced  from  the  study  of  che- 
mistry. But  how  infinitely  inferior  is  the 
agriculture  of  Europe  to  that  of  China ! 
The  Chinese  are  the  most  admirable  gar- 
deners and  trainers  of  plants,  for  each  of 
which  they  understand  how  to  prepare  and 
apply  the  best-adapted  manure.  The  agri- 
culture of  their  country  is  the  most  perfect 
in  the  world;  and  there,  where  the  climate 
in  the  most  fertile  districts  differs  little  from 
the  European,  very  little  value  is  attached 
to  the  excrements  of  animals.  With  us, 
thick  books  are  written,  but  no  experiments 
instituted ;  the  quantity  of  manure  consumed 
by  this  and  that  plant  is  expressed  in  hun- 
dredth parts,  and  yet  we  know  not  what 
manure  is  ! 

If  we  admit  that  the  liquid  and  solid  ex- 
crements of  man  amount  on  an  average  to 
l£  Ib.  daily,  (f-  Ib.  of  urine  and  £  Ib.  faeces,) 
and  that  both  taken  together  contain  3  per 
cent,  of  nitrogen,  then  in  one  year  they  will 
amount  to  547  IDS.,  which  contain  16-41  Ibs. 
of  nitrogen,  a  quantity  sufficient  to  yield  the 
nitrogen  of  800  Ibs.  of  wheat,  rye,  oats,  or 
of  900  Ibs.  of  barley.  (Boussingault.) 

This  is  much  more  than  is  necessary  to 
add  to  an  acre  of  land  in  order  to  obtain, 
with  the  assistance  of  the  nitrogen  absorbed 
from  the  atmosphere,  the  richest  possible 
crop  every  year.  Every  town  and  farm 
might  thus  supply  itself  with  the  manure, 
which,  besides  containing  the  most  nitrogen, 
contains  also  the  most  phosphates;  and  if 
rotation  of  the  crops  were  adopted,  they 
would  be  most  abundant.  By  using,  at  the 
same  time,  bones  and  the  lixiviated  ashes 
of  wood,  the  excrements  of  animals  might 
be  completely  dispensed  with. 

When  human  excrements  are  treated  in 
a  proper  manner,  so  as  to  remove  the  mois- 
ture which  they  contain  without  permitting 
the  escape  of  ammonia,  they  may  be  put 
into  such  a  form  as  will  allow  them  to  be 
transported  even  to  great  distances. 

This  is  already  attempted  in  many  towns, 
and  the  preparation  of  night-soil  for  trans- 
portation constitutes  not  an  unimportant 
branch  of  industry.  But  the  manner  in 
which  this  is  done  is  the  most  injudicious 
which  could  be  conceived.  In  Paris,  for 
example,  the  excrements  are  preserved  in 
the  houses  in  open  casks,  from  which  they 
are  collected  and  placed  in  deep  pits  at 
Montfaucon,  but  are  not  sold  until  they  have 
attained  a  certain  degree  of  dryness  by  eva- 
poration in  the  air.  But  whilst  lying  in  the 
receptacles  appropriated  for  them  in  the 
houses,  the  greatest  part  of  their  urea  is 
converted  into  carbonate  of  ammonia  ;  lac- 
tate  and  phosphate  of  ammonia  are  also 
formed,  and  the  vegetable  matters  contained 
in  them  putrefy ;  all  their  sulphates  are  de- 
composed, whilst  their  sulphur  forms  sul- 
phuretted hydrogen  and  hydro-sulphate  of 


ammonia.  The  mass,  when  dried  by  ex 
posure  to  the  air,  has  lost  more  than  half  of 
the  nitrogen  which  the  excrements  originally 
contained ;  for  the  ammonia  escapes  into 
the  atmosphere  along  with  the  water  which 
evaporates ;  and  the  residue  now  consists 
principally  of  phosphate  of  lime,  with  phos- 
phate and  lactate  of  ammonia,  and  small 
quantities  of  urate  of  magnesia  and  fatty 
matter.  Nevertheless  it  is  still  a  very  pow- 
erful manure,  but  its  value  as  such  would 
be  twice  or  four  times  as  great,  if  the  excre- 
ments before  being  dried  were  neutralised 
with  a  cheap  mineral  acid. 

In  other  manufactories  of  manure  the 
night-soil,  whilst  still  soft,  is  mixed  with  the 
ashes  of  wood,  or  with  earth,  both  of  which 
substances  contain  a  large  quantity  01  caus- 
tic lime,  by  means  of  which  a  complete  ex- 
pulsion of  all  its  ammonia  is  effected,  and  it 
is  completely  deprived  of  smell.  But  such 
a  residue  applied  as  manure  can  act  only  by 
the  pliosphates  which  it  still  contains,  for 
all  the  ammoniacal  salts  have  been  decom- 
posed and  their  ammonia  expelled. 

The  preparation  of  night-soil  is  now  car- 
ried on  in  London  to  a  considerable  extent. 
Owin^  to  the  variable  nature  of  the  climate, 
artificial  means  are  employed  in  its  desicca- 
tion. The  night-soil,  after  being  subjected 
to  one  or  other  of  the  modes  of  treatment 
described  below,  is  placed  upon  iron  plates 
heated  by  means  of  furnaces. 

As  soon  as  the  night-soil  is  coAected,  it  is 
placed  in  large  broad  trenches,  until  a  suffi- 
cient quantity  is  accumulated  for  the  pur- 
poses of  the  manufacturer.  But  here  it 
undergoes  the  same  process  of  putrefaction 
to  which  allusion  has  been  made,  and  ac- 
quires a  peculiarly  offensive  smell  from  the 
evolution  of  sulphuretted  hydrogen  and 
other  gases,  which  are  observed  to  escape. 
Unless  some  means  be  employed,  at  this 
stage  of  the  process,  to  retain  the  ammonia, 
it  escapes  into  the  atmosphere  in  the  form 
i  of  a  carbonate.  Various  methods  have  been 
proposed  to  effect  this  purpose.  Some  manu- 
facturers mix  the  night-soil  with  chloride  of 
lime,  and  evaporate  off  the  water  by  the  aid 
of  heat.  This  possesses  the  advantage  of 
depriving  the  excrements  of  smell,  and  at 
the  same  time  partially  fixes  the  ammonia 
which  would  otherwise  escape.  Chloride 
of  lime  always  contains  a  considerable  ex- 
cess of  lime ;  hence  part  of  the  ammonia 
contained  in  the  night-soil  is  expelled  by 
means  of  it.  , 

More  simple  and  economical  methods 
might  be  employed.  A  patent,  which  has 
been  taken  out  for  the  preparation  of  this 
useful  manure,  states  in  its  specification, 
that  the  night-soil  is  to  be  mixed  with  cal- 
I  cined  mud  and  finely-divided  charcoal.  By 
this  means,  the  smell  is  completely  and  in- 
stantaneously removed,  and  the  ammonia 
!  retained  by  virtue  of  the  affinity  which  alu- 
I  mma  and  charcoal  exert  for  that  compound. 
!  This  plan  is  both  simple  and  efficacious,  bur 
,the  ammonia  is  apt  to  be  expelled  by  the 


OF   MANURE. 


67 


application  of  the  heat  employed  in  drying 
the  manure.  The  addition  of  a  cheap  mine- 
ral acid  to  the  night-soil,,  before  admixture 
with  these  ingredients,  would  materially 
improve  both  of  the  above  processes. 

It  would  no  doubt  be  highly  advantageous 
in  the  preparation  of  manures,  to  prepare 
them  so  that  they  contained  all  the  ingredi- 
ents necessary  for  the  supply  of  the  plants 
to  which  they  are  applied.  But  these  will 
of  course  vary  according  to  the  nature  of 
the  soils  and  plants  for  which  they  are  in- 
tended. Thus  bones,  soap-boilers'  waste, 
nitrate  of  soda,  and  ashes  of  wood,  will 
often  be  found  to  form  advantageous  addi- 
tions. Sulphate  of  magnesia  (Epsom  salts) 
would,  in  most  cases,  form  an  invaluable 
ingredient  in  prepared  night-soil.  (See  Sup- 
plementary Chapter  on  Soils.)  The  pro- 
ducts of  the  decomposition  proceeding  from 
the  action  of  this  salt  upon  night-soil  are, 
sulphate  of  ammonia,  phosphate  of  mag- 
nesia, and  the  double  phosphate  of  magnesia 
and  ammonia.  Now  all  these  salts  exert  a 
very  favourable  influence  upon  vegetation, 
and  the  phosphate  of  magnesia  is,  in  many 
cases,  perfectly  indispensable  to  the  growth 
and  developement  of  certain  plants.  This 
suggestion  is  well  worthy  of  the  attention 
of  the  farmer. 

Perhaps  the  best  and  most  practical  me- 
thod of  fixing  the  ammoniacal  salts  of  urine 
and  night-soil,  is  to  mix  them  with  the 
ashes  of  peat  or  coal.  When  the  latter  are 
employed,  care  must  be  taken  to  select  such 
as  are  of  a  porous,  earthy  consistence.  The 
ashes  both  of  peat  and  coal  contair  in  gene- 
ral magnesia ;  hence  their  value  as  an  in- 
gredient of  prepared  night-soil.  When 
magnesia  is  not  present,  it  will  be  necessary 
to  add  some  magnesian  limestone  or  Epsom 
salts.  The  night-soil  should  be  mixed  tho- 
roughly with  the  ashes,  and  exposed  to  the 
air  to  dry.  The  disagreeable  smell  is  thus 
quickly  removed,  and  a  pulverulent  manure 
obtained,  which  can  be  applied  to  the  fields 
with  facility. 

Animal  charcoal,  which  has  served  for 
the  discoloration  of  sugar,  possesses  the  pro- 
perty of  removing  the  offensive  smell  of 
night-soil,  and  is  of  itself  an  admirable  ma- 
nure. In  cases  where  it  can  be  procured 
with  facility,  it  will  be  found  to  add  to  the 
efficacy  of  the  latter. 

GUANO. 

The  sterile  soils  of  the  South  American 
coas\  are  manured  with  a  substance  called 
guano,  consisting  of  urate  of  ammonia  and 
other  ammoniacal  salts,  by  the  use  of  which 
a  luxuriant  vegetation  and  the  richest  crops 
are  obtained.  Guano  has  lately  been  im- 
ported in  considerable  quantity  into  Liver- 
pool and  several  other  English  ports,  and  is 
now  experimentally  employed  as  a  manure 
by  English  agriculturists.  A  consideration 
of  its  composition  and  mode  of  action  can- 
not, therefore,  fail  to  be  acceptable. 


I  Much  speculation  has  arisen  as  to  the 
I  true  origin  of  guano,*  but  the  most  certain 
proof  is  now  afforded,  that  it  has  been. pro- 
duced by  the  accumulation  of  the  excre- 
ments of  innumerable  sea-fowl  which  inhabit 
the  islands  upon  which  it  is  found.  Meyen, 
the  latest  writer  upon  this  subject,  com- 
pletely coincides  with  this  opinion ;  for  he 
saysf — "  Their  number  is  Legion ;  they 
completely  cloud  the  sun,  when  they  rise 
from  their  resting-place  in  the  morning  in 
flocks  of  miles  in  length."  Yet,  notwith- 
standing their  great  number,  thousands  of 
years  must  have  elapsed,  before  the  excre- 
ments could  have  accumulated  to  such  a 
thickness  as  they  possess  at  present.  Guano 
has  been  used  by  the  Peruvians  as  a  manure 
since  the  twelfth  century  ;  and  its  value  was 
considered  so  inestimable,  that  the  govern- 
ment of  the  Incas  issued  a  decree,  by  which 
capital  punishment  was  inflicted  upon  any 
person  found  destroying  the  fowl  on  the 
Guano  islands.  Overseers  were  also  ap- 
pointed over  each  province,  for  the  purpose 
of  insuring  them  further  protection.  Under 
this  state  of  things,  the  accumulation  of  the 
excrements  may  have  well  taken  place.  All 
these  regulations  are,  however,  now  aban- 
doned.J  Rivero  states  that  the  annual  con- 
sumption of  guano  for  the  purposes  of  agri- 
culture amounts  to  40,000  fanegas.  The 
increase  of  crops  obtained  by  the  use  of 
guano  is  very  remarkable.  According  to 
the  same  authority,  the  crop  of  potatoes  is 
increased  45  times  by  means  of  it,  and  that 
of  maize  35  times.  The  manner  of  apply- 
ing the  manure  is  singular.  Thus  in  Arica, 
where  so  much  pepper  (  Capsicum  baccatum) 
is  cultivated,  each  plant  is  manured  three 
times  :  first  upon  the  appearance  of  the  roots, 
second  upon  that  of  the  leaves,  and  lastly 
upon  the  formation  of  the  fruit.  (Humboldt.) 
From  this  it  will  be  observed,  that  the  Pe- 
ruvians follow  the  plan  of  the  Chinese,  in 
manuring  the  plant  rather  than  the  soil. 
The  composition  of  guano  points  out  how 
admirably  it  is  fitted  for  a  manure ;  for  not 
only  does  it  contain  ammoniacal  salts  in 
abundance,  but  also  those  inorganic  consti- 
tuents which  are  indispensable  for  the  de- 
velopement of  plants. 

The  most  recent  analysis  is  that  of  Volc- 
kel,  who  found  it  to  consist  of 

Urate  of  Ammonia    .        .        .        •  .        9.0 

Oxalate  of  Ammonia        .        .        .  10.6 

Oxalate  of  Lime        .        .        •  7.0 

Phosphate  of  Ammonia    .        .        .  6.0 

Phosphate  of  Magnesia  and  Ammonia  2.6 

Sulphate  of  Potash            ...  5.5 

Sulphate  of  Soda       ....  3.8 

Sal-ammoniac                    .        ,        .  4.2 

Phosphate  of  Lime 14.3 

Clay  and  Sand                           :        .  .        4.7 

*  Much  of  the  information  regarding  Guano 
here  given  is  extracted  from  a  paper  in  Liebig'g 
Annalen,  xxxvii.  3,  291. 

t  Reise  urn  die  Erde,  B.  i.  S.  434. 

t  Garcilaso,  Ilistoria  de  los  Yncat,  vol.  i 
p.  134. 


68 


AGRICULTURAL   CHEMISTRY. 


Organic  substances  not  estimated,  con-" 
taining  12  per  cent,  of  matter  insolu- 
ble in  water.  Soluable  Salts  of  Iron 
in  small  quantity.  Water- 


—67.7 


32.3 


100.0 

It  will  be  observed  from  the  above  analy- 
sis, that  urea  does  not  enter  into  the  compo- 
sition of  guano.  The  uric  acid  of  the  ex- 
crements must  have  been  decomposed  into 
oxalic  acid  and  ammonia.  The  soluble  sub- 
stances contained,  in  guano  amount  to  half 
its  weight.  It  is  singular  that  we  do  not 
find  nitrates  amongst  the  ingredients  which 
compose  it.  Guano  possesses  a  urinous 
smell,  precisely  similar  to  that  perceived  on 
the  evaporation  of  urine.  The  experiments 
upon  the  efficacy  of  this  manure  in  Eng- 
land have  not  yet  been  sufficiently  multi- 
plied to  enable  us  to  judge  whether  or  not 
its  virtues  have  been  overrated. 

The  corn-fields  in  China  receive  no  other 
manure  than  human  excrements.  But  we 
cover  our  fields  every  year  with  the  seeds  of 
weeds,  which  from  their  nature  and  form 
pass  undigested  along  with  the  excrements 
through  animals,  without  being  deprived  of 
their  power  of  germination,  and  yet  it  is 
considered  surprising  that  where  they  have 
once  flourished,  they  cannot  again  be  ex- 
pelled by  all  our  endeavours  :  we  think  it 
very  astonishing,  while  we  really  sow  them 
ourselves  every  year.  A  famous  botanist, 
attached  to  the  Dutch  embassy  to  China, 
could  scarcely  find  a  single  plant  on  the 
corn-fields  of  the  Chinese,  except  the  corn 
itself.* 

The  urine  of  horses  contains  less  nitrogen 
and  phosphates  than  that  of  man.  Accord- 
ing to  Fourcroy  and  Vauquelin  it  contains 
only  five  per  cent,  of  solid  matter,  and  in 
that  quantity  only  0.7  of  urea;  whilst  100 
parts  of  the  urine  of  man  contain  more  than 
four  times  as  much. 

The  urine  of  a  cow  is  particularly  rich 
in  salts  of  potash ;  but  according  to  Rouelle 
and  Brande,  it  is  almost  destitute  of  salts  of 
soda.  The  urine  of  swine  contains  a  large 
quantity  of  the  phosphate  of  magnesia  and 
ammonia ;  and  hence  it  is  that  concretions 
of  this  salt  are  so  frequently  found  in  the 
urinary  bladders  of  these  animals. 

It  is  evident  that  if  we  place  the  solid  or 
liquid  excrements  of  man  or  the  liquid  ex- 
crements of  animals  on  our  land,  in  equal 
proportion  to  the  quantity  of  nitrogen  re- 
moved from  it  in  the  form  of  plants,  the 
sum  of  this  element  in  the  soil  must  increase 
every  year ;  for  to  the  quantity  which  we 
thus  supply,  another  portion  is  added  from 
the  atmosphere.  The  nitrogen  which  we 
export  as  corn  and  cattle,  and  which  is  thus 
absorbed  by  large  towns,  serves  only  to  be- 
nefit other  farms,  if  we  do  not  replace  it.  A 
farm  which  possesses  no  pastures,  and  not 
fields  sufficient  for  the  cultivation  of  fodder, 


*  Ingenhouss  on  the  Nutrition  of  Plants,  page 
i«9  /German  edition., 


!  requires  manure  containing  nitrogen  to  be 
imported  from  elsewhere,  if  it  is  desired  to 
produce  a  full  crop.  In  large  farms,  the  an- 
nual expenditure  of  nitrogen  is  completely 
replaced  by  means  of  the  pastures. 

The  only  absolute  loss  of  nitrogen,  there- 
fore, is  limited  to  the  quantity  which  man 
carries  with  him  to  his  grave ;  but  this  at 
the  utmost  cannot  amount  to  more  than  3 
Ibs.  for  every  individual,  and  is  being  col- 
lected during  his  whole  life.  Nor  is  this 
quantity  lost  to  plants,  for  it  escapes  into 
the  atmosphere  as  ammonia  during  the  pu- 
trefaction and  decay  of  the  body. 

A  high  degree  of  culture  requires  an  in- 
creased supply  of  manure.  With  the  abun- 
dance of  the  manure,  the  produce  in  corn 
and  cattle  will  augment,  but  must  diminish 
with  its  deficiency. 

From  the  preceding  remarks  it  must  be 
evident,  that  the  greatest  value  should  be  at- 
tached to  the  liquid  excrements  of  man  and 
animals,  when  a  manure  is  desired  which 
shall  supply  nitrogen  to  the  soil.  The 
greatest  part  of  a  superabundant  crop,  or, 
in  other  words,  the  increase  of  growth 
which  is  in  our  power,  can  be  obtained  ex 
clusively  by  their  means. 

When  it  is  considered  that  with  every 
pound  of  ammonia  which  evaporates  a  loss 
of  60  Ibs.  of  corn  is  sustained,  and  that 
with  every  pound  of  urine  a  pound  of  wheat 
might  be  produced,  the  indifference  with 
which  these  liquid  excrements  are  regarded 
is  quite  incomprehensible.  In  most  place? 
only  the  solid  excrements  impregnated  with 
the  liquid  are  used,  and  the  dunghills  con- 
taining them  are  protected  neither  from  eva- 
poration nor  from  rain.  The  solid  excre- 
ments contain  the  insoluble,  the  liquid  all 
the  soluble  phosphates,  and  the  latter  con- 
tain likewise  all  the  potash  which  existed  as 
organic  salts  in  the  plants  consumed  by  the 
animals. 

Fresh  bones,  wool,  hair,  hoofs,  and  horn, 
are  manures  containing  nitrogen  as  well  as 
phosphates,  and  are  consequently  fit  to  aid 
the  process  of  vegetable  life.  All  animal 
matter  is  fitted  for  the  same  purpose. 
Butchers'  offal,  such  as  the  blood  and  intes-v 
tines  of  animals,  form  a  most  powerful  ma- 
nure. It  is  in  general  necessary  to  dilute 
such  manure  by  admixture  with  other  kinds 
less  powerful  in  their  action. 

One  hundred  parts  of  dry  bones  contain 
from  32  to  33  per  cent,  of  dry  gelatine ;  now 
supposing  this  to  contain  the  same  quantity 
of  nitrogen  as  animal  glue,  viz.,  5.28  per 
cent.,  then  100  parts  of  bones  must  be  con- 
sidered as  equivalent  to  250  parts  of  human 
urine. 

Bones  may  be  preserved  unchanged  for 
thousands  of  years,  in  dry  or  even  in  moist 
soils,  provided  the  excess  of  rain  is  prevent- 
ed; as  is  exemplified  by  the  bones  of  an- 
tediluvian animals  found  in  loam  or  gyp- 
sum, the  interior  parts  being  protected  by 
the  exterior  from  the  action  of  water.  But 
they  become  warm  when  reduced  to  a  flue 


OF   MANURE. 


69 


powder,  and  moistened  bones  generate  heat 
and  enter  into  putrefaction ;  the  gelatine 
which  they  contain  is  decomposed,  and  its 
nitrogen  converted  into  carbonate  of  ammo- 
nia and  other  ammoniacal  salts,  which  are 
retained  in  a  great  measure  by  the  powder 
itself.  (Bones  burnt  till  quite  white,  and  re- 
cently heated  to  redness,  absorb  7.5  times 
their  volume  of  pure  ammoniacal  gas.) 

ARTIFICIAL    MANURES. 

WE  have  now  examined  the  action  of  the 
animal  or  natural  manures  upon  plants;  but 
it  is  evident  that  if  artificial  manures  con- 
tain the  same  constituents,  they  will  exer- 
cise a  similar  action  upon  the  plants  to 
which  they  are  applied.  We  shall  only 
notice  here  one  or  two  of  those  principally 
employed. 

Since  it  has  been  ascertained  that  animal 
manures  act  (as  far  as  the  formation  of  or- 
ganic matter  is  concerned^)  only  by  the  am- 
monia which  they  contain,  attention  has 
been  devoted  by  chemists  to  discover  a 
more  economical  means  of  presenting  this 
ammonia  to  plants.  The  water  which  dis- 
tils from  the  retorts  in  the  preparation  of 
coal  gas  is  strongly  charged  with  this  alkali, 
but  is  at  the  same  time  mixed  with  tar  and 
other  empyreumatic  impurities.  It  has  been 
customary  to  allow  the  tarry  matter  to  sub- 
side, and  decant  off  the  clear,  supernatant 
liquor.  This  liquor,  being  diluted  to  such 
a  degree  as  to  be  tasteless,  is  applied  as  a 
manure  to  the  field. 

Now,  the  ammoniacal  liquor  of  the  gas- 
works contains  the  ammonia  in  the  form  of 
carbonate  and  hydro-sulphate  of  ammonia 
(sulphuret  of  ammonium).  The  latter  com- 
pound is  a  deadly  poison  to  vegetables,  nor 
can  we  conceive  that  by  dilmion  its  proper- 
ties can  be  changed.  The  carbonate  of 
ammonia  is  volatile,  and  escapes  into  the  at- 
mosphere. To  obviate  this  latter  inconveni- 
ence and  render  it  more  transportable,  it  has 
been  proposed  to  convert  the  carbonate  into 
the  sulphate,  by  means  of  gypsum.*  But 
this  does  not  remove  the  hydro-sulphate. 
A  more  simple  and  efficacious  method  is  to 
add  a  solution  of  sulphate  of  iron  (the  green 
vitriol  of  the  shops)  to  the  liquor,  until  no 
further  precipitation  ensues.  Sulphuret 
and  carbonate  of  iron  are  thus  formed,  and 
the  whole  of  the  ammonia  enters  into  com- 
bination with  the  sulphuric  acid,  and  forms 
sulphate  of  ammonia.  Care  must  be  taken 
to  avoid  too  great  an  excess  of  sulphate  of 
iron ;  and  the  liquor  thus  prepared  should 
be  freely  exposed  to  the  air  to  promote  the 
oxidation. 

The  liquor  still,  however,  contains  em- 
pvreumatic  matters,  which  are  injurious  to 
plants.  These  may  be  removed  by  evapo- 
rating the  liquor  to  dryness,  and  heating  the 
residue  to  incipient  redness.  By  this  means 
they  are  rendered  insoluble,  and  the  sul- 

*  Three  Lectures  on  Agile ultuiu,  by  Dr.  Dau- 
beny,  page  87 


phaie  of  ammonia  is  not  affected,  unless  the 
heat  has  been  carried  too  far.  The  liquor 
properly  diluted  has  been  found  very  advan- 
tageous, even  without  the  removal  of  the 
empyreumatic  matter. 

Nitrate  of  soda  has  lately  engaged  much 
attention,  and  is  supposed  to  exert  its  fa- 
vourable action  upon  vegetation  by  yielding 
nitrogen  to  those  of  their  constituents  which 
contain  it.  The  experiments  which  have 
hitherto  been  instituted  with  this  manure  do 
not  warrant  us  in  concluding  with"  positive 
certainty  that  it  is  the  nitrogen  alone  to 
which  it  owes  its  efficacy,  but  they  certainly 
render  this  a  plausible  explanation  of  its 
virtues.  Thus  Mr.  Pusey,  the-  late  able 
president  of  the  Royal  Agricultural  Society, 
has  shown,  that  the  same  effects  are  pro- 
duced by  putrefied  urine,  soot,  gas-liquor, 
and  nitrate  of  soda.*  Now  the  three  for- 
mer act  by  virtue  of  the  ammonia  which 
enters  into  their  composition.  The  usual 
effects  produced  by  these  and  nitrate  of  soda 
are  to  increase  the  intensity  of  the  green, 
colouring  matter,  to  augment  the  quantity 
of  straw,  but  to  produce  a  light  grain.  Mr. 
Hyettf  has  communicated  the  results  of  an 
analysis  of  two  samples  of  wheat  grown 
under  similar  circumstances,  one  of  which 
had  been  treated  with  nitre,  the  other  not. 
The  former  contained  23-25  per  cent.  01 
gluten,  and  l-375  of  albumen;  the  latter 
only  19  per  cent,  of  gluten,  and  O62  of  al- 
bumen. Here  the  azotised  matters  appear 
to  have  considerably  increased  in  quantity. 
There  is  nothing  opposed  to  the  supposition 
that  nitric  acid  may  be  decomposed  by 
plants,  and  its  nitrogen  assimilated.  We 
find  that  vegetables  possess  the  power  of 
decomposing  carbonic  acid,  and  of  appro- 
priating its  carbon  for  their  own  use.  Now 
this  acid  is  infinitely  more  difficult  to  decom- 
pose than  nitric  acid.  But  there  are  other 
circumstances  which  oppose  the  adoption 
of  the  view  that  nitrate  of  soda  acts  by  vir- 
tue of  the  nitrogen  which  enters  into  its 
composition.  Were  this  the  case,  the  ac- 
tion should  be  more  uniform  than  it  has 
hitherto  been  found  to  be.  On  some  soils 
the  salt  does  not  possess  the  smallest  influ- 
ence ;  whilst  on  others  it  affords  great  bene- 
fit. We  can  only  furnish  an  explanation  ot 
this  seeming  caprice  by  a  reference  to  the 
chemical  composition  or  the  soil  upon  which 
it  is  applied.  If  the  advantages  attending 
the  application  of  nitrate  of  soda  are  due  to 
the  alkaline  base  which  it  contains,  then  it 
is  evident  that  this  manure  can  be  of  small 
value  on  soils  containing  a  quantity  of  alka- 
lies sufficient  for  the  purposes  of  the  plants 
grown  upon  them ;  whilst,  on  the  -other 
hand,  such  as  are  deficient  in  these  must  ex- 
perience benefit  through  its  means. J  In 


*  Journal  of  the  Royal  Agricultural  Society, 
vol.  ii.,  p.  123. 

t  Journal  of  the  Royal  Agricultural  Society, 
vol.  ii.,  p.  143. 

I  General  Sir  Howard  Elphinstone  informs  m« 
that  he  found  carbonate  of  soda  (soda  ash)  an  ex 


70 


AGRICULTURAL   CHEMISTRY 


certain  cases  in  which  nitrate  of  soda  has  I  ent  families  of  plants  are  distinguished  by 
failed,  nitrate  of  potash  (common  saltpetre)  '  containing  certain  acids,  differing  very  mucn 
has  been  very  successful.  Analyses  of ,  in  composition;  and  further,  that  these  acids 


wheat  grown  with  nitrate  of  soda  and  nitrate 
of  potash  would  be  of  interest,  in  order  to 
determine  whether  a  mutual  substitution  of 
their  respective  bases  is  effected.  It  is  to  be 
hoped  that  future  experiments  will  throw 
more  light  upon  the  action  of  this  interest- 
ing manure,  for  theory  cannot  be  satisfied 
with  those  already  existing.  It  has  been 
usual  to  employ  a  less  quantity  by  weight 
of  nitrate  of  potash  than  of  nitrate  of  soda. 
This  procedure  seems  rather  empirical,  for 
unless  sanctioned  by  experience,  it  would 
d  priori  appear  to  be  better  to  add  the  great- 
est quantity  of  that  salt  which  possesses  the 
highest  equivalent.  Now  the  equivalent  of 
nitrate  of  potash  is  considerably  higher  than 
that  of  nitrate  of  soda. 

Charcoal  in  a  state  of  powder  must  be 
considered  as  a  very  powerful  means  of  pro- 
moting the  growth  of  plants  on  heavy  soils, 
and  particularly  on  such  as  consist  of  ar- 
gillaceous earth.* 

Ingenhouss  proposed  dilute  sulphuric  acid 
as  a  means  of  increasing  the  fertility  of  a 


do  not  exist  in  the  juice  in  an  isolated  state, 
but  generally  in  combination  with  certain 
alkaline  or  earthy  bases.  The  juice  of  the 
vine  contains  tartaric  acid,  that  of  the  sorrel 
oxalic  acid.  It  is  quite  obvious  that  a  pecu- 
liar action  must  be  in  operation  in  the  or- 
ganism of  the  vine  and  sorrel,  by  means  of 
which  the  generation  of  tartaric  and  oxalic 
acid  is  effected  ;  and  also  that  the  same  ac- 
tion must  exist  in  all  plants  of  the  same 
genus.  A  similar  cause  forces  corn-plants 
to  extract  silicic  acid  from  the  soil.  The 
number  of  acids  found  in  different  plants  is 
very  numerous,  but  the  most  common  are 
those  which  we  have  already  mentioned ;  to 
which  may  be  added  acetic,  malic,  citric, 
aconitic,  maleic,  kinovic  acids,  &c. 

When  we  observe  that  the  proper  acids 
of  each  family  of  plants  are  never  absent 
from  it,  we  must  admit  that  the  plants  be- 
longing to  that  family  could  not  attain  per- 
fection, if  the  generation  of  their  peculiar 
acids  were  prevented.  Hence,  if  the  pro- 
duction of  tartaric  acid  in  the  vine  were  ren- 


with  this  material.  100  parts  of  concen- 
trated sulphuric  acid  diluted  with  from  800 
to  1000  parts  of  water,  are  equivalent  to 
176  parts  of  gypsum. 


SUPPLEMENTARY  CHAPTER. 


ON   THE  CHEMICAL    CONSTITUENTS  OF    SOILS. 


soil.  Now,  when  this  acid  is  sprinkled  on  |  dered  impossible,  it  could  not  produce 
calcareous  soils,  gypsum  (sulphate  of  lime)  grapes,  or  in  other  words,  would  not  fructify, 
is  immediately  formed,  which  of  course  Now  the  generation  of  organic  acids  is  pre- 
prevents  the  necessity  of  manuring  the  soils  vented  in  the  vine,  and,  indeed,  in  all  plants 

which  yield  nourishment  to  men  and  ani- 
mals, when  alkalies  are  absent  from  the  soil 
in  which  they  grow.  The  organic  acids  in 
plants  are  very  rarely  found  in  a  free  state ; 
in  general,  they  are  in  combination  with 
potash,  soda,  lime,  or  magnesia.  Thus, 
silicic  acid  is  found  as  silicate  of  potash, 
acetic  acid  as  acetate  of  potash  or  soda, 
oxalic  acid  as  oxalate  of  potash,  soda,  or 
lime,  tartaric  acid  as  bitartrate  of  potash, 
&c.  The  potash,  sodT,  lime,  and  magnesia 
in  these  plants  are,  therefore,  as  indispensa- 


THE  fertility  of  a  soil  is  much  influenced 
by  its  physical  properties,  such  as  its  poro- 
sity, colour,  attraction  for  moisture,  or  state 
of  disintegration.  But  independently  of 
these  conditions,  the  fertility  depends  upon 
the  chemical  constituents  of  which  the  soil 
is  composed. 

We  have  already  shown,  at  considerable 
length,  that  those  alkalies,  earths,  and  phos- 
phates, which  constitute  the  ashes  of  plants, 
are  perfectly  indispensable  for  their  deve- 
lopement ;  and  that  plants  cannot  flourish 
upon  soils  from  which  these  compounds  are 
absent.  The  necessity  of  alkalies  for  the 
vital  processes  of  plants  will  be  obvious, 
when  we  consider  that  almost  all  the  differ- 


cellent  manure  for  his  land.  The  crops  obtained 
by  means  of  it  presented  the  same  general  charac- 
ters as  those  manured  with  nitrate  of  potash,  and 
exhibited  a  greater  intensity  of  colour.  If  this  is 
found  uniformly  to  be  the  case,  it  will  very  much 
strengthen  the  supposition  that  the  action  of  ni- 
trate of  soda  is  due  to  its  alkaline  constituent. — 
ED. 

*  For  much  valuable  information  on  the  sub- 
ject of  manures,  see  "  Agricultural  Chemistry," 
vol.  viii.  of  Sir  H.  Davy's  collected  Works. 


ble  for  their  existence  as  the  carbon  from 
which  their  organic  acids  are  produced. 

In  order  not  to  form  an  erroneous  conclu- 
sion regarding  the  processes  of  vegetable 
nutrition,  it  must  be  admitted  that  plants  re- 
quire certain  salts  for  the  sustenance  of  their 
vital  functions,  the  acids  of  which  salts  exist 
either  in  the  soil  (such  as  silicic  or  phos- 
phoric acids)  or  are  generated  from  nutri- 
ment derived  from  the  atmosphere.  Hence, 
if  these  salts  are  not  contained  in  the  soil,  or 
if  the  bases  necessary  for  their  production 
be  absent,  they  cannot  be  formed,  or  in  other 
words,  plants  cannot  grow  in  such  a  soil. 
The  juice,  fruit,  and  leaves  of  a  plant  can- 
not attain  maturity,  if  the  constituents  ne- 
cessary for  their  formation  are  wanting,  and 
salts  must  be  viewed  as  such.  These  salts 
do  not,  however,  occur  simultaneously  in 
all  plants.  Thus,  in  saline  plants,  soda  is 
the  only  alkali  found ;  in  corn  plants,  lime 
and  potash  form  constituents.  Several  con- 
tain both  soda  and  potash,  some  both  potash 
and  lime ;  whilst  others  contain  potash  and 

•  rw^i  •  i  •  "         M 


magnesia.     The 
manner.     Thus 


acids   vary 
plant 


one 


may 


s  imilar 
contain 


CONSTITUENTS   OF   SOILS. 


71 


phosphate  of  lime,  a  second,  phosphate  of 
magnesia,  a  third,  an  alkali  combined  with 
silicic  acid,  and  a  fourth,  an  alkali  in  com- 
bination with  a  vegetable  acid.  The  re- 
spective quantities  of  the  salts  required  by 
plants  are  very  unequal.  The  aptitude  of  a 
soil  to  produce  one,  but  not  another  kind  of 
plant,  is  due  to  the  presence  of  a  base  which 
the  former  requires,  and  the  absence  of  that, 
indispensable  for  the  developernent  of  the 
latter.  Upon  the 'correct  knowledge  of  the 
bases  and  salts  requisite  for  the  sustenance 
of  each  plant,  and  of  the  composition  of  the 
soil  upon  which  it  grows,  depends  the 
whole  system  of  a  rational  theory  of  agri- 
culture; and  that  knowledge  alone  can  ex- 
plain the  process  of  fallow,  or  furnish  us 
with  the  most  advantageous  methods  of  af- 
fording plants  their  proper  nourishment. 

Give — so  says  the  rational  theory — to  one 
plant  such  substances  as  are  necessary  for 
its  developement,  but  spare  those,  which  are 
not  requisite,  for  the  production  of  other 
plants  that  require  them. 

It  is  the  same  with  regard  to  these  bases 
as  it  is  with  the  water  which  is  necessary 
for   the    roots   of   various    plants.     Thus, 
whilst  one  plant  flourishes  luxuriantly  in  an 
arid  soil,  a  second  requires  much  moisture, 
a  third  finds  necessary  this  moisture  at  the 
cpmmencement  of  its  developement,  and  a 
fourth  (such  as  potatoes)  after  the  appear- 
ance of  the  blossom.     It  would  be  very  er- 
roneous to    present   the  same  quantity  of 
water  to  all  plants  indiscriminately.     Yet  j 
this  obvious  principle  is  lost  sight  of  in  the  | 
manuring  of  plants.     An  empirical  system  I 
of  agriculture  has  administered  the  "same  ' 
kind  of  manures  to  all  plants ;  or  when  a 
selection  has  been  made,  it  was  not  based 
upon  a  knowledge  of  their  peculiar  charac- 
ters or  composition. 

The  cost  of  labour  in  England  has  given 
rise  to  the  production  of  much  ingenuity  in 
the  invention  of  machines,  which  have  pro- 
duced improvements  in  the  mode  of  appli- 
cation of  manures.  In  order  to  use  these 
with  advantage,  pulverulent  manures  are 
employed,  instead  of  the  common  stable 
manure,  whioh  is  generally  mixed  with 
much  straw. 

The  necessity  for  such  forms  of  manure 
naturally  suggested  the  employment  of  bone 
dust,  dried  dung,  lime,  ashes,  &c.  Now,  ' 
although  by  tnese  mean*  the  necessary 
phosphates  are  mrmshed  to  a  soil,  and  solii 
animal  excrements  rendered  unnecessary, 
they  have  led  to  the  neglect  of  the  liquid 
excrements,  that  is,  ol  the  urine  of  men  and 
animals,  which  is  thus  completely  lost  to 
agriculture.  For  although  the  meadows 
receive,  during  autumn  and  winter,  when 
cattle  are  fed  upon  them,  the  solid  and  liquid 
excrements  of  these  animals,  yet  the  urine 
of  man,  into  which  all  the  nitrogenous  con-  t 
stituents  of  animals  are  finally  deposited,  is 
completely  lost  to  the  fields.  This  most  im- 
portant of  all  manures,  so  properly  estimated 
in  FlantJers,  Germany,  and  China,  is  alto- 


gether lost  to  the  English  agriculturist.  Ir» 
large  towns  it  is  either  allowed  to  run  into 
the  rivers,  or  sink  into  the  ground  in  such  a 
manner  as  to  be  of  no  benefit  to  the  vegeta- 
ble kingdom. 

The  most  important  growth  in  England 
is  that  of  wheat ;  then  of  barley,  oats,  beans, 
and  turnips.  Potatoes  are  only  cultivated 
to  a  great  extent  in  certain  localities ;  rye, 
beet-root,  and  rape-seed,  not  very  generall; . 
Lucerne  is  only  known  in  a  few  districts, 
whilst  red  clover  is  found  universally.  Now, 
the  selection  of  inorganic  manures  for  these 
plants  may  be  fixed  upon  by  an  examina- 
tion of  the  composition  of  their  ashes.  Thus 
wheat  must  be  cultivated  in  a  soil  rich  in 
silicate  of  potash.  If  this  soil  is  formed 
from  feldspar,  mica,  basalt,  clinkstone,  or 
indeed  of  any  minerals  which  disintegrate 
with  facility,  crops  of  wheat  and  barley  may 
be  grown  upon  it  for  many  centuries  in  suc- 
cession. But,  in  order  to  support  an  unin- 
terrupted succession,  the  annual  disintegra- 
tion must  be  sufficiently  great  to  render 
solutle  a  quantity  of  silicate  of  potash  suf- 
ficient for  the  supply  of  a  full  crop  of  wheat 
or  barley.  If  this  is  not  the  case,  the  soil 
must  either  be  allowed  to  lie  fallow  from 
time  to  time,  or  plants  may  be  cultivated 
upon  it  which  contain  little  silicate  of  pot- 
ash, or  the  roots  of  which  are  enabled  to 
penetrate  deeper  into  the  soil  than  corn 
plants  in  search  of  this  salt.  During  this 
interval  of  repose,  the  materials  of  the  soil 
disintegrate,  and  potash  in  a  soluble  state  is 
liberated  on  the  layers  exposed  to  the  action 
of  the  atmosphere.  When  this  has  taken 
place,  rich  crops  of  wheat  may  be  again 
expected. 

The  alkaline  phosphates,  as  well  as  the 
phosphates  of  magnesia  and  lime,  are  ne- 
cessary for  the  production  of  all  corn-plants. 
Now,  bones  contain  the  latter,  but  none  of 
the  former  salts.  These  must,  therefore,  be 
furnished  by  means  of  night-soil,  or  of 
urine,  a  manure  which  is  particularly  rich 
in  them.*  Wood  ashes  have  been  found 
very  useful  for  wheat  in  calcareous  soils  ; 
for  these  ashes  contain  both  phosphate  of 
lime  and  silicate  of  potash.  In  like  manner 
stable  manure  and  night-soil  render  clayey 
soils  fertile,  by  furnishing  the  magnesia  in 
which  they  are  deficient.  The  ashes  of  all 
kinds  of  herbs  and  decayed  straw  are  capable 
of  replacing  wood  ashes. 

A  compost  manure,  which  is  adapted  to 
furnish  all  the  inorganic  matters  to  wheat, 
oats,  and  barley,  may  be  made,  bv  mixing 
equal  parts  of  bone  dust  and  a  solution  of 
silicate  of  potash  (known  as  soluble  gluss  in 
commerce,)  allowing  this  mixture  to  dry  in 
the  air,  and  then  adding  10  or  12  parts  ol 
gypsum,  with  16  parts  of  common  salt. 
Such  a  compost  would  render  unnecessary 


*  It  has  been  already  stated  that  bran  contains 
phosphate  of  soda  and  phosphate  of  magnesia,  so 
that  it  is  useful  as  a  manure  where  phosphates  are 
desired. — ED. 


7-2 


AGRICULTURAL   CHEMISTRY. 


J.he  anh.ial  manures,,  which  act  by  their  in- 
organic ingredients.  According  to  Berthier, 
100  parts  of  the  ashes  of  wheat  straw  con- 
tain— 

Of  matter  soluble  in  water    -  -        9*0 

Of  matter  insoluble  in  water        •  81 '0 

Now  100  parts  of  the  soluble  matter  con- 
tain— 

Carbonic  acid  •  •  -a  trace 

Sulphuric  acid       ...  2'0 

Muriatic  acid  .  .  .       13-Q 

Silica          -  -  .  -  35-0 

Votash  and  Soda        ...      50.0 

100-0 

100  parts  of  the  insoluble  matter  contain — 
Carbonic  acid        -       •     -  •    ,  0 

Phosphoric  acid          »  •  •         1*2 

/C1*l* 


'Silica 
Lime  -  • , 

Oxide  of  Iron  and  Charcoal 
Potash 


75.0 
•        5-8 
10-0 
8-0 

100.0 

The  silicate  of  potash  employed  in  the 
preparation  of  the  compost  described  above 
must  not  deliquesce  on  exposure  to  the  air, 
but  must  give  a  gelatinous  consistence  to 
the  water  in  which  it  is  dissolved,  and  dry 
to  a  white  powder  by  exposure.  It  is  only 
attractive  of  moisture  when  an  excess  of 
potash  is  present,  which  is  apt  to  exert  an 
injurious  influence  upon  the  tender  roots  of 
plint^.  In  those  cases  where  silicate  of 
j)ut;ish  cannot  be  procured,  a  sufficiency  of 
wood  ashes  will  supply  its  place.* 

All  culinary  vegetables,  but  particularly 
the  cruciferae,  such  as  mustard,  (sinams 
alba  and  nigra,)  contain  sulphur  in  notable 
quantity.  The  same  is  the  case  with  turnips, 
the  different  varieties  of  •  rape,  cabbage, 
celery,  and  red  clover.  These  plants  thrive 
best  in  soils  containing  sulphates  ;  hence  if 
these  salts  do  not  form  natural  constituents 
of  the  soil,  they  must  be  introduced  as  ma- 
nure. Sulphate  of  ammonia  is  the  best 
salt  for  this  purpose.  It  is  most  easily  pro- 
cured by  the  addition  of  gypsum  or  sulphate 
of  ironf  (green  vitriol)  to  putrefied  urine. 


*  In  some  parts  of  the  grand-duchy  of  Hesse, 
where  wood  is  scarce  and  dear,  it  is  customary 
for  the  common  people  to  club  together  and  build 
baking  ovens,  which  are  heated  with  straw  instead 
of  wood.  The  ashes  of  this  straw  are  carefully 
collected  and  sold  every  year  at  very  high  prices. 
The  farmers  there  have  found  by  experience  that 
the  ashes  of  straw  form  the  very  best  manure  for 
wheat ;  although  it  exerts  no  influence  on  the 
growth  of  fallow-crops  (potatoes  or  the  legumi- 
nosae.  for  example.)  The  stem  of  wheat  grown 
in  this  way  possesses  an  uncommon  strength. 
The  cause  of  the  favourable  action  of  these  asnes 
will  be  apparent,  when  it  is  considered  that  all 
corn-plants  require  silicate  of  potash ;  and  that 
the  ashes  of  straw  consist  almost  entirely  of  this 
compound. — ED. 

t  If  sulphate  of  iron  be  emploved,  it  ought  not 
to  be  added  in  great  excess,  and  the  urine  must 
be  exposed  to  the  air  for  some  time  after,  for  the 
purpose  of  converting  the  iron  into  the  peroxide. 
A  salt  of  the  protoxide  of  iron  is  injurious  to 
vegetation. 


Horn,  wool,  and  hoofs  of  cattle,  contain 
sulphur  as  a  constituent,  so  that  they  will 
be  found  a  valuable  manure  when  adrninis 
tered  with  sqluble  phosphates,  (with  urine, 
for  example.) 

Phosphate  of  magnesia  and  ammonia 
forms  the  principal  inorganic  constituent  of 
the  potato ;  salts  of  potash  also  exist  in  it, 
but  in  very  limited  quantity.  Now  the  soil 
is  rendered  unfitted  for  its  cultivation,  even 
though  the  herb  be  returned  to  it  after  the 
removal  of  the  crop,  unless  some  means  are 
adopted  to  replace  the  phosphate  of  magnesia 
removed  in  the  bulbous  roots.  This  is  best 
effected  by  mixtures  of  night-soil  with  bran, 
magnesian  limestone,  or  the  ashes  of  certain 
kinds  of  coal.  I  applied  to  a  field  of  pota- 
toes manure,  consisting  of  night- soil  and 
sulphate  of  magnesia,  (Epsom  salts,)  and 
obtained  a  remarkably  large  crop.  The  ma- 
nure was  prepared  by  adding  a  quantity  ol 
sulphate  of  magnesia  to  a  mixture  of  urine 
and  faeces,  and  mixing  the  whole  with  the 
ashes  of  coal  or  vegetable  mould,  till  it  ac- 
I  quired  the  consistence  of  a  thick  paste, 
which  was  thus  dried  by  exposure  to  the 
sun. 

It  has  been  formerly  mentioned,  that  the 
secondary  and  tertiary  limestones  contain 
potash  :  marl,  and  the  calcareous  minerals 
used  for  the  preparation  of  hydraulic  mortar, 
may  be  particularly  specified.  These  have 
been  found  to  form  excellent  manures  for 
heavy  clayey  soils,  particularly  for  such  as 
disintegrate  with  difficulty.  They  are  most 
efficacious  when  burnt,  but  can  only  be  ap- 
plied in  this  state  after  harvest,  and  ought 
to  be  ploughed  into  the  soil  as  quickly  aj 
possible.  By  the  action  of  lime  upon  clay, 
the  potash  contained  in  the  latter  is  rendered 
soluble.  This  may  easily  be  shown  by  mix- 
ing one  part  of  marl  with  half  its  weight  of 
burned  lime,  adding  water,  and  setting  aside 
the  mixture  to  repose  for  some  time.  Even 
after  a  space  of  24  hours,  an  appreciable 
quantity  of  potash  may  be  detected  in  the 
water.* 

A  most  striking  proof  of  the  influence  of 
potash  upon  vegetation  has  been  furnished 
by  the  investigations  of  the  "  administration" 
of  tobacco  in  Paris.  For  many  years  accu- 
rate analyses  of  the  ashes  of  various  sorts 
of  tobacco  have  been  executed,  by  the  orders 
of  the  "  administration ;"  and  it  has  been 
found,  as  the  result  of  these,  that  the  value 
of  the  tobacco  stands  in  a  certain  relation  to 


*  One  of  the  causes  of  the  advantages  produced 
by  subsoil  ploughing  is,  that  it  exposes  the  soil  to 
the  disintegrating  influences  of  the  atmosphere. 
Hence  it  is  that  the  subsoil  plough  is  so  beneficial 
in  siliceous  soils,  and  exerts  no  apparent  effect 
upon  those  which  contain  much  clay.  The  former 
disintegrate  and  liberate  their  potash  both  with 
facility  and  rapidity  ;  whilst  the  disintegration  of 
the  latter  proceeds  with  slowness,  and  no  appre- 
ciable effects  are  produced.  (See  Journal  of  the 
Agricultural  Society,  vol.  ii.,  p.  27.)  It  is  proba- 
ble, however,  that  if  the  land  received  a  dressing 
of  lime  after  subsoil  ploughing,  the  eFects  would 
be  produced  more  rapidly. — ED. 


COMPOSITION   OF   SOILS. 


73 


ihe  quantity  of  potash  contained  in  the 
ashes.  By  this  means  a  mode  was  furnished 
of  distinguishing  the  different  soils  upon 
which  the  tobacco  under  examination  had 
been  cultivated,  as  well  as  the  peculiar  class 
to  which  it  belonged.  Another  striking  fact 
WAS  also  disclosed  through  these  analyses. 
Certain  celebrated  kinds  of  American  tobacco 
were  found  gradually  to  yield  a  smaller 
quantity  of  ashes,  and  their  value  dimi- 
nished in  the  same  proportion.  For  this  in- 
formation I  am  indebted  to  M.  Pelouze,  pro- 
fessor of  the  Polytechnic  School  in  Paris. 

There  are  certain  plants  which  contain 
either  no  potash,  or  mere  traces  of  it.  Such 
are  the  poppy,  (papaver  somniferwn,}  which 
generates  in  its  organism  a  vegetable  alka- 
loid, Indian  corn,  (zea  wui?/s,)and  helianthus 
tuberosu-s.  For  plants  such  as  these  the  pot- 
ash in  the  soil  is  of  no  use,  and  farmers  are 
well  aware  that  they  can  be  cultivated  with- 
out rotation  on  the  same  soil,  particularly 
when  the  herbs  and  straw,  or  their  ashes, 
are  returned  to  the  soil  after  the  reaping  of 
the  crop. 

One  cause  of  the  favourable  action  of  the 
nitrates  of  soda  and  potash  must  doubtless 
be,  that  through  their  agency  the  alkalies 
which  are  deficient  in  a  soil  are  furnished  to 
it.  Thus  it  has  been  found  that  in  soils  de- 
ficient in  potash,  the  nitrates  of  soda  or  pot- 
ash have  been  very  advantageous;  whilst 
those,  on  the  other  hand,  which  contain  a 
sufficiency  of  alkalies,  have  experienced  no 
beneficial  effects  through  their  means.  In 
the  application  of  manures  to  soils  we  should 
be  guided  by  the  general  composition  of  the 
ashes  of  plants,  whilst  the  manure  applied 
to  a  particular  plant  ought  to  be  selected 
with  reference  to  the  substances  which  it 
demands  for  its  nourishment.  In  general,  a 
manure  should  contain  a  large  quantity  of 
alkaline  salts,  a  considerable  proportion  of 
phosphate  of  magnesia,  and  a  smaller  pro- 
portion of  phosphate  of  lime ;  azotised  ma- 
nure and  ammoniacal  salts  cannot  be  too 
frequently  employed. 

In  the  following  part  of  this  chapter  I 
shall  describe  a  number  of  analyses  of  soils 
executed  by  Sprengel,  together  with  obser- 
vations on  their  sterility  and  fertility,  as 
stated  by  that  distinguished  agriculturist. 
It  is  unnecessary  to  describe  the  modus  ope- 
randi  used  in  the  analyses  of  these  soils,  for 
this  kind  of  research  will  never  be  made  by 
farmers,  who  must  apply  to  the  professional 
chemist,  if  they  wish  for  information  regard- 
ing the  composition  of  their  soils. 

Under  the  term  surface-soil,  we  mean  that 
portion  of  soil  which  is  on  the  surface ; 
whilst  by  subsoil  we  mean  that  which  is  be- 
low the  former,  and  out  of  the  reach  of  the 
ordinary  plough. 

CHEMICAL    COMPOSITION   OF    CERTAIN   SOILS, 
ACCORDING    TO    ANALYSIS. 

1.  Surface-soil  (A)  a  good  loamy  soil, 

*rom  the  vicinity  of  Gandersheim.     It  is  re- 

10 


markable  for  producing  uncommonly  fine 

red  clover   when   manured  with   gypsum. 

(B)  is  an  analysis  of  the  subsoil.     100  parts 

contain : — 

(A)          (B) 

Silica,  with  fine  siliceous  sand    -91*331      93883 

Alumina 1*344        1*944 

Peroxide  of  iron,  with  a  little  pro- 
toxide   1-562  2-226 

Peroxide  of  manganese  -  -    0'082        0.320 

Magnesia  and  silica,  in  combina- 
tion with  sulphuric  acid  and 
humus  -  -  -  -  0-800  0'720 

Magnesia,  with  silica  and  humic 
acid  combined  -  -  0'440  0'340 

Potash,  in  combination  with  silica    0*156        0'105 

Soda,  principally  in  combination 
with  silica,  and  a  little  as  com- 
mon salt  -  -  -  -  0'066  0'060 

Phosphoric  acid  -  -  -    0'098        0190 

Sulphuric  acid  in  combination 
with  lime  ....  0-111  0'012 

Chlorine  (in  common  salt)          -    0  012        0*012 

Humus,  with  traces  of  azotised 
matter 4'100  0*184 

100-000    100000 

An  inspection  of  the  above  analyses  will 
show  that  the  soil  contains  a  very  small  pro- 
portion of  salts  of  sulphuric  acid — a  circum- 
stance which  accounts  for  the  favourable 
action  of  gypsum  upon  it. 

2.  The  surface-soil  (A)  is  a  fine-grained 
loamy  soil  from  Gandersheim,  distinguished 
for  the  remarkably  large  crops  of  beans, 
peas,  tares,  &c.,  which  it  produces  when 
manured  with  gypsum.  (B)  is  the  analysis 
of  the  subsoil.  100  parts  contain  : — 

(A)  (B) 

Silica,  with  fine  siliceous  sand    -  90*221  92*324 

Alumina  -  -  -     2*106  2'262 

Peroxide  and  protoxide  of  iron  -    3*951  2*914 

Peroxide  of  manganese  -  -     0*960  2*960 

Lime,  principally  combined  with 

phosphoric  acid  and  humus     -     0*539  0*532 


Magnesia,  with  silicate   of  pot- 
ash. &c.          • 
Potash 

Soda       - 

Phosphoric  acid        •  - 

Sulphuric  acid  (in  gypsum) 
Chlorine  (in  common  salt) 
Humus  and  azotised  matter 
Loss        - 


0*730  0-340 

0-067  0-304 
O'OIO     a  trace 

0-367  0-122 

a  trace  0*010 

0*100  0*004 

0.900         

0-140  0-228 


100*000     100-000 

The  analysis  of  this  soil  shows,  that,  with 
the  exception  of  gypsum,  every  ingredient 
is  present  which  is  requisite  for  the  nourish- 
ment of  leguminous  plants.  Hence  it  is 
that  gypsum  exerts  such  a  favourable  influ- 
ence upon  it. 

3.  Surface-soil  (A)  a  strong  loamy  sand, 
from  Brunswick.  (B)  the  analysis  of  the 
subsoil.  100  parts  contain  : — 

CA)         (B) 

Silica,  with  coarse  siliceous  sand  95'698      96*880 
Alumina  -  -  -     0'504        0*890 

Peroxide  and  protoxide  of  iron  -    2*496        1*496 
Peroxide  of  manganese  •  -  a  trace     a  trace 

Lime  -  -  -      -    0*038        0.019 

Magnesia  -  -  -    0*147        0*260 

Potash  and  soda,   the  greatest 

part  in  combination  with  silica  0*090  0*079 
Phosphate  of  iron  -  0*164  0*110 


74 


AGRICULTURAL   CHEMISTRY. 


Sulphuric  acid  (in  gypsum/ 
Chlorine  (in  common  salt) 
Humus 


vA)        (B) 

•  0-007  a  trace 

•  O'OIO  a  trace 

•  0-846         0-226 

100-000  100-000 


This  soil  was  much  improved  by  manur- 
ing with  lime  and  ashes.  It  was  then  found 
well  fitted  for  clover,  beans,  and  peas. 

4.  Surface-soil  (A)  a  loamy  sand,  from 
the  environs  of  Brunswick.  (B)  analysis 
of  the  subsoil  at  the  depth  of  3  feet.  100 
parts  contain: — 


(A) 

(B) 

Silica  and  fine  siliceous  sand 

94-724 

97-340 

Alumina             - 

1-638 

0.806 

Protoxide  and  peroxide  of  iron 

with  manganese          *V 

1-960 

1-201 

Lime                        -       •<--«-• 

1-028 

0-296 

Magnesia            ... 

a  trace 

0-095 

Potash  and  soda 

0-077 

0-112 

Phosphoric  acid           v  *  's 

0-024 

0-015 

Gypsum      ... 
Chlorine  of  the  salt        • 

o-oio 

0207 

a  trace 
a  trace 

Humus        ... 

0-512 

0-135 

100-000   100-000 

This  soil  produces  luxuriant  crops  of  lu- 
cerne and  sainfoin,  as  well  as  of  all  other 
plants  the  roots  of  which  penetrate  deeply 
into  the  ground.  The  reason  is  apparent. 
The  subsoil  contains  magnesia,  which  is 
wanting  in  the  surface-soil. 

5.  Surface-soil  (A)  a  loamy  sand,  from 
the  environs  of  Brunswick.  (B)  analysis 
of  the  subsoil  at  a  depth  of  2  feet.  100  parts 
contain : — 

(A) 

Silica,  with  coarse  siliceous  sand   95'843 
Alumina  ".;  -        -  ••;   0'600 

Protoxide  and  peroxide  of  iron       T800 
Peroxide  of  manganese    -  a  trace 

Lime,  in  combination  with  silica    0'038 
Magnesia  m    do.  do.      0'006 

Potash  and  soda  ;  •:*          -    O'OOS 

Phosphate  of  iron     -  *          0'198 

Sulphuric  acid     ...    0'002 
Chlorine        -  -  .          0'006 

Humus  soluble  in  alkalies          -     I'OOO 
Humus  insoluble  hi  alkalies  0*502 


(B) 

95.190 
1-600 
2-200 

a  trace 
0.455 
0-160 
0-004 
0-400 

a  trace 

o-ooi 


100-000   100-000 

This  soil  is  characterised  by  its  great 
sterility.  White  clover  could  not  be  made 
to  grow  upon  it.  The  obvious  cause  of  its 
poverty  is  a  deficiency  of  lime,  magnesia, 
potash,  and  gypsum;  for  we  find  that  the 
fertility  of  the  soil  was  much  increased  by 
manuring  it  with  marl.  The  white  clover, 
which  formerly  had  refused  to  grow  on  this 
soil,  now  grew  upon  it  with  much  luxuri- 
ance. The  aridity  of  the  soil  could  not  have 
been  the  cause  of  its  sterility,  for  the  stiff 
nature  of  the  subsoil  on  which  it  rested  pre- 
vented a  deficiency  of  moisture. 

6.  Surface-soil  (A)  a  loamy  land  from  the 
environs  of  Brunswick.  (B)  the  analysis 
of  the  subsoil,  at  a  depth  of  2  feet.  100 
parts  contain : — 


Silica,  with  fine  siliceous  sand  - 
Alumina 

Protoxide  and  peroxide  of  iron 
Peroxide  of  manganese 
Lime,  in  combination  with  silica 
Magnesia,  idem 

Potash,  idem  • 

Soda,  idem 
Phosphate  of  iron 
Gypsum      ... 
Common  salt      - 
Humus  soluble  in  alkalies  - 
Humus  accompanied  by  azotised 
matter  .  .  . 

Resinous  matter 


(A)  B) 

94-998  96.490 

0-610  T083 

1-080  1.472 

0.268  0-400 

0-141  0.182 

0-208  0-205 

0-050  0-070 

0-044  0-050 

0086  0-030 

0-041  0-005 

0-004  0-003 

0-400  0-010 

2.070        .   .   . 
a  trace      .   .   . 

100.000    100.000 

This  soil  is  by  no  means  remarkable  for 
its  sterility,  but  is  decidedly  improved  by 
manuring  with  burned  ferruginous  loam. 
It  is,  however,  rendered  still  better  by  the 
use  of  burned  marl — a  manure  which  is 
rich  in  iron,  potash, gypsum,  and  phosphate 
of  lime.  The  marl  does  not  exert  so  favour- 
able an  action  when  applied  in  its  natural 
state;  but  the  heat  liberates  the  potash  from 
the  insoluble  compound  which  it  forms  with 
silica. 

7.  Surface-soil  (A)  a  loamy  sand,  from 
Brunswick.  (B)  analysis  of  the  subsoil  at 
a  depth  of  1£  feet.  100  parts  contain : — 


Silica,  with  fine  siliceous  sand 

Alumina  - 

Protoxide  and  peroxide  of  iron 

Peroxide  of  manganese 

Lime,  combined  with  silica 

Magnesia,  idem       •  <*  \. 

Potash,  idem      •  *  .     ,"   * 

Soda,  idem  -        ^  »/  '     ..•  -• 

Phosphate  of  iron 

Sulphuric  acid  contained  in  gyp- 
sum ... 

Chlorine  - 

Humus  soluble  in  alkalies  - 

Humus,  with  azctised  organic 
remains  • 


(A)  (B) 

92-980  96-414 

0-820  1-000 

1-666  1-370 

0.188  0-240 

0-748  0-364 

0-168  0-160 

0-065  0-045 

0-130  0082 

0-246  0-043 

a  trace        O'OOS 
a  trace        0'007 
0-764        0270 

2-225        '    '    • 
100-000     100-000 

The  soil  when  manured  with  gypsum  is 
very  favourable  to  the  production  of  legu- 
minous plants  and  red  clover.  But  it  is 
very  remarkable,  on  account  of  the  rust 
which  always  attacks  the  corn  plants  which 
may  be  grown  upon  it.  This  rust  and  mil- 
dew (uredo  linearis,  puccinia  grawiims)  is  a 
disease  which  attacks  the  stem  and  leaves, 
and  is  quite  different  from  the  brand  (iiredo 
glumarum)  which  appears  on  the  seeds  and 
organs  of  reproduction.  Rust  is  most  fre- 
quently detected  on  plants  growing  on  soils 
which  contain  bog-ore  or  turf-iron  ore.  Ac- 
cording to  Sprengel,  rust  contains  phosphate 
of  iron,  to  which  this  chemist  ascribes  the 
origin  of  the  disease.  It  is  very  possible  that 
other  causes  may  operate  in  the  production 
of  similar  diseases. 

8.  Soil,  a  fine-grained  loamy  marl,  from 
the  vicinity  of  Schoningen.  It  produces 
corn,  which  is,  however,  very  liable  to 
blight.  100  parts  contain : — 


COMPOSITION    OF    SOILS. 


Silica,  with  siliceous  sand 

Alumina         -  - 

Protoxide  and  peroxide  of  iron    • 

Peroxide  of  manganese 

Lime  (principally  carbonate) 

Magnesia,  idem  ... 

Potash,  with  silica 

Soda  with  silica        -  - 

Phosphate  of  iron       ... 

Sulphuric  acid  with  Hme 

Carbonic  acid,  with  lime  and  magnesia 

Humus  soluble  in  alkalies 

Humus     -  « 


100-000 

It  will  be  observed  that  a  considerable 
quantity  of  phosphate  of  iron  is  contained 
in  this  soil,  and  the  corn  which  grows  upon 
it  is,  as  in  the  former  case,  disposed  to  rust. 

9.  Surface-soil  (A)  a  loamy  soil,  from 
Brunswick,  remarkable  on  account  of  pro- 
ducing buck-wheat,  which  is  exceedingly 
poor  in  the  grain.  (B)  analysis  of  the  sub- 
soil at  a  depth  of  1^  foot.  100  parts  con- 
tain : — 


(A) 

Silica,  with  coarse  siliceous  sand  95*114 
Alumina  -  -  -  1*080 
Protoxide  and  peroxide  of  iron  1*900 
Protoxide  and  peroxide  of  man- 
ganese -  -  -  0*320 
Lime,  in  combination  with  silica  0*380 
Magnesia,  idem  ;'  >  >  -  0*300 
Potash,  with  silica  •  0  020 
Soda  -  -  -  .  •  0.004 
Phosphate  of  iron  -  ';  V  ,  0*052 
Suiphuric  acid  with  lime  •  0*006 
Chlorine  (in  common  salt)  0  005 
Humus  soluble  in  alkalies  «  0*619 
Humus  -  -  0*200 


(B) 

92*458 
2*530 
2-502 

0*920 

0-710 

0*551 

0.120 

0*034 

0*175 

a  trace 

a  trace 


100-000    100-000 

By  manuring  the  land  with  wood  ashes, 
the  soil  is  enabled  to  produce  buck-wheat, 
with  rich  grain  ;  the  leguminous  plants  also 
thrive  luxuriantly  upon  it.  This  increased 
fertility  is  due  to  the  ashes,  by  means  of 
which  both  potash  and  phosphates  are  sup- 
plied to  the  land. 

10.  Subsoil  of  a  loamy,  sandy  soil,  from 
Brunswick.  It  is  remarkable  for  having 
produced  excellent  crops  of  hops  for  a  long 
series  of  years.  100  parts,  by  weight,  con- 
sist of: — 


Silica,  with  siliceous  sand 

-    95.660 

Protoxide  and  peroxide  of  iron 
Peroxide  of  manganese 
Lime,  in  combination  with  silica 

-     1.616 
0.240 
.    0.083 

Sulphuric  acid                                  • 
Chlorine                     . 
Humus  soluble  in  alkalies    - 

0.003 
•    a  trace 
0.080 
-     0.360 

100.000 

Aitnough  the  hops  contain  a  large  quan- 
tity of  potash,  soda,  phosphoric  acid,  sul- 
phuric acid,  lime,  and  magnesia,  yet  we  do 
not  find  that  these  exist  in  the  soil  in  super- 
abu  ndant  quantity.  IN  or  is  it  necessary  that 


they  should,  for  the  roots  of  the  hops  pene 
trate  8  or  10  feet  deep  into  the  soil,  and  search 
out  the  materials  fitted  to  nourish  the  plants. 
Hence  it  is  that  hops  thrive  well  on  soils 
comparatively  poor  in  their  proper  ingredi- 
ents. The  same  is  the  case  with  all  plants 
of  a  similar  nature,  the  roots  of  which  pos- 
sess a  tendency  to  extend  in  search  of  food ; 
we  see  this  particularly  in  lucerne  and  sa*n- 
foin. 

SOILS    OF   HEATHS. 

1 1 .  Soil  of  a  heath  converted  into  arable 
land,  in  the  vicinity  of  Brunswick.     It  is 
naturally   sterile,  but  produces  good  crops 
when  manured  with  lime,  marl,  cow-dung, 
or  the  ashes   of  the  heaths  which  grow 
upon  it. 

Silica,  and  coarse  siliceous  sand  -  -  71.504 
Alumina  -  -  -  -  0.780 

Protoxide  and  peroxide  of  iron,  principally 

combined  with  humus  -  0.420 

Peroxide  of  manganese,  idem  -  -  0.220 
Lime,  idem  -  -  ...  0.134 

Magnesia,  idem  ....  0.032 

Potash  and  soda,  principally  as  silicates  -  0.058 
Phosphoric  acid,  (principally  as  phosphate 

of  iron)  .....  0.115 
Sulphuric  acid  (in  gypsum)  •  -  -0.018 
Chlorine  (in  common  salt)  ...  0.014 
Humus  soluble  in  alkalies  -  .  .  9.820 
Humus,  with  vegetable  remains  •  14.975 
Resinous  matters 1.910 

100.000 

Ashes  of  the  soil  of  the  heath,  before  be 
ing  converted  into  arable  land  : — 
Silica,  with  siliceous  sand       ...    92.641 
Alumina  -        -  -        -        1.352 

Oxides  of  iron  and  manganese  -  -  2.324 
Lime,  in  combination  with  sulphuric  and 

phosphoric  acids  ....  0.929 
Magnesia,  combined  with  sulphuric  acid  -  0.283 
Potash  and  soda  (principally  as  sulphates 

and  phosphates  ....  0.564 
Phosphoric  acid,  combined  with  lime  -  0.250 
Sulphuric  acid,  with  potash,  soda  and  lime  1.620 
Chlorine  in  common  salt  -  -  0.037 

100.000 

12.  Surface-soil  of  a  fine-grained  loam, 
from  the  vicinity  of  Brunswick.     It  is  re- 
markable from  the  circumstance,  that  not  a 
single  year  passes  in  which  corn  plants  are 
cultivated  upon  it  without  the  stem  of  the 
plants  being  attacked  by  rust.     Even  the 
grain  is  covered  with  a  yellow  rust,  and  is 
much  shrunk.     100  parts  of  the  soil  con- 
tain : — 

Silica  and  fine  siliceous  sand        -        -        87.8f>9 

Alumina          - 2.652 

Peroxide  of  iron  with  a  large  proportion  of 

protoxide                     -         -         -         •  5.132 

Protoxide  and  peroxide  of  manganese      -  0.840 

Lime  principally  combined  with  silica  -  1.459 

Magnesia,  idem        •         -         -         -         -  0.280 

Potash  and  soda,  idem             ...  0.090 

Phosphoric  acid  in  combination  with  iron  0.505 

Sulphuric  acid  in  combination  with  lime  0.068 

Chlorine  in  common  salt          -        .        -  0.006 

Humus 1.109 


100.000 


70 


AGRICULTURAL   CHEMISTRY. 


This  soil  does  not  suffer  from  want  of  1  it,  in  such  a  manner  that  they  were  not  ex 
drainage  :  it  is  well  exposed  to  the  sun,  is  I  hibited  by  analysis. 

in  an  elevated  situation,  and  in  a  good  state  Oats  and  barley  were  sown  on  this  land 
of  cultivation.  In  order  to  ascertain  whether  I  the  second  year  after  being  reclaimed,  and 
the  rust  was  due  to  the  constituents  of  the  both  suffered  much  from  rust,  although  dif- 


soil,  (phosphate  of  iron  ?)  or  to  certain  for- 
tuitous circumstances  unconnected  with 
their  operation,  a  portion  of  the  land  was 
removed  to  another  locality,  and  made  into 
an  artificial  soil  of  fifteen  inches  in  depth. 
Upon  this  barley  and  wheat  were  sown ;  but 
it  was  found,  as  in  the  former  case,  that  the 
plants  were  attacked  by  rust,  whilst  barley 
growing  on  the  land  surrounding  this  soil 
was  not  at  all  affected  by  the  disease.  From 
this  experiment  it  follows,  that  certain  con- 
stituents in  the  soil  favour  the  developement 
of  rust. 

13.  Soil  of  a  heath,  which  had  been 
brought  into  cultivation  in  the  vicinity  of 
Brunswick.  The  analysis  was  made  before 
any  kind  of  crops  had  been  grown  upon  it. 
Corn-plants  were  first  reared  upon  the  new 
soil,  but  were  found  to  be  attacked  by  the 
rust,  even  on  those  parts  which  had  been 
manured  respectively  with  lime,  marl,  pot- 
ash, wood  ashes,  bone-dust,  ashes  of  the 
heath  plant,  common  salt  and  ammonia. 
100  parts  contain  : — 

Silica  with  coarse  siliceous  sand          • 
Alumina          -        -        -        •        - 
Protoxide  and  peroxide  of  iron  in  combina- 
tion with  phosphoric  and  humic  acids 
Protoxide  and  peroxide  of  manganese 
Lime  in  combination  W'fh  humus          •    - 
Magnesia  idem          -  -         •   ,,     * 

Potash  and  soda  ... 

Phosphoric  acid       •        -        -        • 
Sulphuric  acid  •  •     .    - 

Chlorine          ------ 

Humus  soluble  in  alkalies     - 
Rssinous  matters  - 

Coal  of  humus  and  water 


51-337 
0-528 

0-398 
.  0-003 

0-230 
.  0-040 

o-oio 

•  0-066 
0'022 

•  0-014 
13-210 

2-040 
32-100 

100-000 


The  next  analysis  represents  the  soil  after 
being  burnt.  100  parts  by  weight  of  the  soil 
left  after  ignition  only  50  parts.  100  parts 
of  these  ashes  consisted  of: — 

Silica  and  siliceous  sand 
Alumina  : 

Peroxide  of  iron      ----- 

Peroxide  of  manganese 
Lime  in  combination  with  sulphuric  acid 
Magnesia  combined  with  silica 
Potash  and  soda  - 

Phosphoric  acid  (principally  as  phosphate  of 
iron  ------ 

Sulphuric  acid      • 

Chlorine          •  • 

100-000 

By  comparing  this  analysis  with  the  one 
which  has  preceded  it,  an  increase  in  cer- 
tain of  the  constituents  is  observed,  particu- 
larly with  respect  to  the  sulphuric  acid,  pot- 
ash, soda,  magnesia,  oxide  of  iron,  oxide  of 
manganese,  and  alumina.  From  this  it  fol- 
lows, that  the  humus,  or  in  other  words,  the 
vegetable  remains,  must  have  contained  a 
quantity  of  these  substances  confined  within 


ferent  pans  of  the  soil  were  manured  with 
marl,  lime  and  peat-ashes;  whilst  other  por- 
tions were  left  without  manure.  In  the  first 
year,  all  the  different  parts  of  the  field  pro- 
duced potatoes,  but  they  succeeded  best  in 
those  divisions  which  hid  been  manured 
with  peat-ashes,  lime  and  marl.  In  the 
second  year,  oats  mixed  with  a  little  barley 
were  sown  upon  the  soil ;  and  the  straw 
was  found  to  be  strongest  on  the  parts  treated 
with  peat-ashes,  lime,  marl,  and  ashes  of 
wood.  Red  clover  was  sown  on  the  third 
year;  it  appeared  in  best  condition  on  those 
portions  of  the  soil  manured  with  marl  and 
lime.  Upon  the  divisions  of  the  field  which 
had  been  left  without  manure,  as  well  as  on 
those  manured  with  bone-dust,  potash,  am- 
monia and  common  salt,  the  clover  scarcely 
appeared  above  ground.  The  divisions  ot 
the  field,  which  had  been  manured  in  the 
first  year  with  peat-ashes,  ammonia,  and 
ashes  of  wood,  were  sown  with  buckwheat 
after  the  removal  of  the  first  crop  of  clover. 
The  buckwheat  succeeded  very  well  on  all 
the  divisions,  yet  a  marked  difference  was 
perceptible  in  favour  of  the  portion  treated 
with  ammonia.  These  experiments  show 
us,  that  a  dressing  of  lime  did  not  completely 
remove  from  the  soil  its  tendency  to  impart 
rust  to  the  plants  grown  upon  it.  Never- 
theless it  is  highly  probable,  that  as  soon  as 
the  protoxide  of  iron  became  converted  into 
the  peroxide  by  exposure  to  the  atmosphere, 
lime  would  possess  more  power  in  decom- 
posing the  phosphate  of  iron. 

14.  Subsoil  of  a  loamy  soil  in  the  vicinity 
of  Brunswick.  It  is  remarkable  from  the 
circumstance  that  sainfoin  cannot  be  culti- 
vated upon  it  more  than  two  or  three  years 
in  succession.  The  portion  analysed  was 
taken  from  a  depth  of  five  feet.  100  parts 
contained: — 

Silica  with  very  fine  siliceous  sand  -  90'035 
Alumina  -  -  -  -  -  1'976 

Peroxide  of  iron  -----        4'700 

Protoxide  of  iron T115 

Protoxide  and  peroxide  of  manganese  -        0-240 

Lime '  0'0'?2 

Magnesia O'llS 

Potash  and  soda      -        -         -    _     -        -     0'300 
Phosphoric  acid,  combined  with  iron    -        0'098 
Sulphuric  acid  (the  greatest  part  in  combina- 
tion with  protoxide  of  iron)  1  '399 
Chlorine           •                 ...          a  trace 

100000 

Now  the  results  of  the  analysis  give  a  suffi- 
cient account  of  the  failure  of  the  sainfoin. 
The  soil  contains  above  one  per  cent,  of 
sulphate  of  protoxide  of  iron  (green  vitriol 
of  commerce,)  a  salt  which  exerts  a  poison- 
ous action  upon  plants.  Lime  is  not  pre- 
sent in  quantity  sufficient  to  decompose  this 
salt.  Hence  it  is  that  sainfoin  will  not  thrive 
on  this  soil,  nor  indeed  lucerne,  or  any  other 


CONSTITUENTS  OF  SOILS. 


77 


of  the  plants  with  deep  roots.  The  evil  can 
not  be  obviated  by  any  methods  sufficiently 
economical  for  the  farmer,  because  the  soi 
cannot  be  mixed  with  lime  at  a  depth  of  five 
or  six  feet.  For  many  years  experiment? 
have  been  made  in  vain,  in  order  to 
this  soil  for  sainfoin  and  lucerne,  and  much 
expense  incurred,  which  could  all  have  been 
saved,  had  the  soil  been  previously  analysed 
This  example  affords  a  most  convincing 
proof  of  the  importance  of  chemical  know- 
ledge to  an  agriculturist. 

15.  Surface  soil  (A)  of  a  sandy  loam  in 
the  vicinity  of  Brunswick,  celebrated  for  its 
beautiful  crops  of  clover,  rye,  potatoes,  anc 
barley.  The  clover  must,  however,  always 
be  manured  with  gypsum.  (B)  is  an  ana- 
lysis of  the  subsoil  at  the  depth  of  1^  foot 
100  parts  contain: — 

(A)  (B) 

Silica  with  coarse  siliceous  sand  94 '274  95'146 

Alumina        -        -        -         -  1.560  1*416 
Peroxide  of  iron  with  a  little 

phosphoric  acid  -         -        -  2'496  2*528 

Peroxide  of  manganese       -  0*240  0'320 

Lime CHOO  0*297 

Magnesia  -  :  -  0'230  0'221 
Potash  and  soda  ...  0*102  0*060 
Sulphuric  acid  -  "•  '  .'  0'039  0'012 
Chlorine  ....  Q'005  a  trace 
Humus  soluble  in  alkaline  car- 
bonates -  ...  0'444 
Humus  ;  *  .  -  -  •  0'210 

100-000    100-000 

The  best  property  of  this  soil  is,  that  its 
inferior  layers  are  nearly  of  the  same  com- 
position as  the  superior,  as  far  as  the  inor- 
ganic constituents  are  concerned.  It  is  a 
soil  upon  which  the  plants  mentioned  above 
will  seldom  fail ;  and  as  it  possesses  a  very 
good  mixture  to  the  depth  of  four  or  five 
feet,  it  would,  doubtless,  produce  lucerne 
also. 

16.  Surface-soil  (A)  of  a  sandy  loam  in 
the  vicinity  of  Brunswick.  It  produces  ex- 
cellent crops  of  oats  and  clover,  when  the 
latter  is  manured  with  gypsum.  (B)  Ana- 
lysis of  the  subsoil  taken  from  a  depth  of  1^ 
foot.  100  parts  contain: — 

Silica  and  siliceous  sand         -  94 '4 30 

Alumina    ....  1-474 
Peroxide  of  iron  with  a  little 

phosphoric  acid        -        -  2*370 

Peroxide  of  manganese  -  a  trace 

Lime,  principally  combined  with 

silica       ....  0*680 

Magnesia,  idem     -        •        -  0*290 

Potash       ....  0-190? 

Soda     -        -        ...  0*0105 

Sulphuric  acid    -      •  -        .  a  trace 

Chlorine        ....  0-015 

Humus       •        «        -        .  0*541 


(B) 

89*660 
0*980 

7-616 
a  trace 

0*954 
0*520 

0*150 

a  trace 

a  trace 

0*120 


100-000      100000 

Both  the  surface  and  the  sub-soil  contain 
only  traces  of  sulphuric  acid.  Hence  the 
ipplication  of  gypsum  is  attended  with  great 
benefit.  Without  doubt,  marl  and  lime  would 
be  found  of  essential  service. 
17.  Soil  from  the  environs  of  Brunswick,  I 


consisting  principally  of  sand,  and  eminently 
remarked  for  its  sterility.  It  was,  however, 
much  improved  by  manuring  it  with  marl 
which  contained  24  per  cent,  of  lime,  to- 
gether with  magnesia,  manganese,  potash, 
soda,  gypsum,  and  common  salt.  100  parts 
of  the  soil  contained : — 

Silica  and  siliceous  sand 
Alumina     -        .... 
Protoxide  and  peroxide  of  iron 
Peroxide  of  manganese 
Lime  in  combination  with  silica 
Magnesia,  idem          ... 

Potash 

Soda  -  - 

Phosphoric  acid  combined  with  iron 
Sulphuric  acid    .... 
Chlorine        -  ... 

Humus      ..... 


95-841 
0-600 
1-800 

a  trace 
0-038 
0-006 
0-002 
0003 
0*198 
0-002 
0-006 
1*504 


100*000 

Here  another  proof  is  presented,  that  a 
soil  may  be  very  rich  in  humus  and  yet  be 
very  poor  as  regards  fertility.  By  means  of 
the  marl,  the  inorganic  ingredients  of  the 
plants  are  furnished  to  the  soil,  which  con 
tains  them  in  very  small  quantity. 

18.  The  soil  of  a  very  fertile  loam  from 
the  vicinity  of  Walkenried.  100  parts  con- 
tain : — 


Silica,  with  coarse-grained  silicious  sand 
Alumina 


88-456 
0-650 
Peroxide  and  protoxide  of  iron,  accompanied 

by  much  magnetic  iron  sand  -  -  5*608 
Peroxide  of  manganese  ...  0'560 

Carbonate  of  lime 1-063 

Carbonate  of  magnesia  ...  1-68? 
Potash  combined  with  silica  ...  0'04*> 
Soda  combined  with  silica  -  -  0-012 

Phosphate  of  lime  ....  0'035 
Sulphate  of  lime  a  trare 

Common  salt 0-.<05 

Humus  soluble  in  alkalies  ...  0  55C 
Humus  with  several  azotised  organic  re- 

mains  .....      1-333 

100-000 

Gypsum  acts  most  excellently  upon  this 
land.  The  soils  in  the  southern  range  of 
the  Harz  mountains  are  particularly  re- 
marked for  containing  more  magnesia  than 
lime.  Even  the  different  varieties  of  marl 
contain  a  considerable  quantity  of  magnesia. 
Thus,  in  a  specimen  of  marl  obtained  from 
the  vicinity  of  Walkenried,  I  obtained  55$ 
per  cent,  carbonate  of  lime,  and  30£  pei 
cent,  carbonate  of  magnesia ;  in  another  41 
per  cent,  lime,  and  1 1  per  cent,  magnesia  ; 
and  in  a  third,  47  £  per  cent,  lime,  and  13} 
per  cent,  magnesia.  Most  of  these  soils 
contain  also  £ — 1  per  cent,  of  gypsum, 
and  £ — 1  per  cent,  phosphate  of  lime,  and 
are,  therefore,  well  fitted  for  manuring  other 
ands. 

19.  Subsoil  of  a  loam  from  a  depth  of  1$ 
bot.  It  occurs  in  the  vicinity  of  Brunswick. 
The  surface-soil  is  remarkable  on  account 
)f  producing  beautiful  red  clover  on  being 
manured  with  gypsum;  although  the  so^l 
tself  contains  only  traces  of  lime,  magnesia, 
>otash,  and  phosphoric  acid.  100  parts  of 
the  subsoil  contained  : — 


78 


AGRICULTURAL   CHEMISTRY. 


Silica  and  coarse  siliceous  sand        •  88*980 

Alumina  -            -            -            .            •  2*240 

Protoxide  and  peroxide  of  iron        •  3*840 

Peroxide  of  manganese  -            «            -  a  trace 

Carbonate  of  lime     ...  2*720 

Carbonate  of  magnesia   ...  0'600 

Potash  and  soda        -            -            -  0'095 

Phosphate  of  lime           ...  1.510 

Sulphate  of  lime       ...  a  trace 

Common  salt       ....  0*015 

100-000 

At  a  greater  depth  than  the  subsoil  of 
which  the  analysis  is  here  given,  the  soil 
passes  into  mar],  which  contains  20|  per 
cent,  of  carbonate  of  lime.  The  sulphuric 
acid  deficient  in  the  soil  was  supplied  by 
means  of  the  gypsum. 

SOILS  IN  THE  KINGDOM  OF  HANOVER. 

20.  (A)  Analysis  of  a  barren  heath-soil 
from  Aurich  in  Ostfriesland ;  (B)  a  sandy 
soil  containing  much  humus  but  also  sterile ; 
(C)  a  sandy  soil  possessing  the  same  cha- 
racters as  B.     100  parts  contained : — 

(A)         (B)        (C) 
Silica  and  coarse  siliceous 

sand       -  -  95-778  85'973  96*721 

Alumina         -  -        0'320      0320  0*370 

Protoxide  and  peroxide  of 

iron         -  -  0*400      0-440      0*480 

Peroxide  of  manganese  a  trace  a  trace  a  trace 
Lime  -  -  0*286  0.160  O'OOS 
Magnesia  -  •  0'060  0:240  0*080 
Soda  -  .:>  0*036  0*012  0*036 

Potash  •  -a  trace  a  trace  a  trace 

Phosphoric  acid     •  a  trace  a  trace  a  trace 

Sulphuric  acid  -      a  trace  a  trace  a  trace 

Chlorine  in  common  salt  0*052  0'019  0*058 
Humus  -  -  0-768  0*636  O'SOO 

Vegetable  remains  2*300      8*200      1'450 

100-000  100*000  100-000 

21.  Analysis  of  the  clayey  subsoil  of  a 
moor,  which,  after  being  burned,  is  used  as 
a  manure  to  the  above  soils,  A,  B,  C.     100 
parts  contain : — 

Silica  and  siliceous  sand       -  •  v       87'219 

Alumina  ....        4*200 

Peroxide  of  iron  with  a  little  phosphoric  acid  5*200 
Peroxide  of  manganese  •  '•  0*310 

Lime  •  •  .;    *"  '          0*320 

Magnesia  -  -  .  -       0*380 

Potash  principally  combined  with  silica  0*130 
Soda  principally  combined  with  silica  -  0*274 
Sulphurii?  acid  combined  with  lime,  magne- 
sia, and  potash  ...  0*965 
Chlorine  ....  0'002 
Humus  -  •  -  -  -  I'OOO 

100*000 

By  comparing  this  analysis  with  that  of 
the  three  soils  which  have  preceded,  it  will 
be  observed  that  this  subsoil  is  fitted  to  im- 
part to  them  those  mineral  ingredients  in 
which  they  are  deficient. 

22.  Surface  soil  of  a  barren  heath  in  the 
vicinity  of  Walsrode  in   Luneberg.      100 
parts  by  weight  contain  : — 

Silica  and  siliceous  sand  ...  92*216 

Alumina        -            ...  0*266 

Peroxide  of  iron  «...  0  942 

Protoxide  of  iron      ...  0*394 


Peroxide  of  manganese  <•  -  -    a  trace 

Lime,  in  combination  with  silica,  sulphuric 

acid,  and  humus  -  -  -       1*653 

Magnesia,  in  combination  with  silica  0'036 

Potash,  principally  in  combination  with  silica  0'038 
Soda  -  ... 

Phosphoric  acid  .... 
Sulphuric  acid          ... 
Chlorine  ..... 
Humus,  soluble  in  alkaline  carbonates 
Humus    ..... 
Resinous  matter       ... 

100-000 

This  soil  contains  a  large  quantity  of 
protoxide  of  iron,  which,  together  with  a 
deficiency  of  phosphoric  acid,  is  the  cause 
of  its  sterility.  But  when  this  land  was 
manured  with  the  ashes  of  peat,  it  was 
rendered  much  more  fertile.  The  ashes 
used  for  this  purpose  were  found  to  contain 
in  100  parts : — 

Silica,  with  siliceous  sand  •;**  -  96*352 
Alumina  -  -  -  1*859 
Peroxide  and  protoxide  of  iron,  with  a  lit- 
tle phosphoric  acid  -  -  1*120 
Peroxide  of  manganese  •  •  .  0  160 
Lime  -  -  •  .  0*112 
Magnesia  -  -  •  0*141 
Potash  -  •*** '  -  -i,  .  0-093 
Soda  .....  0.007 
Sulphuric  acid  ...  0-152 
Chlorine  -  ,  .,'  -  -  -  0'004 

100-000 

The  ashes,  on  exposure  to  the  air,  ab- 
sorbed ammonia. 

23.  Analysis  of  a  very  fertile  loamy  soil 
from  Gottingen.  It  is  very  rich  in  humus, 
and  produces  beautiful  crops  of  peas,  beans, 
lucerne,  and  beet.  The  sieve  separates  from 
100  parts  of  the  soil : — 

Small  stones,  principally  limestone          -  1 

Quarzy  sand,  with  a  little  magnetic  iron  sand     15 
Earthy  part         '<.•;,-   ..  » •-.'--   •  • ._:      84 

100 

100  parts  of  the  soil,  freed  from  stones, 
consists  of : — 

Silica,  and  fine  siliceous  sand      .  -    83*298 

Alumina,  combined  with  silica          -  T413 

Alumina,  partly  in  combination  with  humus  3'715 
Peroxide  and  protoxide  of  iron,  in  combi- 
nation with  silica          -  -  -      0.724 
Peroxide  and  protoxide  of  iron,  partly  free 

and  partly  in  combination  with  humus  2*244 
Peroxide  and  protoxide  of  manganese  0.280 

Lime,  with  coal  of  humus,  sulphur,  and 

phosphoric  acid  -  .    •      T814 

Magnesia,  combined  with  silica         •  0'422 

Magnesia,  combined  with  humus  •      0'400 

Potash  »-..'•        -  -  -  *         0-003 

Soda        -  ...  .      0*001 

Phosphoric  acid          •  •  •  0'166 

Sulphuric  acid     ....      0*069 
Chlorine          ....  0003 

Carbonic  acid  (as  carbonate  of  lime)      •      0*440 
Humus,  soluble  in  alkalies         •  0*789 

Humus,  with  a  little  water    •  -  3*250 

Nitrogenous  matter         ...       0*960 
Resinous  matter        ...          a  trace 

100-000 
The  subsoil  is  of  tne  same  composition  as 


CONSTITUENTS   OF   SOILS. 


79 


the  surface,  with  this  difference  only,  that  it 
contains  more  potash,  soda,  and  chlorine,* 
and  is  interspersed  with  fragments  of  fresh- 
water shells.  Hence  it  is  that  the  soil  pro- 
duces the  deep-rooted  plants  in  such  luxu- 
riance. 

24.  Soil  of  a  sterile  moor,  which  had 
been  burned  three  times,  and  upon  which 
buckwheat  had  been  cultivated.  100  parts 
contained : — 

Humus,  soluble  in  alkalies         •  -       9'250 

Vegetable    remains,    charcoal,    quarzy 
sand,  and  earthy  particles  •  90*750 

100-000 

100  parts  by  weight  left,  after  ignition,  10 
parts  of  ashes.  100  parts  of  these  ashes 
consisted  of: — 

Silica  and  siliceous  sand 

Alumina        -  •       .     • 

Peroxide  of  iron 

Peroxide  of  manganese        •  .• 

Carbonate  of  lime        ''.  •  *' .  * 

Carbonate  of  magnesia 

Potash     -  -  .          -.    : 

Soda  -  -  '  ., 

Phosphoric  acid 

Sulphate  of  lime  (gypsunO  •  • 

Chlorine 


•  79-600 
•  •          6-288 

•  0-857 
0-400 

•  7-652 
1-640 
0-080 
0-028 

•  0215 
3-235 

•  0-005 

100-000 

Soils  such  as  this,  after  having  been 
burned  several  times,  and  made  to  produce 
buckwheat,  are  completely  deprived  of 
their  potash  and  soda;  and  in  consequence 
of  this  are  rendered  quite  barren.  Hence  it 
is  that  ashes  of  wood  exert  such  an  astonish- 
ing effect  upon  them. 

25.  Analysis  of  a  very  fertile  loamy  sand, 
from  Osnabriick,  near  Rotherfeld.  It  is  re- 
markable for  being  manured  only  once  every 
10  or  12  years,  and  bears  beautiful  wheat  as 
the  last  crop.  100  parts  contain: — 

Silica,  with  coarse  siliceous  sand 
Alumina        .... 
Peroxide  and  protoxide  of  iron,  with  a 

little  phosphoric  acid   ... 
Peroxide  of  manganese 
Carbonic  acid,  and  a  little  phosphate  of 

lime      -  .... 

Carbonate  of  magnesia 
Potash  and  soda 
Phosphoric  acid         •  * .  ' 

Sulphuric  acid     «... 
Chlorine        • 

Humus,  soluble  in  alkaline  carbonates  - 
Humus          .... 
Nitrogenous  matter        ... 


86-200 
2000 

2-900 

o-ioo 

4-160 
0-520 
0-035 
0-020 
0-021 
O'OIO 
0-544 
3-370 
0-120 

lOO'OOO 

The  soil  in  question  lies  on  the  southern 
exposure  of  a  hill,  which  consists  of  layers 
of  limestone  and  marl.  The  rain-water 
penetrates  through  these  layers,  and  becomes 
saturated  with  the  soluble  salts  contained  in 
them,  such  as  potash,  gypsum,  common 

*  The  portion  of  the  suface-soil  subjected  to 
analysis  was  taken  from  the  field  after  long-con- 
tinued rain.  Hence  the  small  quantity  of  salts  of 
Votaah  and  soda. 


salt,  lime,  magnesia,  and  saltpetre.  It  after- 
wards reaches  the  soil,  and  manures  it  with 
these  ingredients.  It  is  only  in  this  manner 
that  we  are  enabled  to  explain  the  fertility 
of  this  soil;  for,  reasoning  from  its  chemical 
composition,  we  would  be  induced,  a /mori, 
to  suppose  that  it  would  be  barren.  At  the 
base  of  this  hill,  certain  portions  of  the  land 
are  covered  with  calcareous  tuff,  containing 
the  above  salts:  a  fact  which  proves  that 
the  water  which  penetrates  through  the  soil 
must  also  contain  them  in  solution.  The 
large  proportion  of  humus  exhibited  by  the 
analysis  depends  upon  the  nature  of  the 
manure  to  which  it  was  treated. 

26.   Analysis  of  a   heavy   alluvial  soil, 
from  Norden.     100  parts  contain : — 


Silica,  and  very  fine  siliceous  sand    .     • 
Alumina        -        •'*•'• 
Peroxide  of  iron  ... 

Peroxide  of  manganese 
Lime       ..... 
Magnesia      -  -  -  *\ 

Potash        -  -  -  •      \« 

Soda,  in  combination  with  silica 
Phosphoric   acid,   in  combination  with 
lime     -  .  .  *  - 

Sulphuric  acid  -  -  '<•'.  - 

Chlorine  - 

Hurnus,  soluble  in  alkalies   - 
Humus  and  nitrogenous  matter 


84-543 
3-458 
3-488 
0-560 
0-319 
0*740 

a  trace 
6-004 

0-260 
0-008 
0-008 
0-416 
0-196 

100-000 

The  portion  of  the  soil  subjected  to  analy- 
sis was  taken  at  a  depth  of  10  inches,  from 
a  field  which  had  received  no  manure  for 
several  years.  It  had  previously  produced 
in  succession  barley,  beans,  wheat,  and 
grass,  the  latter  for  two  years.  The  soil  is 
remarkable,  in  a  chemical  point  of  view, 
from  the  laige  quantity  of  soda  which  it 
contains.  Although  the  sulphuric  acid, 
chlorine,  and  potash  are  present  in  small 
quantity,  yet  this  does  not  present  any  bar- 
rier to  the  developement  of  the  plants,  as  the 
surface-soil  is  18  inches  in  depth. 

27.  Analysis  of  a  heavy  alluvial  soil  in 
the  vicinity  of  Norden.  100  parts  contain  :  — 

Silica,  and  very  fine  siliceous  sand 
Alumina       -        -    •-          - 
Peroxide  of  iron  <  . 

Peroxide  of  manganese        • 
Carbonate  of  lime  •  • 

Carbonate  of  magnesia          - 
Potash,  in  combination  with  silica 
Soda,  idem    -  .. 

Phosphoric  acid  .. 

Sulphuric  acid  .. 

Chlorine  -  -  - 

Humus,  soluble  in  alkalies      - 
Humus  with  nitrogenous  matter 


79  '174 
3'016 
4-960 
0'600 
2'171 
2-226 
0'025 
6  '349 
0'534 

a  trace 
0005 
0'782 
0'158 

100-000 

The  specimen  for  analysis  was  taken  at  a 
depth  of  10  inches  from  the  surface  of  a 
field,  which  had  been  manured  five  years 
previously,  and  had  produced  since  that  time 
rape,  rye,  wheat,  and  beans.  The  crops  of 
all  these  were  plentiful,  and  of  excellent 
quality.  It  is  singular  that  this  soil,  which 
i  contains  such  a  small  proportion  of  gypsum, 


AGRICULTURAL   CHEMISTRY. 


should  be  adapted  for  the  cultivation  of 
beans,  and  must  be  ascribed  to  the  depth  of 
the  surface-soil.  Yet,  notwithstanding  this, 
gypsum  would  form  a  beneficial  manure  to 
the  land. 

28.  Analysis  of  a  very  fertile  alluvial  soil, 
from  Honigpolderj  no  manure  had  ever 
been  applied  to  it.  100  parts  contain : — 

Siliceous  sand  separated  by  the  sieve 
Earthy  portion  of  the  soil    « 


4-5 
95-5 

100.0 


100  parts  of  the  latter  consisted  of: — 

Silica,  and  fine  siliceous  sand  -•     64*800 

Alumina        -  •  •        **>'•,•  5*700 

Peroxide  of  iron  •  •  ^,  6'100 

Peroxide  of  manganese        -  -  0'090 

Lime       .....  5'880 

Magnesia       ....  0'840 
Potash,  principally  in  combination  with 

silica          -  -       :    •    -    '  '•>.'  0*210 

Soda,  idem  •  •  -  -  0'393 

Phosphoric  acid  combined  with  lime  0'430 

Sulphuric  acid,  idem  -  •  0'210 

Chlorine  (in  common  salt)  -  -  0'207 

Carbonic  acid,  combined  with  lime  3'92il 

Humus  soluble  in  alkalies        •         •  2'54'J 

Humus       ...        -  .  5-60-3 

Nitrogenous  matter          ...  i  5b2 

Water  -        -        ...  1*504 


100-000 

Corn  has  been  cultivated  for  seventy  years 
upon  this  soil,  which  has  never  received 
dung  or  any  other  kind  of  manure ;  it  is, 
however,  occasionally  fallowed.  The  sub- 
soil retains  the  same  composition  as  the 
surface-soil  for  a  depth  of  6—12  feet,  so  that 
it  may  be  considered  inexhaustible.  When 
one  portion  of  the  soil  is  rendered  unfitted 
for  use,  the  inferior  layers  are  brought  up  to 
the  surface. 

29.  Analysis  of  a  soil  from  Rahdingen, 
near  Balje.  In  this  case  the  sea  has  assisted 
in  the  formation  of  the  soil.  The  field 
yielded  beautiful  corn  after  being  manured 
with  stable  dung,  being  particularly  re- 
marked for  its  fine  crops  of  wheat,  beans, 
and  winter  barley.  100  parts  contain  : — 

Silica,  siliceous  sand,  and  silicates 
Alumina          -        .        •     "  . 
Peroxide  of  iron  •        • '       * 

Peroxide  of  manganese 

Lime 

Magnesia 

Potash  and  soda  soluble  in  water 
Phosphoric  acid  .... 

Sulphuric  acid          .... 
Chlorine  (in  common  salt)  •    '"  • 

Humus,  soluble  in  alkaline  carbonates 

Humus 

Nitrogenous  matter         ... 
Water        ..... 


-  87-012 

-  4-941 

-  2-430 

-  0-192 

-  0-292 

-  0-145 

-  0-005 

-  0-114 

-  0074 

-  0.003 

-  0-658 

-  2-668 

-  1-412 
0-042 


Peroxide  of  manganese 

Lime 

Magnesia 

Potash 

Soda 


-  -  2-OdO 
.  0-942 

-  -  1-740 
-  0-050 
.  0-012 


30.  Soil  of  a  field  remarkable  ft  :  produ- 
cing large  crops  of  hemp  and  hor&e-radish. 
100  parts  consisted  of: — 

Silica  and  siliceous  sand  -  84.021 

Alumina  ......     4-498 

Peroxide  of  iron 5-120 


Phosphoric  acid       .....  0'4S2 

Sulphuric  acid     ......  0'012 

Chlorine O'OOS 

Humus  soluble  in  alkaline  carbonates      -  0  897 

Humus  and  nitrogenous  matter  -    -  0'13$ 

100-000 

31.  Surface-soil  of  a  field  near  Dracken- 
burg ;  it  produces  very  bad  red  clover.     100 
parts  contain: — 

Silica,  with  very  fine  siliceous  sand  -  92*014 

Alumina  - 2 -652 

Peroxide  of  iron       -        -        «        -        -     3'192 
Peroxide  of  manganese        -        -        -    -    0'480 

Lime  0'243 

Magnesia  0'700 

Potash  combined  with  silica  •        -    0.125 

Soda,  idem          -         -         -         -         .     -     0-026 
Phosphoric  acid,  in  combination  with  lime    0'078 

Sulphuric  acid a  trace 

Chlorine  ......  a  trace 

Humus  and  nitrogenous  matter        •        -    0'150 
Humus  soluble  in  alkaline  carbonates      -    0'340 

100.000 

The  cause  that  clover  will  not  flourish  on 
this  soil  is  probably  due  to  the  deficiency  of 
gypsum  and  common  salt. 

32.  Surface-soil  of  a  field  near  Padding- 
buttel.     This   field   is  particularly  adapted 
for  the  growth  of  red  clover.     100  parts  con- 
sist of: — 

Silica  and  siliceous  sand 
Alumina          \"«  '_  -  » 
Peroxide  of  iron       • 
Peroxide  of  manganese 
Lime 
Magnesia 


93-720 
1-740 
2-060 
0-320 
0-121 
0-700 


Potash,  principally  in  combination  with  silica  0'062 

Soda,  idem  /*  "  "  - 

Phosphoric  acid        ^'»    -~  • 

Sulphuric  acid          .... 

Chlorine  (in  common  salt) 

Humus  soluble  in  alkaline  carbonates 

Humus  with  nitrogenous  matter 


0'109 

-  0-103 

-  0-005 

-  0-050 

-  0-890 

-  0-120 

100-000 


SOILS    IN    BOHEMIA. 


33.  Surface-soil  of  a  very  fertile  field  in 
the  province  of  Dobrawitz  and  Lautschin. 
100  parts  gave 

Siliceous  sand,  with  much  magnetic  iron 

sand  4'286 

Earthy  part  separated  by  the  sieve        •     -95714 

100-000 

An  aqueous  infusion  of  the  soil  contained 
gypsum,  common  salt,  magnesia,  and  hu- 
mus. 100  parts  of  the  soil  gave  : — 

Silica               89-175 

Alumina              ......  2-653 

Protoxide  and  peroxide  of  iron          -        •  3'136 

Peroxide  of  manganese        -        -        -     -  0'320 

Lime 1-200 

Magnesia             T040 

Potash,  in  combination  with  silica             •  0'075 

Soda,  idem  (principally)                 -         -     -  0'354 

Phosphoric  acid,  in  combination  with  lime  0  377 


CONSTIKJENTS    OF    SOILS. 


81 


Sulphuric  acid,  idem 
Chlorine  (in  common  salt) 
Humus  soluble  in  alkalies 
Humus        ... 
Nitrogenous  matter 


0-081  |  of  Nebstein.  It  has  never  been  manured  or 
0%066    allowed  to  lie  fallow,  and  yet  has  produced 
for  the   last  160   years  the  most  beautiful 


0-920 
0-456 


-    0-208 

100-000 

34  Surface-soil  of  a  very  fertile  field  in 
the  province  of  Dobrawitz  and  Laiitscliin. 
100  parts  of  the  earth  consisted  01': — 

Siliceous  sand,  with  a  little  magnetic  iron 

sand 43-780 

Finer  part  separated  by  the  sieve  •    56-220 


100-000 

100  parts  yielded  to  water  0-175  part  of 
salts,  consisting  of  common  salt,  gypsum, 
magnesia,  and  humic  acid.  100  parts,  by 
weight,  of  the  earth  consisted  of: — 

Silica       -        n       -        ••      -  ,.V-  89-634 

Alumina     -         -         -  -        -     -     3'224 

Protoxide  and  peroxide  of  iron 
Peroxide  of  manganese      «        • 
Lime  .... 

Magnesia  .... 

Potash  in  combination  with  silica 
Soda,  idem  .... 

Phosphoric  acid,  in  combination  with  lim 

Sulphuric  acid,  idem 

Chlorine  (in  common  salt) 

Humus  soluble  in  alkalies 

Humus  -         .   -  '' 

Nitrogenous  matter         ....    0*448 

100-000 

35.  Analysis  of  a  soil  formed  by  the  dis- 
integration of  basalt.     100  parts  of  the  earth 
consisted  of: — 

Siliceous  sand,  with  very  much  magnetic 

iron  sand  8*428 

Earthy  portion  of  the  soil        -'.'•'  J  i'V     91  "572 

100-000 

The  aqueous  infusion  of  the  earth  con- 
tained only  traces  of  common  salt  and  gyp- 
sum, with  humus,  lime,  and  magnesia. 
100  parts  consisted  of: — 

Silica        -      ..    "••  -  '    A      >       •         83-642 

Alumina 3'978 

Protoxide  and  peroxide  of  iron        -        -      5312 
Peroxide  of  manganese       -        -        -          0'960 
Lime     -        -        -        -        -        -  ^    -      1-976 

Magnesia      --:--•        0*650 
Potash,  in  combination  with  silica  •        •     0-080 
Soda,  idem      -        •        •        •        -        -     0' 145 
Phosphoric  acid,  in  combination  with  lime    0*273 
Sulphuric  acid,  idem  -  a  trace 

Humus  soluble  in  alkaline  carbonates        -    1*270 
Chlorine        -        -        -        -  •    a  trace 

Humus  -  -  -  •  .  -  -  0'234 
Nitrogenous  matter  ....  1*480 

100-000 

Manure  consisting  of  gypsum,  common 
salt,  or  ashes  of  wood,  would  be  highly  con- 
ducive to  the  fertility  of  this  land. 

SOILS  IN  THE  "  MARKGRAFSCHAFT  MAHREN." 

36.  Surface-soil  of  a  field  very  remarka- 


crops  •  thus  furnishing  a  remarkable  exam- 
ple of  unimpaired  fertility.  100*000  parts 
of  this  soil  consisted  of: — 

Course  and  fine  siliceous  sand,  with  a 

little  magnetic  iron  sand        -        -  35'400 

Earthy  matter        .....    64-600 

100-000 

100  parts  of  the  earth  yielded  to  water  0-010 
sulphuric  acid,  0*010  chlorine,  0*007  soda, 
0*012  magnesia,  0-010  potash,  with  a  little 
silica,  humus,  and  nitrogenous  matter,  but 
no  appreciable  trace  of  nitrates.  100  parts 
of  the  soil  contained  : — 

Silica -,    '  -  77-209 

Alumina    -    >     •     ' .'**'   «  8*514 

Peroxide  of  iron     -----  6*592 

Peroxide  of  manganese     '  *,->.    *,  1  "520 

Lime 0"927 

Magnesia  -..--.  1*160 
Potash,  principally  in  combination  with 

silica 0-140 

Soda,  idem               0'640 

Phosphoric  acid,  combined  with  lime  and 


Sulphuric  acid,  combined  with  lime       -  O'Ol  1 

Chlorine  (in  common  salt)     ...  O'OIO 

Humus  soluble  in  alkalies         -        -        -  0'978 

Humus 0540 

Nitrogenous  matter      .    ••       ...  T108 

100-000 

It  is  apparent  from  the  above  analysis 
that,  notwithstanding  the  long  period  during 
which  this  land  has  been  cultivated  without 
manure,  it  still  remains  very  rich  in  matters 
adapted  for  the  nutrition  of  plants. 

SOILS  IN  HUNGARY. 

37.  Analysis  of  a  very  fertile  soil  from 
Esakang.  100  parts  of  the  earth  con- 
tained : — 


Very  *»re  siliceous  sand 
matter    -       .    • 


2-820 

V  -••»•         97-180 

100-000 

The  aqueous  dpcoction  of  the  soil  contained 
principally  gypsum,  common  salt,  silica, 
magnesia,  and  humus.  100  parts  of  tlie  soil 
yielded : — 

Silica      -        -        •       >',.„.-        -  •   76-038 

Alumina    ------  4 '654 

Peroxide  and  protoxide  of  iron        -  -       6'112 

Peroxide  of  manganese        - 

Carbonate  of  lime  -        -    —  •        •  •      3'771 


Carbonate  of  magnesia     t- 
Potash  combined  with  silica 
Soda  combined  with  silica 
Phosphoric  acid,  combined  with  lime 
Sulphuric  acid    -        -        -        - 
Chlorine  in  common  salt 
Humus  soluble  in  alkalies 
Humus        - 
Nitrogenous  organic  matter    - 


4-066 
0-030 
1-373 
0546 
0-021 
0015 
1-160 
1-100 
0-208 

100-000 


ble    for   its   fertility.     The   field    is    called    Subsoil  of  the  same  field  at  a  depth  o "  two 
Haargraben,  and  is  situated  near  the  village  '  f-~*      1AA - — ;~*  ~f  • 


II 


feet.     100  parts  consist  of: — 


82 


AGRICULTURAL   CHEMISTRY. 


Very  fine  s,fuceou£  sand  with  scales  of 

mica  .... 

Earth  separated  by  the  sieve 


100  parts  of  the  earth  contain : — 

Silica  «  -  ... 

Alumina        -        -        -        - 

Peroxide  and  protoxide  of  iron    • 

Peroxide  of  manganese 

Carbonate  of  lime  •  "• 

Carbonate  of  magnesia  • 

Potash  combined  with  silica 

Soda,  principally  combined  with  silica    - 

Phosphoric  acid  combined  with  lime  • 

Sulphuric  acid,  idem 

Chlorine  in  common  salt        '"•  • 

Humus  soluble  in  alkalies 

Humus  with  nitrogenous  organic  matter 


59-581 
.     3-224 
4-896 
0-720 
17-953 
11-075 
0-150 
0-891 
0-846 
-  0-004 
0-004 
0-536 
0-120 

100-000 
BELGIUM. 

38.  Surface-soil  of  a  field  distinguished 
for  its  fertility.  It  had  received  no  manure 
for  twelve  years  previous  to  the  time  at 
which  the  analysis  was  executed.  The  ro- 
tation of  crops  for  the  latter  nine  years  was 
as  follows  : — 1.  beans,  2.  barley,  3.  potatoes, 
4.  winter  barley  with  red  clover,  5.  clover, 
6.  winter  barlev,  7.  wheat,  8.  oats ;  during 
the  ninth  year  it  was  allowed  to  lie  fallow. 
The  soil  is  more  clayey  than  loamy,  and  of 
a  very  fine  grain.  Water  extracted  from 
the  soil,  0-013  soda,  0-002  lime,  0-012  mag- 
nesia, 0-009  sulphuric  acid,  0-003  potash, 
0-003  chlorine,  with  traces  of  silica  and  hu- 
mus. 100  parts  contained : — 

Silica            -            -            -    '  64-517 

Alumina           -            -            ...»  4'810 

Peroxide  and  protoxide  of  iron      •            •  8*316 

Peroxide  of  manganese          •  "-  0'800 

Carbonate  of  lime         .   *  '         -            -  9'403 

Carbonate  of  magnesia            -            -  10'361 

Potash,  principally  combined  with  silica  O'lOO 

Soda                        ....  0-013 

Phosphoric  acid           •            -           *'.^  1-221 

Sulphuric  acid        -            • '          -  0'009 

Chlorine        -           ;•<>'         •            -  0"003 

Humus      -                        ...  0-447 


i  ric  acid,  potash,  soda,  and  manganese.     All 

2-408  I  Of  these  must  have  been  present  in  the  soil 

.   97-592  |  for  we  are  informed  that  it  produced  good 

mn.nnn  '  hops,  for  which  these  ingredients  are  indis- 

1UU  UUU  *•        j  -i 

pensable. 

40.  A  good  turnip  soil  from  Holkham, 


Norfolk,  yielded  to  Davy  : — 

!  Siliceous  sand 

Silica  ... 

Alumina 
Peroxide  of  iron, 
Carbonate  of  lime 
Vegetable  and  saline  matter     • 
Moisture 


100-000 


ENGLAND. 


39.  Surface-soil  of  a  ve«y  fertile  sandy 
field  from  the  vicinity  of  Tunbridge,  Kent, 
according  to  Davy.  100  parts  consisted 
of: — 


Loose  stones  and  gravel 

Sand  and  silica    • 

Alumina          ... 

Peroxide  of  iron  -  • 

Carbonate  of  lime         •  • 

Carbonate  of  magnesia 

Common  salt  and  extractive  matter 


Gypsum 
Mai 


latter  destructible  by  heat 
Vegetable  fibre 
Water        - 
Loss       .... 


13-250 
58-250 
3-250 
1-250 
4.750 
0.750 
0-750 
0-500 
3750 
3-500 
5-000 
5-000 


1-666 
1-222 
0-334 
7-000 
0-556 
0-334 


lOO'OOO 

In  this  case  also,  phosphoric  acid,  man- 
ganese,  potash,  magnesia,  &c.,   have   es- 
aped  detection  by  this  acute  chemist ;  yet 
doubtless  they  must  be  present  in  the  sorl, 
or  we  are  informed  that  it  produces  good 


turnips. 
41.  An 


excellent  wheat  soil   from    the 


neighbourhood  of  West  Drayton,  Middle- 
Davy.     100   parts   con- 


sex,  according  to 
tained : — 

Sand  and  silica 
Alumina       ^     - 
Carbonate  of  lime 
Humus  and  moisture 


-  72-800 
11-600 

-  11-200 

4.400 


100-000 

The  great  Davy,  who  was  convinced  of 
te  importance  of  the  inorganic  constituents 
f  soils,  has  omitted  to  detect  the  phospho- 


100-000 

This  analysis  has  been  executed  so  imper- 
fectly, that  it  only  conveys  a  very  feeble 
representation  of  the  nature  of  the  soil.  A 
soil  which  bears  good  wheat  must  contain 
phosphate  of  potash,  soda,  chlorine,  and 
sulphuric  acid  •  yet  none  of  these  are  exhi- 
bited by  the  analysis. 

42.  Suiface-soil  of  a  fertile  field  in  the 
neighbourhood  of  Bristol.     100  parts  con 
tained  : — 

Silica  and  siliceous  sand    ' 

Alumina  •  **"  .       •  *, 

Peroxide  of  iron     -       ^  • 

Lime  (carbonate)          ... 

Magnesia 

Humus  .... 

Saline  and  extractive  matter 

Water  -  -  - 

100-000 

Davy  has  made  several  analyses  of  vari- 
ous fertile  soils,  and  since  his  time  numerous 
other  analyses  have  been  published;  but 
they  are  all  so  superficial,  and  in  most  cases 
so  inaccurate,  that  we  possess  no  means  of 
ascertaining  the  composition  or  nature  of 
English  arable  land. 

SWEDEN. 

43.  Surface-soil  of  a  field  wbich  produces 
the  most  abundant  crops,  and  has   never 
been  manured.    (Berzelius.)    100  parts  con- 
sist of: — 

Siliceous  sand        ....  57"90G 

Silica H-500 

Alumina 2'00(> 

Phosphates  of  lime  »nd  iron    •  -          6'00<? 

Carbonate  of  lime  -  •  -  11.10* 

Carbonate  of  magnesia 
Insoluble  extractive  matter  •  •     1*250 


CONSTITUENTS   OF   SOILS. 


83 


inso'iuble  extractive  matter  destructible  by 

heat  -  -          4-000 

Animal  matter  •  •  -     1*600 

Resin    -  ...          0'250 

Loss          .....    0-400 


Humus,  soluble  in  alkalies 
Nitrogenous  organic  matter 
Wax  and  resinous  matter 


1-950 
0-236 
0-025 


100-000 

This  great  chemist  has  strangely  omitted 
to  detect  in  the  soil  potash,  soda,  chlorine, 
sulphuric  acid,  and  manganese.  As  this 
soil  is  eminent  for  its  fertility,  there  cannot 
be  the  slightest  doubt  that  all  these  ingre- 
dients must  have  existed  in  it  in  notable 
quantity. 

ISLAND    OF   JAVA. 

44.  A  very  fine-grained  loamy  soil,  co- 
loured yellow  by  peroxide  of  iron,  consisted 
of: — 

Silica  and  siliceous  sand  >'"-' 

Alumina  -  -  *"" 

Peroxide  and  protoxide  of  iron 
Peroxide  of  manganese 
Lime        •  ,• 
Magnesia          • 

Potash,  principally  in  combination 
silica  .  -  -  *,/j 

Soda,  idem        ... 
Phosphoric  acid     •  '•*.--. 

Sulphuric  acid 

Chlorine  •  V  " 

Humus  ... 

Water  with  carbonic  acid 


with 


67-660 

13-572 

10-560 

1-640 

0-912 

0-570 

0-030 
0184 
0-391 
0.038 
0010 
0-368 
4-065 


100-000 

WEST    INDIES    (PORTO    RICO.) 

45.  Surface-soil   of  a  very  barren  field. 
100  parts  contained  : — 

Silica  and  siliceous  sand  -  70"900 
Alumina  ....  6'996 
Peroxide  and  protoxide  of  iron  (much  mag- 
netic iron  sand)  :  v  .  .  6*102 
Peroxide  of  manganese  ••"*"  -  0'200 
Lime  -  -  -  .-*.:,  .  2'218 
Magnesia  -  .  ;&\:  -»"-  *  3'280 
Potash  -  •;•,•.  r  •  .  0-130 
Carbonate  of  soda  -  -  .'••>.  6'556 
Phosphoric  acid,  combined  with  lime  -  1-362 
Sulphuric  acid,  combined  with  lime  •  0"149 
Chlorine  in  common  salt  -  •  0'067 
Humus,  soluble  in  alkalies  •  *•• '  0'540 
Humus  -  -  -  .»f  *  •  1*500 

100-000 

This  soil  is  improved  by  gypsum.  Its 
sterility  is  due  to  the  excessive  quantity  of 
carbonate  of  soda  which  is  present. 

NORTH    AMERICA. 

46.  Surface-soil  of  alluvial  land  in  Ohio, 
remarkable  for  its  great  fertility.     100  parts 
consisted  of: — 

Silica  and  fine  siliceous  sand  •  •  79'538 

Alumina,  ....  7'306 
Peroxide  and  protoxide  of  iron,  (much 

magnetic  iron  sand)  ...  5'824 

Peroxide  of  manganese  -  -  1*320 

Lime  .....  Q'619 

Magnesia  ....  T024 

Potash,  principally  combined  with  silica  0*200 

Soda  .  .  .  0024 
Phosphoric  acid  combined  with  lime  and 

oxirle  of  iron  -  -  .  1'776 

Sulphuric  acid,  combined  with  lime  -  0'122 

Chlorine  -  0  Q36 


lOO'OOO 

47.  (A.)  Surface-soil  of  a  mountainous 
district  in  the  neighbourhood  of  Ohio.  (B.) 
Analysis  of  the  subsoil,  This  soil  is  also 
distinguished  for  its  great  fertility.  100  parts 
contain : — 


(B) 

94261 
1*376 
2-336 
1*200 
0.243 
0-310 

0-240 

a  trace 

0-034 

a  trace 


(A) 

Silica,  with  fine  siliceous  sand  -  87*143 
Alumina  -----  5*666 
Peroxide  and  protoxide  of  iron  -  2'220 
Peroxide  of  manganese  -  -  0*360 

Lime  -  -  -  0*564 

Magnesia  -  -  -    0*312 

Potash,  principally  combined  with 

silica  0*120 

Soda        -  ...     0-025 

Phosphoric  acid        -  -          0*060 

Sulphuric  acid  •  *•  «  0027 
Chlorine  -  0*036 

Humus  soluble  in  alkalies  1.304 

Humus  ....         1-Q72 

Carbonic  acid,  combined  with  lime  0*080 
Nitrogenous  organic  matter  -  1*011 

100-000   100-000 

In  the  preceding  part  of  the  chapter  we 
have  inserted  a  number  of  analyses  of  vari- 
ous soils,  as  well  as  the  conclusions  deduced 
from  them,  by  means  of  which  the  farmer 
may  be  enabled  to  ascertain  the  manures 
best  adapted  for  each  variety  of  soil.  By  in- 
specting the  analyses  of  the  sterile  soils,  it 
will  be  apparent  that  it  is  in  the  power  of 
chemistry  to  point  out  the  causes  of  their 
sterility.  The  general  cause  which  con- 
duces to  the  sterility  of  soils  is  either  the  ab- 
sence of  certain  constituents  indispensable 
for  the  growth  of  plants,  or  the  presence 
of  others  which  exert  an  injurious  or  poi- 
sonous action.  The  analyses  are  those  of 
Dr.  Sprengel, — a  chemist  who  has  unceas- 
ingly occupied  himself  for  the  last  twenty 
years  in  endeavouring  to  point  out  the  im- 
portance of  the  inorganic  ingredients  of  a 
soil  for  the  developement  of  plants  cultivated 
upon  it.  He  considers  as  essential  all  the 
inorganic  bodies  found  in  the  ashes  of  plants. 
Now,  although  we  cannot  coincide  with  him 
in  the  opinion  that  iron  and  manganese  are 
indispensable  for  vegetable  life,  (for  these 
bodies  are  found  as  excrementitious  matter 
only  in  the  bark,  and  never  form  a  constitu- 
ent of  an  organ,)  yet  we  gratefully  acknow- 
ledge the  valuable  services  which  he  has  ren- 
dered to  agriculture,  by  furnishing  a  natural 
explanation  of  the  action  of  ashes,  marl,  &c., 
in  the  improvement  of  a  soil.  Sprengel  has 
shown  that  these  mineral  manures  af- 
ford to  a  soil  alkalies,  phosphates,  and  sul- 
phates ;  and  further,  that  they  can  exert  a 
notable  influence  only  on  those  soils  in 
which  they  are  absent  or  deficient.  In  a 
former  chapter  of  this  book  I  have  endea- 
voured to  point  out  the  importance  of  consi- 
dering these  constituents  as  intimately  con- 
nected with  the  vital  processes  of  the  vege- 
table organism,  and  have  shown  that  the 
different  families  of  plants  contain  unequal 


84 


AGRICULTURAL   CHEMISTRY. 


quantities  of  inorganic  ingredients.  This 
subject  has  been  left  unexamined  by  Spren- 
gel,  yet  it  is  one  of  much  importance ;  for 
the  application  of  manures  must  be  regulated 
by  the  composition  of  the  plants  which  are 
cultivated  on  any  particular  soil.  Still  the 
composition  of  the  soil  must  always  be  kept 
in  view.  Thus  it  would  be  perfect  extrava- 
gance to  manure  certain  soils  with  marl, 
ashes,  or  gypsum ;  whilst,  on  the  contrary, 
these  compounds  would  produce  the  most 
beneficial  results  on  other  lands. 

In  a  former  part  of  the  work,  the  princi- 
pal action  of  gypsum  upon  vegetation  was 
ascribed  to  the  decomposition  and  fixation 
of  the  carbonate  of  ammonia  contained  in 
rain-water;  but  gypsum  exerts  a  twofold 
action.  The  power  of  decomposing  car- 
bonate of  ammonia,  and  of  fixing  the  am- 
monia, is  not  peculiar  to  gypsum,  but  is 
shared  also  by  other  salts  of  lime  (chloride 


of  calcium,  for  example.)  But  it  acts  also 
as  a  sulphate,  and  when  useful  as  such  can- 
not be  replaced  by  any  other  salt  of  lime 
which  does  not  contain  sulphuric  acid. 

Hence  gypsum  can  be  replaced  as  a  ma- 
nure only  by  a  mixture  of  a  salt  of  lime 
with  ammonia,  and  a  salt  of  sulphuric  acid. 
Sulphate  of  ammonia  can  therefore  be  sub- 
stituted for  gypsum,  and  exerts  a  more  rapid 
and  effectual  action.  In  France,  sulphuric 
acid  has  been  poured  upon  the  fields  after 
the  removal  of  the  crops,  and  has  been 
found  to  form  a  good  manuie.  But  this  is 
merely  a  process  for  forming  gypsum  in 
situ ;  for  the  soils  upon  which  it  is  applied 
contain  much  lime,  which  enters  into  com- 
bination with  the  sulphuric  acid.  It  would 
certainly  be  much  more  advantageous  to 
form  sulphate  of  ammonia  by  adding  the 
acid  to  putrefied  urine,  and  to  apply  this 
mixture  to  the  field. 


APPENDIX  TO  PART  I. 


EXPERIMENTS  AND  OBSERVATIONS  ON  THE  ACTION  OF  CHARCOAL  FROM 
WOOD  ON  VEGETATION.— BY  EDWARD  LUKAS.* 


"  IN  a  division  of  a  low  hot-house  in  the 
botanical  garden  at  Munich,  a  bed  was  set 
apart  for  young  tropical  plants,  but  instead 
of  being  filled  with  tan,  as  is  usually  the 
rase,  it  was  filled  with  the  powder  of  char- 
coal fy.  rrwfria.-.  "vhich  could  be  easily  pro- 
cured,) tne  Aarge  pieces  of  charcoal  having 
been  previously  separated  by  means  of  a 
sieve.  The  heat  was  conducted  by  means 
of  a  tube  of  white  iron  into  a  hollow  space 
in  thjs  bed,  and  distributed  a  gentle  warmth, 
such  as  tan  communicates,  when  in  a  state 
of  fermentation.  The  plants  placed  in  this 
bed  of  charcoal  quickly  vegetated,  and  ac- 
quired a  healthy  appearance.  Now,  as  is 
always  the  case  in  such  beds,  the  roots  of 
many  of  the  plants  penetrated  through 
the  holes  in  the  bottom  of  the  pots,  and 
then  spread  themselves  out ;  but  these 
plants  evidently  surpassed  in  vigour  and 
general  luxuriance  plants  grown  in  the 
common  way — for  example,  in  tan.  Seve- 
ral of  them,  of  which  I  shall  only  specify 
the  beautiful  TJmnbergia  alata,  and  the  ge- 
nus Peireskice,  throve  quite  astonishingly; 
the  blossoms  of  the  former  were  so  rich, 
that  all  who  saw  it  affirmed  they  had  never 
before  seen  such  a  specimen.  It  produced 
a  l*o  a  number  of  seeds  without  any  artificial 
aid,  while  in  most  cases  it  is  necessary  to 
apply  the  pollen  by  the  hand.  The  Peires- 
kice  grew  so  vigorously,  that  the  P.  aculeata 
produced  shoots  several  ells  in  length,  and  the 
P.  grandifolia  acquired  leaves  a  foot  in  length. 
These  facts,  as  well  as  the  quick  germina- 
tion of  the  seeds  which  had  been  scattered 
spontaneously,  and  the  abundant  appearance 
of  young  Filices,  naturally  attracted  my  at- 
tention, and  I  was  gradually  led  to  a  series 

*  See  page  27. 


of  experiments,  the  results  of  which  may 
not  be  uninteresting ;  for,  besides  being  of 
practical  use  in  the  cultivation  of  most 
plants,  they  demonstrate  also  several  facts 
of  importance  to  physiology.  The  first  ex- 
periment which  naturally  suggested  itself 
was  to  mix  a  certain  proportion  of  charcoal 
with  the  earth  in  whicn  different  plants 
grew,  and  to  increase  its  quantity  according 
as  the  advantage  of  the  method  was  per- 
ceived. An  addition  of  f  charcoal,  for  exam- 
ple, to  vegetable  mould,  appeared  to  answer 
excellently  for  the  Gesnena  and  Gloxinia, 
and  also  for  the  tropical  Jlroidece,  with  tube- 
rous roots.  The  first  two  soon  excited  the 
attention  of  connoisseurs,  by  the  great 
beauty  of  all  their  parts  and  their  general 
appearance.  They  surpassed  very  quickly 
those  cultivated  in  the  common  way,  both 
in  the  thickness  of  their  stems  and  dark 
colour  of  their  leaves  ;  their  blossoms  were 
beautiful,  and  their  vegetation  lasted  much 
longer  than  usual,  so  much  so,  that  in  the 

|  middle  of  November,  when  other  plants  of 
the  same  kinds  were  dead,  these  were  quite 
fre'sh  and  partly  in  bloom.  Jlroidece  took 
root  very  rapidly,  and  their  leaves  surpassed 
much  in  size  the  leaves  of  those  not  so 
treated;  the  species  which  are  reared  as 
ornamental  plants  on  account  of  the  beauti 
ful  colouring  of  their  leaves,  (I  mean  such 
as  the  Caladium  bicolor,  Pictum,  Pcecile, 
&c.,)  were  particularly  remarked  for  the 
liveliness  of  their  tints  ;  and  it  happened 
here  also,  that  the  period  of  their  vegetation 

I  was  unusually  long.     A  cactus  planted  in  a 

!  mixture  of  equal  parts  of  charcoal  and  earth 
throve  progressively,  and  attained  double  of 
its  former  size  in  the  space  of  a  few  weeks. 

.  The  use  of   the  charcoal  was  very  advan- 


APPENDIX  TO   PART   I. 


85 


tageous  with  several  of  the  Bromeliacece,  and 
Lilacece,  with  the  Citrus,  and  Begonia  also, 
and  even  with  the  Palmes.  The  same  ad- 
vantage was  found  in  the  case  of  almost  all 
those  plants  for  which  sand  is  used,  in  order 
to  keep  the  earth  porous,  when  charcoal  was 
mixed  with  the  soil  instead  of  sand;  the 
vegetation  was  always  rendered  stronger  and 
more  vigorous. 

"  At  the  same  time  that  these  experiments 
were  performed  with  mixtures  of  charcoal 
with  different  soils,  the  charcoal  was  also 
used  free  from  any  addition,  and  in  this  case 
the  best  results  were  obtained.  Cuts  of 
plants  from  different  genera  took  root  in  it 
well  and  quickly;  I  mention  here  only  the 
Euphorbia  fastuosa  and  fulgens  which  took 
root  in  ten  days,  Pandanus  utilis  in  three 
months,  P.  amaryllifolius,  Chamcedorea  ela- 
tior  in  four  weeks,  Piper  nigrum,  Begonia, 
Ficus,  Cecropia,  Chiococca,  Buddleya,  Hakea, 
Phyllanthus,  Capparis,  Launts,  Stifftia,  Joe- 
quinia,  Mimosa,  Cactus,  in  from  eight  to  ten 
aays,  and  several  others  amounting  to  forty 
species,  including  Ilex,  and  many  others. 
Leaves,  and  pieces  of  leaves,  and  even  pe- 
dunculi,  or  petioles,  took  root  and  in  part 
budded  in  pure  charcoal.  Amongst  others 
we  may  mention  thefoliola  of  several  of  the 
Cycadece  as  having  taken  root,  as  also  did 
parts  of  the  leaves  of  the  Begonia  Telfairice, 
and  Jacaranda  brasiliensis ;  leaves  of  the 
Euphorbia  fastuosa,  Oxalis  Barrilieri,  Ficus, 
Cyclamen,  Polyanthes,  Mesembryanthemum ; 
also  the  delicate  leaves  of  the  Lophospermum 
and  Martynia,  pieces  of  a  leaf  of  the  Jlgave 
americana;  tufts  of  Pinus,  &c.;  and  all  with- 
out the  aid  of  a  previously  formed  bud. 

"  Pure  charcoal  acts  excellently  as  a 
means  of  curing  unhealthy  plants.  A  Do- 
rianthes  excelsa,  for  example,  which  had 
been  drooping  for  three  years,  was  rendered 
completely  healthy  in  a  very  short  time  by 
this  means.  An  orange-tree  which  had  the 
very  common  disease  in  which  the  leaves 
become  yellow,  acquired  within  four  weeks 
its  healthy  green  colour,  when  the  upper 
surface  of  the  earth  was  removed  from  the 
pot  in  which  it  was  contained,  and  a  ring 
of  charcoal  of  an  inch  in  thickness  strewed 
in  its  place  around  the  periphery  of  the  pot. 
The  same  was  the  case  with  the  Gardenia. 

"  I  should  be  led  too  far  were  I  to  state  all 
the  results  of  the  experiments  which  I  have 
made  with  charcoal.  The  object  of  this 
paper  is  merely  to  show  the  general  effect 
exercised  by  this  substance  on  vegetation  ; 
but  the  reader  who  takes  particular  interest 
in  the  subject  will  find  more  extensive  ob- 
servations in  the  'Jlttgemeine  Deutsche  Garten- 
zeitung'  of  Otto  and  Dietrich,  in  Berlin;  or 
Loudon's  Gardener's  Magazine  for  March, 
1841. 

"  The  charcoal  employed  in  these  experi- 
ments was  the  dust-like  powder  of  charcoal 
from  firs  and  pines,  such  as  is  used  in  the 
forges  of  blacksmiths,  and  may  be  easily 
procured  in  any  quantity.  It  was  found  to 


have  most  effect  when  allowed  to  lie  during 
the  winter  exposed  to  the  action  of  the  air. 
In  order  to  ascertain  the  effects  of  different 
kinds  of  charcoal,  experiments  were  also 
made  upon  that  obtained  from  the  hard 
woods  and  peat,  and  also  upon  animal  char- 
coal, although  I  foresaw  the  probability  that 
none  of  them  would  answer  so  well  as  that 
of  pine-wood,  both  on  account  of  its  porosity 
and  the  ease  with  which  it  is  decomposed.* 

"  It  is  superfluous  to  remark,  that  in  treat- 
ing plants  in  the  manner  here  described,  they 
must  be  plentifully  supplied  with  water, 
since  the  air  having  such  free  access  pene- 
trates and  dries  the  roots,  so  that  unless  this 
precaution  is  taken,  the  failure  of  all  such 
experiments  is  unavoidable. 

"  The  action  of  charcoal  consists  primarily 
in  its  preserving  the  parts  of  the  plants  with 
which  it  is  in  contact — whether  they  be 
roots,  branches,  leaves,  or  pieces  of  leaves 
— unchanged  in  their  vital  power  for  a  long 
space  of  time,  so  that  the  plant  obtains  time 
to  develope  the  organs  which  are  necessary 
for  its  further  support  and  propagation. 
There  can  scarcely  be  a  doubt  also  that  the 
charcoal  undergoes  decomposition ;  for  after 
being:  used  five  to  six  years  it  becomes  a 
coaly  earth;  and  if  this  is  the  case,  it  must 
yield  carbon,  or  carbonic  oxide,  abundantly 
to  the  plants  growing  in  it,  and  thus  afford 
the  principal  substance  necessary  for  the 
nutrition  of  vegetables.!  In  what  other 
manner  indeed  can  we  explain  the  deep 
green  colour  and  great  luxuriance  of  the 
leaves  and  every  part  of  the  plants,  which 
can  be  obtained  in  no  other  kind  of  soil,  ac- 
cording to  the  opinion  of  men  well  qualified 
to  judge?  It  exercises  likewise  a  favourable 
influence  by  decomposing  and  absorbing  the 
matters  excreted  by  the  roots,  so  as  to  keep 
the  soil  free  from  the  putrefying  substances 
which  are  often  the  cause  of  the  death  of  the 
spongiolce.  Its  porosity,  as  well  as  the  power 
which  it  possesses  01  absorbing  water  with 
rapidity,  and,  after  its  saturation,  of  allow- 
ing all  other  water  to  sink  through  it,  are 
causes  also  of  its  favourable  effects.  These 
experiments  show  what  a  close  affinity  the 
component  parts  of  charcoal  have  to  all 
plants,  for  every  experiment  was  crowned 
with  success,  although  plants  belonging  to  a 

*  M.  Lukas  has  recently  repeated  these  experi- 
ments, and  found  that  the  animal  charcoal  ob- 
tained by  the  calcination  of  bones  possesses  a  de- 
cided advantage  over  all  other  kinds  of  charcoal, 
which  he  subjected  to  experiment. — Liebig1  s  An- 
nalen,  Sand  xxxix.  Heft  I.  S.  127. 

t  As  some  misconception  has  arisen  regarding 
this  explanation  of  the  action  of  charcoal  upon  ve- 
getation, and  an  idea  propagated  that  the  intro- 
duction of  these  opinions  into  this  work  incorpo- 
rated them  with  those  of  Liebig,  it  is  necessary  to 
state  that  they  are  merely  inserted  here  as  part  of 
the  papers  of  M.  Lukas.  The  true  explanation 
has  been  given  in  a  former  part  of  the  work,  viz., 
that  charcoal  possesses  the  power  of  absorbing 
carbonic  acid  and  ammonia  from  the  atmosphere, 
which  serve  fo;  the  nourishment  of  plants. — ED. 


86 


AGRICULTURAL   CHEMISTRY. 


great  many  different  families  were  subjected 
to  trial."  (Bnchner's  Repertorium,  ii.  Reihe, 
xix.  Bd.  S.  38.) 

ON    A   MODE    OF    MANURING   VINES. 

The  observations  contained  in  the  follow- 
ing pages  should  be  extensively  known,  be- 
cause they  furnish  a  remarkable  proof  of  the 
principles  which  have  been  stated  in  the 
preceding  part  of  the  work,  both  as  to  the 
manner  in  which  manure  acts,  and  on  the 
origin  of  the  carbon  and  nitrogen  of  plants. 

They  prove  that  a  vineyard  may  be  re- 
tained in  fertility  without  the  application 
of  animal  matters,  when  the  leaves  and 
branches  pruned  from  the  vines  are  cut  into 
small  pieces  and  used  as  manure.  According 
to  the  first  of  the  following  statements,  both 
of  which  merit  complete  confidence,  the 
perfect  fruitfulness  of  a  vineyard  has  been 
maintained  in  this  manner  for  eight  yeans, 
and  according  to  the  second  statement  for 
ten  years. 

Now,  during  this  long  period,  no  carbon 
was  conveyed  to  the  soil,  for  that  contained 
in  the  pruned  branches  was  the  produce  of 
the  plant  itself,  so  that  the  vines  were  placed 
exactly  in  the  same  condition  as  trees  in  a 
forest  which  received  no  manure.  Under 
ordinary  circumstances  a  manure  containing 
potash  must  be  used,  otherwise  the  fertility 
of  the  soil  will  decrease.  This  is  done  in  all 
wine-countries,  so  that  alkalies  to  a  very 
considerable  amount  must  be  extracted  from 
the  soil. 

When,  however,  the  method  of  manuring 
now  to  be  described  is  adopted,  the  quantity 
of  alkalies  exported  in  the  wine  does  nor 
exceed  that  which  the  progressive  disinte- 
gration of  the  soil  every  year  renders  capable 
of  being  absorbed  by  the  plants.  On  the 
Rhine  1  litre  of  wine  is  calculated  as  the 
yearly  produce  of  a  square  metre  of  land 
(10-8  square  feet  English.)  Now  if  we 
suppose  that  the  wine  is  three-fourths  satu- 
rated with  cream  of  tartar,  a  proportion 
much  above  the  truth,  then  we  remove  from 
every  square  metre  of  land  with  the  wine 
only  1-8  gramme  of  potash.  1000  grammes 
(i  litre)  of  champagne  yield  only  1.54,  and 
the  same  quantity  of  Wachenheimer  1*72 
of  a  residue  which  after  being  heated  to  red- 
ness is  found  to  consist  of  carbonates. 

One  vine-stock,  on  an  average,  grows  on 
every  square  metre  of  land,  and  1000  parts 
of  the  pruned  branches  contain  56  to  60 
parts  of  carbonate,  or  38  to  40  parts  of  pure 
potash.  Hence  it  is  evident  that  45  grammes, 
or  1  ounce,  of  these  branches  contain  as 
much  potash  as  1000  grammes  (1  litre)  of 
wine.  But  from  ten  to  twenty  times  this 
quantity  of  branches  are  yearly  taken  from 
the  above  extent  of  surface. 

In  the  vicinity  of  Johannisberg,  Rudes- 
heim,  and  Budesheim,  new  vines  are  not 
planted  after  the  rooting  out  of  the  old  stocks, 
until  the  land  has  lain  for  five  or  six  years  in 


barley  and  esparcet,  or  lucerne;  in  the  sixth 
year  the  young  slocks  are  planted,  but  not 
manured  till  the  ninth. 


ON    THE    MANURING    OF    THE    SOIL    IN    VINE- 
YARDS.* 

"  In  reference  to  an  article  in  your  paper, 
No.  7,  1838,  and  No.  29,  1839,  I  cannot 
omit  the  opportunity  of  again  calling  the 
public  attention  to  the  fact,  that  nothing 
more  is  necessary  for  the  manure  of  a  vine- 
yard than  the  branches  which  are  cut  from 
the  vines  themselves. 

"  My  vineyard  has  been  manured  in  this 
way  for  eight  years,  without  receiving  any 
other  kind  of  manure,  and  yet  more  beauti- 
ful and  richly  laden  vines  could  scarcely  be 
pointed  out.  I  formerly  followed  the  method 
usually  practised  in  this  district,  and  was 
obliged  in  consequence  to  purchase  manure 
to  a  large  amount.  This  is  now  entirely 
saved,  and  my  land  is  in  excellent  condition. 

"  When  I  see  the  fatiguing  labour  used 
in  the  manuring  of  vineyards — horses  and 
men  toiling  up  the  mountains  with  unne- 
cessary materials — I  feel  inclined  to  say  to 
all,  Come  to  my  vineyard  and  see  how  a 
bountiful  Creator  has  provided  that  vines 
shall  manure  themselves,  like  the  trees  in  a 
forest,  and  even  better  than  they!  The 
foliage  falls  from  trees  in  a  forest,  only 
when  they  are  withered,  and  they  lie  for 
years  before  they  decay;  but  the  branches 
are  pruned  from  the  vine  in  the  end  of  July 
or  beginning  of  August  whilst  still  fresh  and 
moist.  If  they  are  then  cut  into  small  pieces 
and  mixed  wiu  the  earth,  they  undergo 
putrefaction  so  completely,  that,  as  I  have 
learned  by  experience,  at  the  end  of  four 
weeks  not  the  smallest  trace  of  them  can  be 
found." 

"  REMARKS  OF  THE  EDITOR. — We  find 
the  following  notices  of  the  same  fact  in 
Henderson's  «  Geschichte  der  Weine  dt.r 
alteiLund  neuen,  Zeit:' — 

"  *  The  best  manure  for  vines  is  the 
branches  pruned  from  the  vines  themselves, 
cut  into  small  pieces,  and  immediately  mixed 
with  the  soil.' 

"These  branches  were  used  as  manure 
long  since  in  the  Bergstrasse.  M.  Frauen- 
felder  says:f 

"  *  I  remember  that  twenty  years  ago,  a 
man  called  Peter  Muller  had  a  vineyard 
here  which  he  manured  with  the  branches 
pruned  from  the  vines,  and  continued  this 
practice  for  thirty  years.  His  way  of  apply- 
ing them  was  to  hoe  them  into  the  soil  alter 
having  cut  them  into  small  pieces. 

"  *  His  vineyard  was  always  in  a  thriving 


'  Slightly  abridged  from  an  article  by  M.  Krebi 
of  Seeheim,  in  the  "  Zeitschrift  fur  die  landwirth- 
schaftlichen  Vereine  des  Grosherzogthums  Hes- 
sen."  No.  28,  July  9,  1840. 

t  Badisches  landwirthschaftliches  Wochenblatt. 
v.  1834,  S.  52  and  79. 


CHEMICAL   TRANSFORMATIONS. 


87 


condition;  so  much  so  indeed,  that  the  pea- 
sants here  speak  of  it  to  this  day,  wondering 
that  old  Miiller  had  so  good  a  vineyard,  and 
yet  used  no  manure.7 

"  Lastly,  Wilhelm  Ruf  of  Schriesheim 
writes : 

•'* s  For  the  last  ten  years  I  have  been 
unable  to  place  dung  on  my  vineyard,  be- 
cause I  am  poor  and  can  buy  none.  But  I 
was  very  unwilling  to  allow  my  vines  to 
decay,  as  they  are  my  only  source  of  sup- 
port in  my  old  age;  and  I  often  walked  very 
anxiously  amongst  them,  without  knowing 
what  I  should  do.  At  last  my  necessities 
became  greater,  which  made  me  more  at- 
tentive, so  that  I  remarked  that  the  grass 
was  longer  on  some  spots  where  the  branches 
of  the  vine  fell  than  on  those  on  which  there 
were  none.  So  I  thought  upon  the  matter, 


and  then  said  to  myself:  If  these  branches 
can  make  the  grass  large,  strong,  and  green, 
they  must  also  be  able  to  make  my  plants 
grow  better,  and  become  strong  and  green. 
I  dug  therefore  my  vineyard  as  deep  as  if  I 
would  put  dung  into  it,  and  cut  the  branches 
into  pieces,  placing  them  in  the  holes  and 
covering  them  with  earth.  In  a  year  I  had 
the  very  great  satisfaction  to  see  my  barren 
vineyard  become  quite  beautiful.  This  plan 
I  continued  every  year,  and  now  my  vines 
grow  splendidly,  and  remain  the  whole 
summer  green,  even  in  the  greatest  heat. 

"  'All  my  neighbours  wonder  very  much 
how  my  vineyard  is  so  rich,  and  that  I  ob- 
tain so  many  grapes  from  it,  and  yet  they 
all  know  that  I  have  put  no  dung  upon  it 
for  ten  years.'  " 


PART  II. 


OF  THE  CHEMICAL  PROCESSES  OF  FERMENTATION,  DECAY  AND  PUTRE. 

FACTION. 


CHAPTER  1. 

CHEMICAL    TRANSFORMATIONS. 

WOODY  fibre,  sugar,  gum,  and  all  such 
organic  compounds,  surfer  certain  changes 
when  in  contact  with  other  bodies,  that  is, 
they  suffer  decomposition. 

There  are  two  distinct  modes  in  which 
these  decompositions  take  place  in  organic 
chemistry. 

When  a  substance  composed  of  two  com- 
pound bodies,  crystallized  oxalic  acid  for 
example,  is  brought  in  contact  with  concen- 
trated sulphuric  acid,  a  complete  decompo- 
sition is  effected  upon  the  application  of  a 
gentle  heat.  Now  crystallized  oxalic  acid 
is  a  combination  of  water  with  the  anhy- 
drous acid;  but  concentrated  sulphuric  acid 
possesses  a  much  greater  affinity  for  water 
than  oxalic  acid,  so  that  it  attracts  all  the 
water  of  crystallization  from  that  substance. 
In  consequence  of  this  abstraction  of  the 
water,  anhydrous  oxalic  acid  is  set  free ;  but 
as  this  acid  cannot  exist  in  a  free  state,  a 
division  of  its  constituents  necessarily  en- 
sues, by  which  carbonic  acid  and  carbonic 
oxide  are  produced,  and  evolved  in  the 
gaseous  form  in  equal  volumes.  In  this 
example,  the  decomposition  is  the  conse- 
quence of  the  removal  of  two  constituents 
(the  elements  of  water,)  which  unite  with 
me  sulphuric  acid,  and  its  cause  is  the  supe- 
rior affinity  of  the  acting  body  (the  sulphuric 
acid)  for  water.  In  consequence  of  the  re- 
moval of  the  component  parts  of  water,  the 
remaining  elements  enter  into  a  new  form ; 
in  place  of  oxalic  acid,  we  have  its  elements 
in  the  form  of  carbonic  acid  and  carbonic 
oxide. 

This  form  of  decomposition,  in  which  the 
change  is  effected  by  the  agency  of  a  body 


which  unites  with  one  or  more  of  the  con- 
stituents of  a  compound,  is  quite  analogous 
to  the  decomposition  of  inorganic  substances. 
When  we  bring  sulphuric  acid  and  nitrate 
of  potash  together,  nitric  acid  is  separated 
in  consequence  of  the  affinity  of  sulphuric 
acid  for  potash ;  in  consequence,  therefore, 
of  the  formation  of  a  new  compound  (sul- 
phate of  potash.) 

In  the  second  form  of  these  decomposi- 
tions, the  chemical  affinity  of  the  acting 
body  causes  the  component  parts  of  the 
body  which  is  decomposed  to  combine  so  as 
to  form  new  compounds,  of  which  either 
both,  or  only  one,  combine  with  the  acting 
body.  Let  us  take  dry  wood,  for  example, 
anc1  moisten  it  with  sulphuric  acid  ;  after  a 
short  time  the  wood  is  carbonised,  while  the 
sulphuric  acid  remains  unchanged,  with  the 
exception  of  its  being  united  with  more 
water  than  it  possessed  before.  Now  this 
water  did  not  exist  as  such  in  the  wood, 
although  its  elements,  oxygen  and  hydro- 
gen, were  present ;  but  by  the  chemical  at- 
traction of  sulphuric  acid  for  water,  they 
were  in  a  certain  measure  compelled  to  unite 
in  this  form;  and  in  consequence  of  this,  the 
carbon  of  wood  was  separated  as  charcoal. 

Hydrocyanic  acid,  and  water,  in  contact 
with  hydrochloric  acid,  are  mutually  decom- 
posed. The  nitrogen  of  the  hydrocyanic 
acid,  and  a  certain  quantity  of  the  hydrogen 
of  the  water,  unite  together  and  form  am- 
monia; whilst  the  carbon  and  hydrogen  of 
the  hydrocyanic  acid  combine  with  the  oxy- 
gen of  the  water,  and  form  formic  acid.  The 
ammonia  combines  with  the  muriatic  acid. 
Here  the  contact  of  muriatic  acid  with  water 
and  hydrocyanic  acid  causes  a  disturbance 
in  the  attraction  of  the  elements  of  both 
compounds,  in  consequence  of  which  they 
arrange  themselves  into  new  combinations, 


88 


AGRICULTURAL   CHEMISTRY. 


one    of   which — ammonia — possesses    the  j  an  alloy  of  copper,  zinc,  and  nickel,  dis- 
power  of  uniting  with  the  acting  body.          j  solves  easily  in  this  acid  with  evolution  of 

Inorganic  chemistry  can  present  instances    hydrogen  gas. 

analogous  to  this  class  of  decomposition  !  Tin  decomposes  nitric  acid  with  great  fa- 
also;  but  there  are  forms  of  organic  chemi-  cility,  but  water  with  difficulty;  and  yet, 
cal  decomposition  of  a  very  different  kind,  when  tin  is  dissolved  in  nitric  acid,  hydrogen 
in  which  none  of  the  component  parts  of  the  |  is  evolved  at  the  same  time,  from  a'decom- 
matter  which  suffers  decomposition  enter  j  position  of  the  water  contained  in  the  acid 
into  combination  with  the  body  which  de-  ! 
termines  the  decomposition.  In  cases  of 


this  kind  a  disturbance  is  produced  in  the 
mutual  attraction  of  the  elements  of  a  com- 
pound, and  they  in  consequence  arrange 
themselves  into  one  or  several  new  combi- 
nations, which  are  incapable  of  suffering 
farther  change  under  the  same  conditions. 

When,  by  means  of  the  chemical  affinity 
of  a  second  body,  by  the  influence  of  heat, 
or  through  any  other  causes,  the  composi- 
tion of  an  organic  compound  is  made  to 
undergo  such  a  change,  that  its  elements 
form  two  or  more  new  compounds,  tnis 
manner  of  decomposition  is  called  a  chemi- 
cal transformation  or  metamorphosis.  It  is 
an  essential  character  of  chemical  transfor- 
mations, that  none  of  the  elements  of  the 
body  decomposed  are  singly  set  at  liberty. 

The  changes,  which  are  designated  by  the 
terms  fermentation,  decay,  and  putrefaction, 
are  chemical  transformations  effected  by  an 
agency  which  has  hitherto  escaped  atten- 
tion, but  the  existence  of  which  will  be 
proved  in  the  following  pages. 


CHAPTER  II 


ON   THE  CAUSES  WHICH    EFFECT    FERMENTA- 
TION, DECAY,*  AND  PUTREFACTION. 

ATTENTION  has  been  recently  directed  to 
the  fact,  that  a  body  in  the  act  of  combina- 
tion or  decomposition  exercises  an  influence 
upon  any  other  body  with  which  it  may  be 
in  contact.  Platinum,  for  example,  does 
not  decompose  nitric  acid  ;  it  may  be  boiled 
with  this  acid  without  being  oxidized  by  it, 
even  when  in  a  state  of  such  fine  division, 
that  it  no  longer  reflects  light  (black  spongy 
platinum.)  But  an  alloy  of  silver  and  pla- 
tinum dissolves  with  great  ease  in  nitric 
acid ;  the  oxidation  which  the  silver  suffers 
causes  the  platinum  to  submit  to  the  same 
change;  or,  in  other  words,  the  latter  body, 
from  its  contact  with  the  oxidizing  silver, 
acquires  the  property  of  decomposing  nitric 
acid. 


and  ammonia  is  formed  in  addition  to  oxide 
of  tin. 

In  the  examples  here  given  the  only  com- 
bination or  decomposition  which  can  be  ex- 
plained by  chemical  affinity  is  the  last.  In 
the  other  cases,  electrical  action  ought  to 
have  retarded  or  prevented  the  oxidation  of 
the  platinum  or  copper  while  they  were  in 
contact  with  silver  or  zinc,  but,  as  experience 
shows,  the  influence  of  the  opposite  electri- 
cal conditions  is  more  than  counterbalanced 
by  chemical  actions. 

The  same  phenomena  are  seen  in  a  less 
dubious  form  in  compounds,  the  elements 
of  which  are  held  together  only  by  a  feeble 
affinity.  It  is  well  known  that  there  are 
chemical  compounds  of  so  unstable  a  nature, 
that  changes  in  temperature  and  electrical 
condition,  or  even  simple  mechanical  fric- 
tion, or  contact  with  bodies  of  apparently 
totally  indifferent  natures,  cause  such  a  dis- 
turbance in  the  attraction  of  their  constituents, 
that  the  latter  enter  into  new  forms,  with- 
out any  of  them  combining  with  the  acting 
body.  These  compounds  appear  to  stand 
but  just  within  the  limits  of  chemical  combi- 
nation, and  agents  exercise  a  powerful  influ- 
ence over  them,  which  are  completely  de- 
void of  action  on  compounds  of  a  stronger 
affinity.  Thus,  by  a  slight  increase  of  tem- 
perature, the  elements  of  hypochlorous  acid 
separate  from  one  another  with  evolution  of 
heat  and  light;  chloride  of  nitrogen  explodes 
by  contact  with  many  bodies,  which  com- 
bine neither  with  chlorine  nor  nitrogen  at 
common  temperatures  ;  and  the  contact  of 
any  solid  substance  is  sufficient  to  cause  the 
explosion  of  iodide  of  nitrogen,  or  fulminat- 
ing silver. 

It  has  never  been  supposed  that  the  causes 
of  the  decomposition  of  these  bodies  should 
be  ascribed  to  a  peculiar  power,  different 
from  that  which  regulates  chemical  affinity, 
a  power  which  mere  contact  with  the  down 
of  a  feather  is  sufficient  to  set  in  activity, 
and  which,  once  in  action,  gives  rise  to 
the  decomposition.  These  substances  have 
always  been  viewed  as  chemical  compounds 
of  a  very  unstable  nature,  in  which  the 
component  parts  are  in  a  state  of  such  ten- 


Copper  does  not  decompose  water,  even    sjon)  that  the  least  disturbance  overcomes 
when  boiled  in  dilute  sulphuric  acid ;  but  |  their  chemical  affinity.     They  exist  only  by 

the  vis  inertise,  and  any  shock  or  movement 
is  sufficient  to  destroy  the  attraction  of  their 
component  parts,  and  consequently  their 
existence  in  their  definite  form. 

Peroxide  of  hydrogen  belongs  to  this  class 
of  bodies ;  it  is  decomposed  by  all  substances 
capable  of  attracting  oxygen  from  it,  and 


*  An  essential  distinction  is  drawn  in  the  follow- 
ing part  of  the  work,  between  decay  and  putre- 
faction (Verwesung  und  Faulniss,)  and  they  are 
shown  to  depend  on  different  causes ;  but  as  the 
word  decay  is  not  generally  applied  to  a  distinct 
species  of  decomposition,  and  does  not  indicate  its 
true  nature,  1  shall  in  future,  at  the  suggestion  of  •  . 

he  author!   employ  the  term  eremacansis,  the    even  by  contact  with  many  bodies,  such  as 
meaning  of  which  has  been  already  explained.— ED.  !  platinum  or  silver,  which  do  not  enter  into 


CHEMICAL  TRANSFORMATIONS. 


combination  with  any  of  its  constituents. 
In  this  respect,  its  decomposition  depends 
evidently  upon  the  same  causes  which  effect 
that  of  iodide  of  nitrogen,  or  fulminating 
silver.  Yet  it  is  singular  that  the  cause  of 
the  sudden  separation  of  the  component 
parts  of  peroxide  of  hydrogen  has  been 
viewed  as  different  from  those  of  common  de- 
composition, and  has  been  ascribed  to  a  new 
power  termed  the  catalytic  force.  Now,  it 
has  not  been  considered,  that  the  presence 
of  the  platinum  and  silver  serves  here  only 
to  accelerate  the  decomposition ;  for  without 
the  contact  of  these  metals,  the  peroxide  of 
hydrogen  decomposes  spontaneously,  al- 
though very  slowly.  The  sudden  separa- 
tion of  the  constituents  of  peroxide  of  hydro- 
gen differs  from  the  decomposition  of  gase- 
ous hypochlorous  acid,  or  solid  iodide  of 
nitrogen,  only  in  so  far  as  the  decomposition 
takes  place  in  a  liquid. 

A  remarkable  action  of  peroxide  of  hydro- 
gen has  attracted  much  attention,  because  it 
differs  from  ordinary  chemical  phenomena. 
This  is  the  reduction  which  certain  oxides 
suffer  by  contact  with  this  substance,  on  the 
instant  at  which  the  oxygen  separates  from 
the  water.  The  oxides  thus  easily  reduced, 
are  those  of  which  the  whole,  or  part  at 
least,  of  their  oxygen  is  retained  merely  by 
a  feeble  affinity,  such  as  the  oxides  of  silver 
and  of  gold,  and  peroxide  of  lead. 

Now,  other  oxides  which  are  very  stable 
in  composition,  effect  the  decomposition  of 
peroxide  of  hydrogen,  without  experiencing 
the  smallest  change;  but  when  oxide  of 
silver  is  employed  to  effect  the  decomposi- 
tion, all  the  oxygen  of  silver  is  carried  away 
with  that  evolved  from  the  peroxide  of  hy- 
drogen, and  as  a  result  of  the  decomposition, 
water  and  metallic  silver  remain.  When 
peroxide  of  lead  is  used  for  the  same  pur- 
pose, half  its  oxygen  escapes  as  a  gas.  Per- 
oxide of  manganese  may  in  the  same  man- 
ner be  reduced  to  the  protoxide,  and  oxygen 
set  at  liberty,  if  an  acid  is  at  the  same  time 
present,  which  will  exercise  an  affinity  for 
the  protoxide  and  convert  it  into  a  soluble 
salt.  If,  for  example,  we  add  to  peroxide 
of  hydrogen  sulphuric  acid,  and  then  per- 
oxide of  manganese  in  the  state  of  fine  pow- 
der, much  more  oxygen  is  evolved  than  the 
compound  of  oxygen  and  hydrogen  could 
yield  ;  and  if  we  examine  the  solution  which 
remains,  we  find  a  salt  of  the  protoxide  of 
manganese,  so  that  half  of  the  oxygen  has 
been  evolved  from  the  peroxide  of  that  metal. 

A  similar  phenomenon  occurs,  when  car- 
bonate of  silver  is  treated  with  several  or- 
ganic acids.  Pyruvic  acid,  for  example, 
combines  readily  with  pure  oxide  of  silver, 
and  forms  a  salt  of  sparing  solubility  in 
water.  But  when  this  acid  is  brought  in 
contact  with  carbonate  of  silver,  the  oxygen 
of  part  of  the  oxide  escapes  with  the  car- 
bonic acid,  and  metallic  silver  remains  in 
the  state  of  a  black  powder.  (Berzelius.) 

Now  no  other  explanation  of  these  phe- 
nomena cun  be  given,  than  that  a'bedy  in 
12 


the  act  of  combination  or  decomposition 
enables  another  body,  with  which  it  is  in 
contact,  to  enter  into  the  same  state.     It  is 
evident  that  the  active  state  of  the  atoms  of 
one  body  has  an  influence  upon  the  atoms 
of  a  body  in  contact  with  it;  and  if  these 
atoms  are  capable  of  the  same  change  as  the 
former,  they  likewise  undergo  that  change;, 
and  combinations  and  decompositions  are  the.  j 
consequence.     But  when  the  atoms  of  the^~ 
second   body  are   not  capable  of  such  an 
action,   any   further  disposition  to   change 
ceases  from  the  moment  at  which  the  atoms 
of  the  first  body  assume  the  state  of  rest,, 
that  is  when  the  changes  or  transformations 
of  this  body  are  quite  completed. 

This  influence  exerted  by  one  compound 
upon  the  other,  is  exactly  similar  to  that 
which  a  body  in  the  act  of  combustion  exer- 
cises upon  a  combustible  body  in  its  vicinity ; 
with  this  difference  only,  that'  the  causes 
which  determine  the  participation  and  du- 
ration of  these  conditions  are  different.  For  ""> 
the  cause,  in  the  case  of  the  combustible 
body,  is  heat,  which  is  generated  every  mo- 
ment anew ;  whilst  in  the  phenomena  of 
decomposition  and  combination,  which  we 
!  are  considering  at  present,  the  cause  is  a 
body  in  the  state  of  chemical  action,  which 
exerts  the  decomposing  influence  only  so 
long  as  this  action  continues. 

Numerous  facts  show  that  motion  alone 
exercises  a  considerable  influence  on  chemi- 
cal forces.  Thus,  the  power  of  cohesion 
does  not  act  in  many  saline  solutions,  even 
when  they  are  fully  saturated  with  salts,  if 
they  are  permitted  to  cool  while  at  rest.  In 
I  such  a  case,  the  salt  dissolved  in  a  liquid 
does  not  crystallize;  but  when  a  grain  of 
'  sand  is  thrown  into  the  solution,  or  when  it 
(  receives  the  slightest  movement,  the  whole 
liquid  becomes  suddenly  solid  while  heat 
is  evolved.  The  same  phenomenon  happens 
with  water,  for  this  liquid  may  be  cooled 
much  under  32°  F.  (0°  C.,)  if  kept  com- 
pletely undisturbed,  but  solidifies  in  a  mo- 
ment when  put  in  motion. 

The  atoms  of  a  body  must  in  fact  be  set 
in  motion  before  they  can  overcome  the  vis 
inertice  so  as  to  arrange  themselves  into  cer- 
tain forms.  A  dilute  solution  of  a  salt  of 
potash  mixed  with  tartaric  acid  yields  no 
precipitate  whilst  at  rest ;  out  if  motion  is 
communicated  to  the  solution  by  agitating 
it  briskly,  solid  crystals  of  cream  of  tartar 
are  deposited.  A  solution  of  a  salt  of  mag- 
nesia also,  which  is  not  rendered  turbid  by 
the  addition  of  phosphate  of  ammonia,  de- 
posits the  phosphate  of  magnesia  and  am- 
monia on  those  parts  of  the  vessel  touched 
with  the  rod  employed  in  stirring. 

In  the  processes  of  combination  and  de 
composition  under  consideration,  motion,  by 
overcoming  the  vis  inertice,  gives  rise  im- 
mediately to  another  arrangement  of  the 
atoms  of  a  body,  that  is,  to  the  production 
of  a  compound  which  did  not  before  exist  in 
it.  Of  course  these  atoms  must  previously 
possess  the  power  of  arranging  themselves 

H2 


90 


CKEMICAL    TRANSFORMATIONS. 


in  a  certain  order,  otherwise  both  friction  i 
and  motion  would  be  without  the  smallest 
influence. 

The  simple  permanence  in  position  of  the 
atoms  of  a  body,  is  the  reason  that  so  many 
compounds  appear  to  present  themselves,  in 
conditions,  and  with  properties,  different 
from  those  which  they  possess,  when  they 
obey  the  natural  attractions  of  their  atoms. 
Thus  sugar  and  glass,  when  melted  and 
cooled  rapidly,  are  transparent,  of  a  con- 
choidal  fracture,  and  elastic  and  flexible  to  a 
certain  degree.  But  the  former  becomes 
dull  and  opaque  on  keeping,  and  exhibits 
crystalline  faces  by  cleavage,  which  belong 
to  crystallized  sugar.  Glass  assumes  also 
the  same  condition,  when  kept  soft  by  heat 
for  a  long  period ;  it  becomes  white,  opaque, 
and  so  hard  as  to  strike  fire  with  steel. 
Now,  in  both  these  bodies,  the  compound 
molecules  evidently  have  different  positions 
in  the  two  forms.  In  the  first  form  their  at- 
traction did  not  act  in  the  direction  in  which 
their  power  of  cohesion  was  strongest.  It 
is  known  also,  that  when  sulphur  is  melted 
and  cooled  rapidly  by  throwing  it  into  cold 
water,  it  remains  transparent,  elastic,  and 
so  soft  that  it  may  be  drawn  out  into  long 
threads ;  but  that  after  a  few  hours  or  days, 
it  becomes  again  hard  and  crystalline. 

The  remarkable  fact  here  is,  that  the 
amorphous  sugar  or  sulphur  returns  again 
into  the  crystalline  condition,  without  any 
assistance  from  an  exterior  cause ;  a  fact 
which  shows  that  their  molecules  have  as- 
sumed another  position,  and  that  they  pos- 
sess, therefore,  a  certain  degree  of  mobility, 
even  in  the  condition  of  a  solid.  A  very 
rapid  transposition  or  transformation  of  this 
kind  is  seen  in  arragonite,  a  mineral  which 
possesses  exactly  the  same  composition  as 
calcareous  spar,  but  of  which  the  hardness 
and  crystalline  form  prove  that  its  molecules 
are  arranged  in  a  different  manner.  When 
a  crystal  of  arragonite  is  heated,  an  interior 
motion  of  its  molecules  is  caused  by  the  ex- 
pansion ;  the  permanence  of  their  arrange- 
ment is  destroyed ;  and  the  crystal  splinters 
with  much  violence,  and  falls  into  a  heap 
of  small  crystals  of  calcareous  spar. 

It  is  impossible  for  us  to  be  deceived  re- 
garding the  causes  of  these  changes.  They 
are  owing  to  a  disturbance  of  the  state  of 
the  equilibrium,  in  consequence  of  which 
the  particles  of  the  body  put  in  motion  obey 
other  affinities  or  their  own  natural  attrac- 
tions. 

But  if  it  is  true,  as  we  have  just  showii 
it  to  be,  that  mechanical  motion  is  sufficient 
to  cause  a  change  of  condition  in  many 
bodies,  it  cannot  be  doubted  that  a  body  in 
the  act  of  combination  or  decomposition  is 
capable  of  imparting  the  same  condition  of 
motion  or  activity  in  which  its  atoms  are  to 
certain  other  bodies  :  or  in  other  words,  to 
enable  other  bodies  with  which  it  is  in  con- 
tact to  enter  into  combinations,  or  suffer  de- 
compositions. 

The  reality  of  this  influence  has  been  al- 


ready sufficiently  proved  by  the  facts  de- 
rived from  inorganic  chemistry,  but  it  is  of 
much  more  frequent  occurrence  in  the  re- 
lations of  organic  matter,  and  causes  very 
striking  and  wonderful  phenomena. 

By  the  terms  fermentation,  putref action f 
and  eremacausis,  are  meant  tnose  changes  ia 
form  and  properties  which  compound  or- 
ganic substances  undergo  when  separated 
from  the  organism,  and  exposed  to  the  in- 
fluence of  water  and  a  certain  temperature. 
Fermentation  and  putrefaction  are  examples 
of  that  kind  of  decomposition,  which  we 
have  named  transformations :  the  elements 
of  the  bodies  capable  of  undergoing  these 
changes  arrange  themselves  into  new  com- 
binations, in  which  the  constituents  of  water 
generally  take  a  part. 

Eremacausis  (or  decay)  differs  from  fer- 
mentation and  putrefaction,  inasmuch  as  it 
cannot  take  place  without  the  access  of  air, 
the  oxygen  of  which  is  absorbed  by  the  de- 
caying bodies.  Hence  it  is  a  process  of 
slow  combustion,  in  which  heat  is  uni- 
formly evolved,  and  occasionally  even  light. 
In  the  processes  of  decomposition  termed 
fermentation  and  putrefaction,  gaseous  pro- 
ducts are  very  frequently  formed,  which  are 
either  inodorous,  or  possess  a  very  offensive 
smell. 

The  transformations  of  those  matters 
which  evolve  gaseous  products  without 
odour  are  now,  by  pretty  general  consent, 
designated  by  the  term  fermentation  ;  whilst 
to  the  spontaneous  decomposition  of  bodies 
which  emit  gases  of  a  disagreeable  smell, 
the  term  putrefaction  is  applied.  But  the 
smell  is  of  course  no  distinctive  character 
of  the  nature  of  the  decomposition,  for  both 
fermentation  and  putrefaction  are  processes 
of  decomposition  of  a  similar  kind,  the  one 
of  substances  destitute  of  nitrogen,  the  other 
of  substances  which  contain  it. 

It  has  also  been  customary  to  distinguish 
from  fermentation  and  putrefaction  a  par- 
ticular class  of  transformations,  viz.,  those 
in  which  conversions  and  transpositions  are 
effected  without  the  evolution  of  gaseous 
products.  But  the  conditions  under  which 
the  products  of  the  decomposition  present 
themselves  are  purely  accidental ;  there  is 
therefore  no  reason  for  the  distinction  just 
mentioned. 


CHAPTER  III. 

FERMENTATION  AND  PUTREFACTION. 

SEVERAL  bodies  appear  to  enter  sponta 
neously  into  the  states  of  fermentation  and 
putrefaction,  particularly  such  as  contain 
nitrogen  or  azotised  substances.  Now,  it  is 
very  remarkable,  that  very  small  quantities 
of  these  substances,  in  a  state  of  fermenta- 
tion or  putrefaction,  possess  the  power  of 
causing  unlimited  quantities  of  similar  mat- 
ters to  pass  into  the  same  state.  Thus,  a 


CHEMICAL  TRANSFORMATIONS. 


91 


Si.iall  quantity  of  the  juice  of  grapes  in  the 
act  of  fermentation,  added  to  a  large  quan- 
tity of  the  same  fluid,  which  does  not  fer- 
ment, induces  the  state  of  fermentation  in 
the  whole  mass.  So  likewise  the  most  mi- 
nute portion  of  milk,  paste,  juice  of  the 
beet-root,  flesh,  or  blood,  in  the  state  of 
putrefaction,  causes  fresh  milk,  paste,  juice 
of  the  beet-root,  flesh  or  blood,  to  pass  into 
the  same  condition  when  in  contact  with 
them. 

These  changes  evidently  differ  from  the 
class  of  common  decompositions  which  are 
effected    by    chemical    affinity;    they    are 
i  chemical  actions,  conversions,  or  decompo- 
jsitions,  excited  by  contact  with  bodies  al- 
vready  in  the  same  condition.     In  order  to 
Form  a  clear  idea  of  these  processes,  analo- 
gous and  less  complicated  phenomena  must 
previously  be  studied. 

The  compound  nature  of  the  molecules 
of  an  organic  body,  and  the  phenomena 
presented  by  them  when  in  relation  with 
other  matters,  point  out  the  true  cause  of 
these  transformations.  Evidence  is  afforded 
even  by  simple  bodies,  that  in  the  formation 
of  combinations,  the  force  with  which  the 
combining  elements  adhere  to  one  another 
is  inversely  proportional  to  the  number  of 
simple  atoms  in  the  compound  molecule. 
Thus,  protoxide  of  manganese  by  absorp- 
tion of  oxygen  is  converted  into  the  sesqui- 
oxide,  the  peroxide,  manganic  and  hyper- 
manganic  acids,  the  number  of  atoms  of 
oxygen  being  augmented  by  J,  by  1,  by  2, 
and  by  5.  But  all  the  oxygen  contained  in 
these  compounds,  beyond  that  which  belongs 
to  the  protoxide,  is  bound  to  the  manganese 
by  a  much  more  feeble  affinity;  a  red  heat 
causes  an  evolution  of  oxygen  from  the 
peroxide,  and  the  manganic  and  hyperman- 
ganic  acids  cannot  be  separated  from  their 
bases  without  undergoing  immediate  decom- 
position. 

\  There  are  many  facts  which  prove,  that 
.'he  most  simple  inorganic  compounds  are 
^  also  the  most  stable,  and  undergo  decompo- 
/  sition  with  ffre  greatest  difficulty,  whilst 
those  which  are  of  a  complex  composition 
yield  easily  to  changes  and  decompositions. 
The  cause  of  this  evidently  is,  that  in  pro- 
portion to  the  number  of  atoms  which  enter 
into  a  compound,  the  directions  in  which 
their  attractions  act  will  be  more  numerous. 
Whatever  ideas  we  may  entertain  regard- 
ing the  infinite  divisibility  of  matter  in 
general,  the  existence  of  chemical  propor- 
tions removes  every  doubt  respecting  the  pre- 
sence of  certain  limited  groups  or  masses  of 
matter  which  we  have  not  the  power  of  divid- 
ing. The  particles  of  matter  called  equiva- 
lents in  chemistry  are  not  infinitely  small,  for 
they  possess  a  weight,  and  are  capable  of 
arranging  themselves  in  the  most  various 
ways,  and  of  thus  forming  innumerable 
compound  atoms.  The  properties  of  these 
compound  atoms  differ  in  organic  nature, 
not  only  according  to  the  form,  but  also  in 
many  instances  according  to  the  direction 


and  place,  which  the  simple  atoms  take  iu 
the  compound  molecules. 

When  we  compare  the  composition  of 
organic  compounds  with  inorganic,  we  are 
quite  amazed  at  the  existence  of  combina- 
tions, in  one  single  molecule  of  which, 
ninety  or.  several  hundred  atoms  or  equiva 
lents  are  united.  Thus,  the  compound  atom 
of  an  organic  acid  of  very  simple  composi- 
tion, acetic  acid  for  example,  contains  twelve 
equivalents  of  simple  elements ;  one  atom 
of  kinovic  acid  contains  33,  1  of  sugar  36, 
1  of  amygdalin  90,  and  1  of  stearic  acid  138 
equivalents.  The  component  parts  of  ani- 
mal bodies  are  infinitely  more  complex  even 
than  these. 

Inorganic  compounds  differ  from  organic  \ 
in  as  great  a  degree  in  their  other  characters  \ 
as  in  their  simplicity  of  constitution.  Thus, 
the  decomposition  of  a  compound  atom  of 
sulphate  of  potash  is  aided  by  numerous 
causes,  such  as  the  power  of  cohesion,  or 
the  capability  of  its  constituents  to  form 
solid,  insoluble,  or  at  certain  temperatures 
volatile  compounds  with  the  body  brought 
into  contact  with  it,  and  nevertheless  a.  vast 
number  of  other  substances  produce  in  it 
not  the  slightest  change.  Now,  in  the- de- 
composition of  a  complex  organic  atom, 
there  is  nothing  similar  to  this. 

The  empirical  formula  of  sulphate  of 
potash  is  SKO4.  It  contains  only  1  eq.  of 
sulphur,  and  1  eq.  of  potassium.  We  may 
suppose  the  oxygen  to  be  differently  distri- 
buted in  the  compound,  and  by  a  decompo- 
sition we  may  remove  a  part  or  all  of  it,  or 
replace  one  of  the  constituents  of  the  com- 
pound by  another  substance.  But  we  can- 
not produce  a  different  arrangement  of  the 
atoms,  because  they  are  already  disposed  in 
the  simplest  form  in  which  it  is  possible  for 
them  to  combine.  Now,  let  us  compare  the 
composition  of  sugar  of  grapes  with  the 
above:  here  12  eq.  of  carbon,  12  eq.  of 
hydrogen,  and  12  eq.  of  oxygen,  are  united 
together,  and  we  know  that  they  are  capa- 
ble of  combining  with  each  other  in  the 
most  various  ways.  From  the  formula  of 
sugar  we  might  consider  it  either  as  a  hy- 
drate of  carbon,  wood,  starch,  or  sugar  of 
milk,  or  farther,  as  a  compound  of  ether 
with  alchohol  or  of  formic  acid  with  sachul- 
min.*  Indeed  we  may  calculate  almost  all 
the  known  organic  compounds  destitute  of 
nitrogen  from  sugar,  by  simply  adding  the 
|  elements  of  water,  or  by  replacing  any  one 
of  its  elementary  constituents  by  a  different 
substance.  The  elements  necessary  to  form 
these  compounds  are  therefore  contained  in 
the  sugar,  and  they  must  also  possess  the 
power  of  forming  numerous  combinations 
amongst  themselves  by  their  mutual  attrac 
tions. 

Now,  when  we  examine  what  changes 
sugar  undergoes  when  brought  into  contact 
with  other  bodies  which  exercise  a  marked 


*  The  black  precipitate  obtained  by  the  action 
of  hydrochloric  acid  on  sugar. 


AGRICULTURAL   CHEMISTRY. 


influence  upon  it,  we  find,  that  these  changes  !  combined,  to  undergo  the  same  decomposi- 

are  not  confined  to  any  narrow  limits,  like 

those  of  inorganic  bodies,   but  are  in  fact 

unlimited. 
The  elements  of  sugar  yield  to  every  at- 

<.raction,  and  to  each  in  a  peculiar  manner. 

In  inorganic  compounds,  an  acid  acts  upon 

a  particular  constituent  of  the  body,  which 

it  decomposes,  by  virtue  of  its  affinity  for 

that  constituent,  and  never  resigns  its  proper 

chemical  character,  in  whatever  form  it  may 

be  applied.  But  when  it  acts  upon  sugar, 
I  and  induces  great  changes  in  that  compound, 
1  it  does  this  not  by  any  superior  affinity  for 
|  a  base  existing  in  the  sugar,  but  by  disturb- 
Ung  the  equilibrium  in  the  mutual  attraction 
iof  the  elements  of  the  sugar  amongst  them- 
jselves.  Muriatic  and  sulphuric  acids,  which 

differ  so  much  from  one  another  both  in 

characters  and  composition,  act  in  the  same 

manner  upon  sugar.     But  the  action  of  both 

varies  according  to  the  state  in  which  they 

are ;  thus  they  act  in  one  way  when  dilute, 

in  another  when  concentrated,  and  even  dif- 
ferences in  their 
their  action 


in 


ir  temperature  cause  a  change 
.  Thus  sulphuric  acid  of  a 
moderate  degree  of  concentration  converts 
sugar  into  a  black  carbonaceous  matter, 
forming  at  the  same  time  acetic  and  formic 
acids.  But  when  the  acid  is  more  diluted, 
the  sugar  is  converted  into  two  brown  sub- 
stances, both  of  them  containing  carbon  and 
the  elements  of  water.  Again,  when  sugar 
is  subjected  to  the  action  of  alkalies,  a  whole 
series  of  different  new  products  are  obtained ; 
wnile  oxidizing  agents,  such  as  nitric  acid, 
produce  from  it  carbonic  acid,  acetic  acid, 
oxalic  acid,  formic  acid,  and  many  other 
products  which  have  not  yet  been  examined. 

If  from  the  facts  here  stated  we  estimate 
the  power  with  which  the  elements  of  sugar 
are  united  together,  and  judge  of  the  force 
of  their  attraction  by  the  resistance  which 
they  offer  to  the  action  of  bodies  brought 
into  contact  with  them,  we  must  regard  the 
atom  of  sugar  as  belonging  to  that  class  of 
compound  atoms,  which  exist  only  by  the 
vis  inerticK  of  their  elements.  Its  elements 
seem  merely  to  retain  passively  the  position 
and  condition  in  which  they  had  been 
placed,  for  we  do  not  observe  that  they  re- 
sist a  change  of  this  condition  by  their  own 
mutual  attraction,  as  is  the  case  with  sul- 
phate of  potash. 

Now  it  is  only  such  combinations  as 
sugar,  combinations  therefore  which  possess 
a  very  complex  molecule,  which  are  capa- 
ble of  undergoing  the  decompositions  named 
fermentation  and  putrefaction. 

We  have  seen  that  metals  acquire  a  power 
vhich  they  do  not  of  themselves  possess, 
nauiely,  that  of  decomposing  water  and 
nitric  acid,  by  simple  contact  with  other 
metals  in  the  act  of  chemical  combination. 
We  have  also  seen,  that  peroxide  of  hydro- 
gen and  the  persulphuret  of  the  same  ele- 
ment, in  the  act  of  decomposition,  cause 
other  compounds  of  a  similar  kind,  but  of 
which  the  elements  are  much  more  strongly 


tion,  although  they  exert  no  chemical  af- 
finity or  attraction  for  them  or  their  consti- 
tuents. The  cause  which  produces  these 
phenomena  will  be  also  recognised,  by  at- 
tentive observation,  in  those  matters  which 
excite  fermentation  or  putrefaction.  All 
bodies  in  the  act  of  combination  or  decom- 
position have  the  property  of  inducing  those 
processes ;  or,  in  other  words,  of  causing  a 
disturbance  of  the  statical  equilibrium  in 
the  attractions  of  the  elements  of  complex 
organic  molecules,  in  consequence  of  which 
those  elements  group  themselves  anew,  ac- 
cording to  their  special  affinities. 

The  proofs  of  the  existence  of  this  cause 
of  action  can  be  easily  produced ;  they  are 
found  in  the  characters  of  the  bodies  which 
effect  fermentation  and  putrefaction,  and  in 
the  regularity  with  which  the  distribution 
of  the  elements  takes  place  in  the  subse- 
quent transformations.  This  regularity  de- 
pends exclusively  on  the  unequal  affinity 
which  they  possess  for  each  other  in  an 
isolated  condition.  The  action  of  water  on 
wood,  charcoal,  and  cyanogen,  the  simplest 
of  the  compounds  of  nitrogen,  suffices  to  il- 
lustrate the  whole  of  the  transformations  of 
organic  bodies;  of  those  in  which  nitrogen 
is  a  constituent,  and  of  those  in  which  it  is 
absent. 


CHAPTER  IV. 

ON  THE  TRANSFORMATION  OF  BODIES  WHICH 
DO  NOT  CONTAIN  NITROGEN  AS  A  CONSTI- 
TUENT, AND  OF  THOSE  IN  WHICH  IT  IS 
PRESENT. 

WHEN  oxygen  and  hydrogen  combined 
in  equal  equivalents,  as  in  steam,  are  con- 
ducted over  charcoal,  heated  to  the  tempe- 
rature at  which  it  possesses  the  power  to 
enter  into  combination  with  one  of  these 
elements,  a  decomposition  of  steam  ensues. 
An  oxide  of  carbon  (either  carbonic  oxide 
or  carbonic  acid)  is  under  all  circumstances 
formed,  while  the  hydrogen  of  the  water  is 
liberated,  or,  if  the  temperature  be  sufficient, 
unites  with  the  carbon,  forming  carburetted 
hydrogen.  Accordingly,  the  carbon  is  shared 
between  the  elements  of  the  water,  the  oxy- 
gen and  hydrogen.  Now  a  participation  of 
this  kind,  but  even  more  complete,  is  ob- 
served in  every  transformation,  whatever 
be  the  nature  of  the  causes  by  which  it  is 
effected. 

Acetic  and  meconic*  acids  suffer  a  tine 
transformation  under  the  influence  of  heat, 
that  is,  their  component  elements  are  dis- 
united, and  form  new  compounds  without 
any  of  them  being  singly  disengaged.  Acetic 
acid  is  converted  into  acetone  and  carbonic 


*  An  acid  existing  in  opium,  and  named  from 
the  Greek  for  poppy. 


CHEMICAL    TRANSFORMATIONS, 


acid  (04  H3  O3=C3  H3  O  +  CO2,)  and 
meconic  acid  into  carbonic  acid  and  kome- 
nic  acid;  whilst  by  the  influence  of  a  higher 
temperature,,  the  latter  is  further  decomposed 
into  pyromeconic  acid  and  carbonic  acid. 

Now  in  these  cases  the  carbon  of  the  bo- 
dies decomposed  is  shared  between  the  oxy- 
gen and  the  hydrogen ;  part  of  it  unites  with 
the  oxygen  and  forms  carbonic  acid,  whilst 
the  other  portion  enters  into  combination 
with  the  hydrogen,  and  an  oxide  of  a  carbo- 
hydrogen  is  formed,  in  which  all  the  hy- 
drogen is  contained. 

In  a  similar  manner,  when  alcohol  is 
exposed  to  a  gentle  red  heat,  its  carbon  is 
shared  between  the  elements  of  the  water — 
an  oxide  of  a  carbo-hydrogen  which  con- 
tains all  the  oxygen,  and  some  gaseous  com- 
pounds of  carbon  and  hydrogen  being  pro- 
duced. 

It  is  evident  that  during  transformations 
caused  by  heat,  no  foreign  affinities  can  be 
in  play,  so  that  the  new  compounds  must 
result  merely  from  the  elements  arranging 
themselves.,  according  to  the  degree  of  their 
mutual  affinities,  into  new  combinations 
which  are  constant  and  unchangeable  in 
*he  conditions  under  which  they  were  origi- 
nally formed,  but  undergo  changes  when 
these  conditions  become  different.  If  we 
compare  the  products  of  two  bodies,  similar 
in  composition  but  different  in  properties, 
which  are  subjected  to  transformations  by 
two  different  causes,  we  find  that  the  man- 
ner in  which  the  atoms  are  transposed,  is 
absolutely  the  same  in  both. 

In  the  transformation  of  wood  in  marshy 
soils,  by  what  we  call  putrefaction,  its  car- 
bon is  shared  between  the  oxygen  and  hy- 
drogen of  its  own  substance,  and  of  the 
water — carburetted  hydrogen  is  consequently 
evolved,  as  well  as  carbonic  acid,  both  of 
which  compounds  have  an  analogous  com- 
position (CH2,  CO2.) 

Thus  also  in  that  transformation  of  sugar, 
which  is  called  fermentation,  its  elements 
are  divided  into  two  portions ;  the  one,  car- 
bonic acid,  which  contains  f  of  the  oxygen 
of  sugar ;  and  the  other,  alcohol,  which  con- 
tains all  its  hydrogen. 

In  the  transformation  of  acetic  acid  pro- 
duced by  a  red  heat,  carbonic  acid,  which 
contains  2-3  of  the  oxygen  of  the  acetic  acid 
is  formed,  and  acetone,  which  contains  al 
its  hydrogen. 

It  is  evident  from  these  facts,  that  the  ele- 
ments of  a  complex  compound  are  left  to 
their  special  attractions  whenever  their  equi- 
librium is  disturbed,  from  whatever  cause 
this  disturbance  may  proceed.  It  appears 
also,  that  the  subsequent  distribution  of  the 
elements,  so  as  to  form  new  combinations 
always  takes  place  in  the  same  way,  with 
this  difference  only,  that  the  nature  of  the 
products  formed  is  dependent  upon  the  num 
oer  of  atoms  of  the  elements  which  ente 
into  action  ;  or,  in  other  words,  that  the  pro- 
ducts differ  ad  infinitum,  according  to  the 
composition  of  the  original  substance 


N    THE    TRANSFORMATION    OF    BODIES    COW- 
TAINING    NITROGEN. 

When   those    substances  are    examined 

which  are  most  prone  to  fermentation  and 

utrefaction,  it  is  found  that  they  are  all, 

without  exception,    bodies  which    contain 

itrogen.     In  many  of  these  compounds,  a 

ransposition  of  their  elements  occurs  spon- 

aneously  as  soon  as  they  cease  to  form  part 

f  a  living  organism;  that  is,  when  they  are 

Irawn   out  of  the  sphere   of  attraction  in 

which  alone  they  are  able  to  exist. 

There  are,  indeed,  bodies  destitute  of  ni- 
rogen,  which  possess  a  certain  degree  of 
liability  only  when  in  combination,  but 
which  are  unknown  in  an  isolated  condition, 
jecause  their  elements,  freed  from  the  power 
)y  which  they  were  held  together,  arrange 
hemselves  according  to  their  own  natural 
attractions.  Hypermanganic,  maganic,  and 
lyposulphurous  acids,  belong  to  this  class 
of  substances,  which  however  are  rare. 

The  case  is  very  different  with  azotised 
)odies.  It  would  appear  that  there  is  some 
Deculiarity  in  the  nature  of  nitrogen,  which 
*ives  its  compounds  the  power  to  decom- 
pose spontaneously  with  so  much  facility. 
Mow,  nitrogen  is  known  to  be  the  most  in- 
different of  all  the  elements;  it  evinces  no 
particular  attraction  to  any  one  of  the  simple 
bodies;  and  this  character  it  preserves  in  all 
ts  combinations,  a  character  which  explains 
the  cause  of  its  easy  separation  from  the 
matters  with  which  it  is  united. 

It  is  only  when  the  quantity  of  nitrogen 
exceeds  a  certain  limit,  that  azotised  com- 
pounds have  some  degree  of  permanence,  as 
is  the  case  with  melamin,  ammelin,  &c. 
Their  liability  to  change  is  also  diminished, 
when  the  quantity  of  nitrogen  is  very  small 
in  proportion  to  that  of  the  other  elements 
with  which  it  is  united,  so  that  their  mutual 
attractions  preponderate. 

This  easy  transposition  of  atoms  is  best 
seen  in  the  fulminating  silvers,  in  fulmi- 
nating mercury,  in  the  iodide  or  chloride  of 
nitrogen,  and  in  all  fulminating  compounds. 
All  other  azotised  substances  acquire  the 
same  power  of  decomposition,  when  the 
elements  of  water  are  brought  into  play ; 
and  indeed,  the  greater  part  of  them  are  not 
capable  of  transformation,  while  this  neces- 
sary condition  to  the  transposition  of  their 
atoms  is  absent.  Even  the  compounds  of  ni- 
trogen, which  are  most  liable  to  change, 
such  as  those  which  are  found  in  animal 
bodies,  do  not  enter  into  a  slate  of  putrefac- 
faclion  when  dry. 

The  resull  of  the  known  transformations 
of  azotised  substances  proves  that  the  water 
does  not  merely  act  as  a  medium  in  which 
motion  is  permitted  to  the  elements  in  the 
act  of  transposition,  but  thai  its  influence 
depends  on  chemical  affinity.  When  the 
decomposition  of  such  substances  is  effected 
with  the  assistance  of  water,  their  nitrogen 
is  invariably  liberated  in  the  form  of  ammo- 
|  nia.  This  is  a  fixed  rule  without  any  excep* 


94 


AGRICULTURAL   CHEMISTRY. 


tions,  whatever  may  be  the  cause  which 
produces  the  decompositions.  All  organic 
compounds  containing  nitrogen,  evolve  the 
whole  of  that  element  in  the  form  of  ammo- 
nia when  acted  on  by  alkalies.  Acids,  and 
increase  of  temperature,  produce  the  same 
effect.  It  is  only  when  there  is  a  defi- 
ciency of  water  or  its  elements,  that  cyno- 
gen  or  other  azotised  compounds  are  pro- 
duced. 

From  these  facts  it  may  be  concluded, 
that  ammonia  is  the  most  stable  compound 
of  nitrogen ;  and  that  hydrogen  and  nitro- 
gen possess  a  degree  of  affinity  for  each 
other  surpassing  the  attraction  of  the  latter 
body  for  any  other  element. 

Already  in  considering  the  transforma- 
tions of  substances  destitute  of  nitrogen,  we 
have  recognised  the  great  affinity  of  carbon 
for  oxygen  as  a  powerful  cause  for  effecting 
the  disunion  of  the  elements  of  a  complex 
organic  atom  in  a  definite  manner.  But  car- 
bon is  also  invariably  contained  in  azotised 
organic  compounds,  while  the  great  affinity 
of  nitrogen  for  hydrogen  furnishes  a  new 
and  powerful  cause,  facilitating  the  transpo- 
sition of  their  component  parts.  Thus,  in 
the  bodies  which  do  not  contain  nitrogen  we 
have  one  element,  and  in  those  in  which 
that  substance  is  present,  two  elements, 
which  mutually  share  the  elements  of  water. 
Hence  there  are  two  opposite  affinities  at 
play,  which  mutually  strengthen  each  other's 
actions. 

Now  we  know,  that  the  most  powerful 
attractions  may  be  overcome  by  the  influ- 
ence of  two  affinities.  Thus,  a  decomposi- 
tion of  alumina  may  be  effected  with  the 
greatest  facility,  when  the  affinity  of  char- 
coal for  oxygen,  and  of  chlorine  for  alumi- 
nium, are  both  put  in  action,  although  nei- 
ther of  these  alone  has  any  influence  upon 
it.  There  is  in  the  nature  and  constitution 
of  the  compounds  of  nitrogen  a  kind  of  ten- 
sion of  their  component  parts,  and  a  strong 
disposition  to  yield  to  transformations,  which 
effect  spontaneously  the  transposition  of 
their  atoms  on  the  instant  that  water  or 
its  elements  are  brought  in  contact  with 
them. 

The  characters  of  the  hydrated  cyanic 
acid,  one  of  the  simplest  of  all  the  com- 
pounds of  nitrogen,  are  perhaps  the  best 
adapted  to  convey  a  distinct  idea  of  the 
manner  in  which  the  atoms  are  disposed  of 
in  transformations.  This  acid  contains  ni- 
trogen, hydrogen,  and  oxygen,  in  such  pro- 
portions, that  the  addition  of  a  certain  quan- 
tity of  the  elements  of  water  is  exactly  suffi- 
cient to  cause  the  oxygen  contained  in  the 
water  and  acid  to  unite  with  the  carbon  and 
form  carbonic  acid,  and  the  hydrogen  of  the 
water  to  combine  with  the  nitrogen  and 
form  ammonia.  The  most  favourable  con- 
ditions for  a  complete  transformation  are, 
therefore,  associated  in  these  bodies,  and  it 
is  well  known,  that  the  disunion  takes  place 
on  the  instant  in  which  the  cyanic  acid  and 
water  are  brought  into  contact,  the  mixture 


being  converted  into  carbonic  acid  and  am 
monia,  with  brisk  effervescence. 

This  decomposition  may  be  considered  as 
the  type  of  the  transformations  of  all  azo- 
tised compounds;  it  is  putrefaction  in  its 
simplest  and  most  perfect  form,  because  the 
new  products,  the  carbonic  acid  and  ammo- 
nia are  incapable  of  further  transformations. 

Putrefaction  assumes  a  totally  different 
and  much  more  complicated  form,  when  the 
products,  which  are  first  formed  undergo  a 
further  change.  In  these  cases  the  proress 
consists  of  several  stages,  of  which  it  is  im- 
possible to  determine  when  one  ceases  and 
the  other  begins. 

The  transformations  of  cyanogen,  a  bodv 
composed  of  carbon  and  nitrogen,  and  the 
simplest  of  all  the  compounds  of  nitrogen, 
will  convey  a  clear  idea  of  the  great  variety 
of  products  which  are  produced  in  such  a 
case  :  it  is  the  only  example  of  the  putrefac- 
tion of  an  azotised  body  which  has  been  at 
all  accurately  studied. 

A  solution  of  cyanogen  in  water  becomes 
turbid  after  a  short  time,  and  deposits  a 
black,  or  brownish  black  matter,  which  is  a 
combination  of  ammonia  with  another  body, 
produced  by  the  simple  union  of  cyanogen 
with  water.  This  substance  is  insoluble  in 
water,  and  is  thus  enabled  to  resist  further 
change. 

A  second  transformation  is  effected  Vy  the 
cyanogen  being  snared  between  the  elements 
of  the  water,  in  consequence  of  which 
cyanic  acid  is  formed  by  a  certain  quantity 
of  the  cyanogen  combining  with  the  oxygen 
of  the  water,  while  hydrocyanic  acid  is  also 
formed  by  another  portion  of  the  cyanogen 
uniting  with  the  hydrogen  which  was  libe- 
rated. 

Cyanogen  experiences  a  third  transforma- 
tion, by  which  a  complete  disunion  of  its 
elements  takes  place,  these  being  divided  be- 
tween the  constituents  of  the  water.  Oxa- 
lic acid  is  the  one  product  of  this  disunion, 
and  ammonia  the  other. 

Cyanic  acid,  the  formation  of  which  has 
been  mentioned  above,  cannot  exist  in  con- 
tact with  water,  being  decomposed  immedi- 
ately into  carbonic  acid  and  ammonia.  The 
cyanic  acid,  however,  newly  formed  in  the 
decomposition  of  cyanogen,  escapes  this  de- 
composition by  entering  into  combination 
with  the  free  ammonia,  by  which  urea  is 
produced. 

The  hydrocyanic  acid  is  also  decomposed 
into  a  brown  matter  which  contains  hydro 
gen  and  cyanogen,  the  latter  in  greater  pro 
portion  than  it  does  in  the  gaseous  state. 
Oxalic  acid,  urea,  and  carbonic  acid,  are  also 
formed  by  its  decomposition,  and  formic  acid 
and  ammonia  are  produced  by  the  decompo- 
sition of  its  radical. 

Thus,  a  substance  into   the  composition 

of  which  only  two  elements   (carbon  and 

I  nitrogen)  enter,  yields  ei^ht  totally  different 

:  products.     Several  of   these   products   a»-e 

;  formed  by  the  transformation  of  the  original 

body,  its  elements  being  shared  between  the 


CHEMICAL   TRANSFORMATIONS. 


95 


constituents  of  water ;  others  are  produced 
in  consequence  of  a  further  disunion  of 
those  first  formed.  The  urea  and  carbonate 
of  ammonia  are  generated  by  the  combina- 
tion of  two  of  the  products,  and  in  their  for- 
mation the  whole  of  the  elements  have  as- 
sisted. 

These  examples  show,  that  the  results  of 
decomposition  by  fermentation  or  putrefac- 
tion comprehend  very  different  phenomena. 
The  first  kind  of  transformation  is,  the 
transposition  of  the  elements  of  one  complex 
compound,  by  which  new  compounds  are 
produced  \yJlfLQr  without  the  assistance  of 
the  elements  of  water.  In  the  products 
newly  formed  in  this  manner,  either  the 
same  proportions  of  those  component  parts 
which  were  contained  in  the  matter  before 
transformation,  are  found,  or  with  them,  an 
excess,  consisting  of  the  constituents  of  wa- 
ter which  had  assisted  in  promoting  the  dis- 
union of  the  elements. 

The  second  kind  of  transformation  con- 
sists of  the  transpositions  of  the  atoms  of 
two  or  more  complex  compounds,  by  which 
the  elements  of  both  arrange  themselves 
mutually  into  new  products,  with  or  with- 
out the  co-operation  of  the  elements  of  wa- 
ter. In  this  kind  of  transformations,  the 
new  products  contain  the  sum  of  the  con- 
stituents of  all  the  compounds  which  had 
taken  a  part  in  the  decomposition. 

The  first  of  these  two  modes  of  decom- 
position is  that  designated  fermentation,  the 
second  putrefaction  ;  and  when  these  terms 
are  used  in  the  following  pages,  it  will 
always  be  to  distinguish  the  two  processes 
above  described,  which  are  so  different  in 
their  results. 


CHAPTER  V. 

FERMENTATION   OF   SUGAR. 

THE  peculiar  decomposition  which  sugar 
suffers  may  be  viewed  as  a  type  of  all  the 
transformations  designated  fermentation.* 

Thenard  obtained  from  100  grammes  of 
cane-sugar  0.5262  of  absolute  alcohol.  100 
parts  of  sugar  from  the  cane  yield,  there- 


:  I'/*  When  yeast  is 
water,  and  I  cubic  c 
Produced  into  agrad 


made  into  a  thin  paste  with 
cubic  centimetre  of  this  mixture  in- 
.  graduated  glass  receiver  filled  with 
mercury,  in  which  are  already  19  grammes  of  a 
solution  of  cane  sugar,  containing  1  gramme  of 
pure  solid  sugar ;  it  is  found  after  the  mixture  has 
been  exposed  for  24  hours  to  a  temperature  of 
from  20  to  25  C.  (68—77  F.,)  that  a  volume  of 
carbonic  acid  has  been  formed,  which,  at  0*  C. 
(32°  F.)  and  an  atmospheric  pressure  indicated  by 
0.76  metre  Bar.  would  be  from  245  to  250  cubic 
centimetres.  But  to  this  quantity  we  must  add  11 
cubic  centimetres  of  carbonic  acid,  with  which 
the  11  grammes  of  liquid  would  be  saturated,  so 
that  in  all  255 — 259  cubic  centimetres  of  carbonic 
acid  are  obtained.  This  volume  of  carbonic  acid 
corresponds  to  from  0.503  to  0.5127  grammes  by 
weight. 


fore,  103.89  parts  of  carbonic  acid  and  alco- 
hol. The  entire  carbon  in  these  products  is 
equal  to  42  parts,  which  is  exactly  the  quan- 
tity originally  contained  in  the  sugar. 

The  analysis  of  sugar  from  the  cane, 
proves  that  it  contains  the  elements  of  car- 
oonic  acid  and  alcohol,  minus  1  atom  of 
water.  The  alcohol  and  carbonic  acid  pro- 
duced by  the  fermentation  of  a  certain  quan-\ 
tity  of  sugar,  contain  together  one  equivalent 
of  oxygen  and  one  equivalent  of  hydrogen, 
the  elements,  therefore,  of  one  equivalent 
of  water,  more  than  the  sugar  contained. 
The  excess  of  weight  in  the  products  is 
thus  explained  most  satisfactorily  ;  it  is  ow- 
ing, namely,  to  the  elements  of  water  hav- 
ing taken  part  in  the  metamorphosis  of  the 
sugar. 

It  is  known  that  1  atom  of  sugar  contains 
12  equivalents  of  carbon,  both  from  the 
proportions  in  which  it  unites  with  bases, 
and  from  the  composition  of  saccharic  acid 
the  product  of  its  oxidation.  Now  none  of 
these  atoms  of  carbon  are  contained  in  the 
sugar  as  carbonic  acid,  because  the  whole 
quantity  is  obtained  as  oxalic  acid,  when 
sugfir  is  treated  with  hypermanganate  of 
potash  (Gregory ;)  and  as  oxalic  acid  is  a 
lower  degree  of  the  oxidation  of  carbon  than 
carbonic  acid,  it  is  impossible  to  conceive 
that  the  lower  degree  should  be  produced 
from  the  higher,  by  means  of  one  of  the 
most  powerful  agents  of  oxidation  which 
we  possess. 

It  can  be  also  proved,  that  the  hydrogen 
of  the  sugar  does  not  exist  in  it  in  the  form 
of  alcohol,  for  it  is  converted  into  water 
and  a  kind  of  carbonaceous  matter,  when 
treated  with  acids,  particularly  .with  such  as 
contain  no  oxygen ;  and  th'is  manner  of  de- 
composition is  never  suffered  by  a  com- 
pound of  alcohol. 

Sugar  contains,  therefore,  neither  alcohoi 
nor  carbonic  acid,  so  that  these  bodies  must 
be  produced  by  a  different  arrangement  of  its 
atoms,  and  by  their  union  with  the  elements 
of  water. 

In  this  metamorphosis  of  sugar,  the  ele 
ments  of  the  yeast,  by  contact  with  which 
its  fermentation  was  effected,  take  no  appre- 
ciable part  in  the  transposition  of  the  ele- 
ments of  the  sugar;  for  in  the  products 
resulting  from  the  action,  we  find  no  com- 
ponent part  of  this  substance. 

We  may  now  study  the  fermentation  of 
a  vegetable  juice,  which  contains  not  only 
saccharine  matter,  but  also  such  substances 
as  albumen  and  gluten.  The  juices  of 
parsneps,  beet-roots,  and  onions,  are  well 
adapted  for  this  purpose.  When  such  a 
juice  is  mixed  with  yeast  at  common 
temperatures,  it  ferments  like  a  solution  of 
sugar.  Carbonic  acid  gas  escapes  from  it 
with  effervescence,  and  in  the  liquid,  alcohol 
is  found  in  quantity  exactly  corresponding 
to  that  of  the  sugar  originally  contained  in 
the  juice.  But  such  a  juice  undergoes  spon- 
taneous decomposition  at  a  temperature  of 
from  950  to  1040  (350—40°  CO  Gases 


AGRICULTURAL    CHEMISTRY. 


possessing  an  offensive  smell  are  evolved  in 
considerable  quantity.,  and  when  the  liquor 
is  examined  after  the  decomposition  is  com- 
pleted,, no  alcohol  can  be  detected.  The 
sugar  has  also  disappeared,  and  with  it  all 
the  azotised  compounds  which  existed  in  the 
juice  previously  to  its  fermentation.  Both 
were  decomposed  at  the  same  time ;  the  nitro- 
gen of  the  azotised  compounds  remains  in  the 
liquid  as  ammoina,  and,  in  addition  to  it, 
there  are  three  new  products,  formed  from 
the  component  parts  of  the  juice.  One  of 
these  is  lactic  acid,  the  slightly  volatile  com- 
pound found  in  the  animal  organism ;  the 
other  is  the  crystalline  body  which  forms 
the  principal  constituent  of  manna ;  and  the 
third  is  a  mass  resembling  gum-arabic,  which 
forms  a  thick  viscous  solution  with  water. 
These  three  products  weigh  more  than  the 
sugar  contained  in  the  juice,  even  without 
calculating  the  weight  of  the  gaseous  pro- 
ducts. Hence  they  are  not  produced  from 
the  elements  of  the  sugar  alone.  None  of 
these  three  substances  could  be  detected  in 
the  juice  before  fermentation.  They  must, 
therefore,  have  been  formed  by  the  inter- 
change of  the  elements  of  the  sugar  with 
those  of  the  foreign  substances  also  present. 
It  is  this  mixed  transformation  of  two  or 
--inore  compounds  which  receives  the  special 
lame  of  putrefaction. 

YEAST    OR    FERMENT. 

When  attention  is  directed  to  the  condi- 
tion of  those  substances  which  possess  the 
power  of  inducing  fermentation  and  putre- 
faction in  other  bodies,  evidences  are  found 
m  their  general  characters,  and  in  the  man- 
ner in  which  they  combine,  that  they  all  are 
bodies,  the  atoms  of  which  are  in  the  act  of 
transposition. 

The  characters  of  the  remarkable  matter 
which  is  deposited  in  an  insoluble  state 
during  the  fermentation  of  beer,  wine,  and 
vegetable  juices,  may  first  be  studied. 

This  substance,  which  has  been  called 
yeast  or  ferment,  from  the  power  which  it 
possesses  of  causing  fermentation  in  sugar, 
or  saccharine  vegetable  juices,  possesses  all 
the  characters  of  a  compound  of  nitrogen  in 
the  state  of  putrefaction  and  eremacausis. 

Like  wood  in  the  state  of  eremacausis, 
yeast  converts  the  oxygen  of  the  surrounding 
air  into  carbonic  acid,  but  it  also  evolves  this 
gas  from  its  own  mass,  like  bodies  in  the 
state  of  putrefaction.  (Colin.)  When  kept 
underwater,  it  emits  carbonic  acid,  accompa- 
nied by  gases  of  an  offensive  smell,  (The- 
nard,)  and  is  at  last  converted  into  a  sub- 
stance resembling  old  cheese.  (Proust.) 
But  when  its  own  putrefaction  is  completed, 
it  has  no  longer  the  power  of  inducing  fer- 
mentation in  other  bodies.  The  presence 
of  water  is  quite  necessary  for  sustaining 
the  properties  of  ferment,  for  by  simple  pres- 
sure its  power  to  excite  fermentation  is 
much  diminished,  and  is  completely  de- 
stroved  by  drying.  Its  action  is  arrested  also 


by  the  temperature  of  boiling  water,  by  al- 
cohol, common  salt,  an  excess  of  sugar, 
oxide  of  mercury,  corrosive  sublimate,  pyro- 
ligneous  acid,  sulphurous  acid,  nitrate  of 
silver,  volatile  oils,  and  in  short  by  ah1  anti- 
i  septic  substances. 

The  insoluble  part  of  the  substance  called 
ferment  does  not  cause  fermentation.  For 
when  the  yeast  from  wine  or  beer  is  care- 
fully washed  with  water,  care  being  taken 
that  it  is  always  covered  with  this  fluid,  the 
residue  does  not  produce  fermentation. 

The  soluble  part  of  ferment  likewise  does 
not  excite  fermentation.  An  aqueous  infu- 
sion of  yeast  may  be  mixed  with  a  solution 
of  sugar,  and  preserved  in  vessels  from  which 
the  air  is  excluded,  without  either  experi- 
encing the  slightest  change.  What  then,  we 
may  ask,  is  the  matter  in  ferment  which  ex- 
cites fermentation,  if  neither  the  solu  ble  nor 
insoluble  parts  possess  the  power?  This 
question  has  been  answered  by  Colin  in  the 
most  satisfactory  manner.  He  has  shown 
that  in  reality  it  is  the  soluble  part.  But 
before  it  obtains  this  power,  the  decanted 
infusion  must  be  allowed  to  cool  in  contact 
with  the  air,  and  to  remain  some  time  ex- 
j  posed  to  its  action.  When  introduced  into 
a  solution  of  sugar  in  this  state,  it  produces 
a  brisk  fermentation;  but  without  previous 
exposure  to  the  air,  it  manifests  no  such 
property. 

The  infusion  absorbs  oxygen  during-  its 
exposure  to  the  air,  and  carbonic  acid  may 
be  found  in  it  after  a  short  time. 

Yeast  produces  fermentation  in  conse- 
quence of  the  progressive  decomposition 
which  it  suffers  from  the  action  of  air  and 
water. 

Now  when  yeast  is  made  to  act  on  sugar, 
it  is  found,  that  after  the  transformation  of 
the  latter  substance  into  carbonic  acid  and 
alcohol  is  completed,  part  of  the  yeast  itself 
has  disappeared. 

From  20  parts  of  fresh  yeast  from  beer, 
and  100  parts  of  sugar,  Thenard  obtained, 
after  the  fermentation  was  completed,  13'7 
parts  of  an  insoluble  residue,  which  dimi- 
nished to  10  parts  when  employed  in  the 
same  way  with  a  fresh  portion  of  sugar. 
These  ten  parts  were  white,  possessed  of  the 
properties  of  woody  fibre,  and  had  no  farther 
action  on  sugar. 

It  is  evident,  therefore,  that  during  the  fer- 
mentation of  sugar  by  yeast,  both  of  these 
substances  suffer  decomposition  at  the  same 
time,  and  disappear  in  consequence.  But 
|  if  yeast  be  a  body  which  excites  fermenta- 
tion by  being  itself  in  a  state  of  decomposi- 
tion, all  other  matters  in  the  same  condition 
should  have  a  similar  action  upon  sugar;  and 
I  this  is  in  reality  the  case.  Muscle,  urine, 
isinglass,  osmazome,  albumen,  cheese,  glia- 
dine,  gluten,  legumin,  and  blood,  when  in  a 
state  of  putrefaction,  have  all  the  power  of 
producing  the  putrefaction,  or  fermentation 
of  a  solution  of  sugar.  Yeast,  which  by 
continued  washing  has  entirely  lost  the  pro- 
perty of  inducing  fermentation,  regains  it 


CHEMICAL   TRANSFORMATIONS. 


97 


when  its  putrefaction  has  recommenced,  in 
consequence  of  its  being  kept  in  a  warm 
situation  for  some  time. 

Yeast  and  putrefying  animal  and  vegeta- 
ble matters  act  as  peroxide  of  hydrogen  does 
on  oxide  of  silver,  when  they  induce  bodies 
with  which  they  are  in  contact  to  enter  into 
the  same  stale  of  decomposition.  The  dis- 
turbance in  the  attraction  of  the  constituents 
of  the  peroxide  of  hydrogen  effects  a  disturb- 
ance in  the  attraction  of  the  elements  of  the 
oxide  of  silver,  the  one  being  decomposed, 
on  account  of  the  decomposition  of  the 
other. 

Now  if  we  consider  the  process  of  the 
fermentation  of  pure  sugar,  in  a  practical 
point  of  view,  we  meet  with  two  facts  of 
constant  occurrence.  When  the  quantity 
of  ferment  is  too  small  in  proportion  to  that 
of  the  sugar,  its  putrefaction  will  be  com- 
pleted before  the  transformation  of  all  the 
sugar  is  effected.  Some  sugar  here  remains 
undecomposed,  because  the  cause  of  its 
transformation  is  absent,  viz.  contact  with  a 
body  in  a  state  of  decomposition. 

But  when  the  quantity  of  ferment  pre- 
dominates, a  certain  quantity  of  it  remains 
after  all  the  sugar  has  fermented,  its  decom-  | 
position  proceeding  very  slowly,  on  account 
of  its  insolubility  in  water.  This  residue 
of  ferment  is  still  able  to  induce  fermentation 
when  introduced  into  a  fresh  solution  of  su- 
gar, and  retains  the  same  power  until  it  has 
passed  through  all  the  stages  of  its  own 
transformation.  Hence  a  certain  quantity 
/of  yeast  is  necessary  in  order  to  effect  the 
transformation  of  a  certain  portion  of  sugar, 
not  because  it  acts  by  its  quantity  in  increas- 
ing any  affinity,  but  because  its  influence 
depends  solely  on  its  presence,  and  its  pre- 
i  sence  is  necessary,  until  the  last  atom  of 


("""""These  facts  and  observations  point  out  the 
existence  of  a  new  cause,  which  effects 
combinations  and  decompositions.  This 
cause  is  the  action  which  bodies  in  a  state 
of  combination  or  decomposition  exercise 
upon  substances,  the  component  parts  of 
which  are  united  together  by  a  feeble  affinity. 
This  action  resembles  a  peculiar  power,  at- 
tached to  a  body  in  the  state  ot  combination 
or  decomposition,  but  exerting  its  influence 

.^beyond  the  sphere  of  its  own  attractions. 
yVe  are  now  able  to  account  satisfactorily' 
for  many  known  phenomena.  ^ 

A  large  quantity  of  hippuric  acid  mayTJe 
obtained  from  the  fresh  urine  of  a  horse,  by 
the  addition  of  muriatic  acid;  but  when  the 
urine  has  undergone  putrefaction,  no  trace 
of  it  can  be  discovered.     The  urine  of  man 
contains  a  considerable  quantity  of  urea;  ! 
but  when  the  urine  putrefies,  the  urea  en-  j 
tirely  disappears.     When  urea  is  added  to  a 
solution  of  sugar  in  the  slate  of  fermentation., 
it  is  decomposed  into  carbonic  acid  and  am-  ! 
monia.     No  asparagin  can  be  detected  in  a  j 
putrefied   infusion  of  asparagin,  liquorice- 
root,  or  the  root  of  marshra  allow  (Jllthcm 
ojficinalis. 

13 


It  has  already  been  ment  oned,  that  the 
strong  affinity  of  nitrogen  for  hydrogen,  and 
that  of  carbon  for  oxygen,  are  the  cause  of 
the  facility  with  which  the  elements  of  azo- 
tised  compounds  are  disunited ;  those  affini- 
ties aiding  each  other,  inasmuch  as  by  vir- 
tue of  them  different  elements  of  the  com- 
pounds strive  to  take  possession  of  the  dif- 
ferent elements  of  water.  Now  since  it  is 
found  that  no  body  destitute  of  nitrogen  pos- 
sesses, when  pure,  the  property  of  decom- 
posing spontaneously  whilst  in  contact  with 
water,  we  must  ascribe  this  property  which 
azotised  bodies  possess  in  so  eminent  a  de- 
gree, to  something  peculiar  in  the  nature  of 
the  compounds  of  nitrogen,  and  to  their  con- 
stituting, in  a  certain  measure,  more  highly 
organized  atoms. 

Every  azotised  constituent  of  the  animal 
'or  vegetable  organism  runs  spontaneously 
into  putrefaction,  when  exposed  to  moisture 
and  a  high  temperature. 

Azotised  matters  are,  accordingly,  the 
only  causes  of  fermentation  and  putrefaction 
in  vegetable  substances.  "3 

Putrefaction,  on  account  of  its  effects,  as 
a  mixed  transformation  of  many  different 
substances,  may  be  classed  with  the  most 
powerful  processes  of  deoxidation,  by  which 
the  strongest  affinities  are  overcome. 

When  a  solution  of  gypsum  in  water  is 
mixed  with  a  decoction  of  sawdust,  or  any 
other  organic  matter  capable  of  putrefaction, 
and  preserved  in  well-closed  vessels,  it  is 
found  after  some  time,  that  the  solution  con- 
tains no  more  sulphuric  acid,  but  in  its 
place  carbonic  and  free  hydro-sulphuric 
acid,  between  which  the  lime  of  the  gypsum 
is  shared.  In  stagnant  water  containing 
sulphates  in  solution,  crystallised  pyrites  is 
observed  to  form  on  the  decaying  roots. 

Now  we  know  that  in  the  putrefaction  of 
wood  under  water,  when  air  therefore  is  ex- 
cluded, a  part  of  its  carbon  combines  with 
the  oxygen  of  the  water,  as  well  as  with  the 
oxygen  which  the  wood  itself  contains; 
whilst  its  hydrogen  and  that  of  the  decom- 
posed water  are  liberated  either  in  a  pure 
state,  or  as  carburetted  hydrogen.  The 
products  of  this  decomposition  are  of  the 
same  kind  as  those  generated  when  steam  is 
conducted  over  red-hot  charcoal. 

It  is  evident,  that  if  with  the  water  a  sub- 
stance containing  a  large  quantity  of  oxygen, 
such  as  sulphuric  acid,  be  also  present,  the 
matters  in  the  state  of  putrefaction  will  make 
use  of  the  oxygen  of  that  substance  as  well 
as  that  of  the  water,  in  order  to  form  car 
bonic  acid ;  and  the  sulphur  and  hydrogen 
being  set  free  will  combine  whilst  in  the 
nascent  state,  producing  hydrosulphuric 
acid,  which  will  be  again  decomposed  if 
metallic  oxides  be  present ;  and  the  resu  ts 
of  this  second  decomposition  will  be  wa  er 
and  metallic  sulphurets. 

The  putrefied  leaves  of  woad  (Isatis  tinc- 
toria,)  in  contact  with  indigo-blue,  water 
and  alkalies,  suffer  farther  decomposition, 
and  the  indigo  is  deoxidised  and  dissolved. 


98 


AGRICULTURAL   CHEMISTRY. 


The  mannite  formed  by  the  putrefaction 
of  beet-roots  and  other  plants  which  contain 
.sugar,  contains  the  same  number  of  equiva- 
lents of  carbon  and  hydrogen  as  the  sugar 
of  grapes,  but  two  atoms  less  of  oxygen; 
and  it  is  highly  probable  that  it  is  produced 
from  sugar  of  grapes,  contained  in  those 
plants,  in  precisely  the  same  manner  as  in- 
digo-blue is  converted  into  deoxidised  white 
mdigo. 

During  the  putrefaction  of  gluten,  car- 
bonic acid  and  pure  hydrogen  gas  are 
evolved ;  phosphate,  acetate,  caseate,  and 
laetate  of  ammonia  being  at  the  same  time 
produced  in  such  quantity,  that  the  further 
decomposition  of  the  gluten  ceases.  But 
when  the  supply  of  water  is  renewed,  the 
decomposition  begins  again,  and  in  addition 
to  the  salts  just  mentioned,  carbonate  of  am- 
monia and  a  white  crystalline  matter  re- 
sembling mica  (caseous  oxide)  are  formed, 
together  with  hydrosulphate  of  ammonia, 
and  a  mucilaginous  substance  coagulable 
by  chlorine.  Lactic  acid  is  almost  always 
produced  by  the  putrefaction  of  organic 
bodies. 

We  may  now  compare  fermentation  and 
putrefaction  with  the  decomposition  which 
organic  compounds  suffer  under  the  influ- 
ence of  a  high  temperature.  Dry  distilla- 
tion would  appear  to  be  a  process  of  com- 
bustion or  oxidation  going  on  in  the  interior 
of  a  substance,  in  which  a  part  of  the  car- 
bon unites  with  all  or  part  of  the  oxygen  of 
the  compound,  while  other  new  compounds 
containing  a  large  proportion  of  hydrogen 
are  necessarily  produced.  Fermentation 
may  be  considered  as  a  process  of  combus- 
tion or  oxidation  of  a  similar  kind,  taking 
place  in  a  liquid  between  the  elements  of 
the  same  matter,  at  a  very  slightly  elevated 
temperature;  and  putrefaction  as  a  process 
of  oxidation,  in  which  the  oxygen  of  all  the 
substances  present  comes  into  play. 


CHAPTER  VI. 

EREMACAUSIS,  OR   DECAY. 

IN  organic  nature,  besides  the  processes 
of  decomposition  named  fermentation  and 
putrefaction,  another  and  not  less  striking 
class  of  changes  occurs,  which  bodies  suf- 
fer from  the  influence  of  the  air.  This  is 
the  act  of  gradual  combination  of  the  com- 
bustible elements  of  a  body  with  the  oxygen 
of  the  air ;  a  slow  combustion  or  oxidation, 
to  which  we  shall  apply  the  term  of  ere- 
macausis. 

The  conversion  r.f  wood  into  humus,  the 
formation  of  acetic  acid  out  of  alcohol,  ni- 
trification, and  numerous  other  processes, 
are  of  this  nature.  Vegetable  juices  of 
every  kind,  parts  of  animal  and  vegetable 
substances,  moist  sawdust,  blood,  &c.,  can- 
not be  exposed  to  the  air,  without  suffering 
immediately  a  progressive  change  of  colour 


I  and  properties,  during  which  oxygen  is  ab 
!  sorbed.  These  changes  do  not  take  place 
when  water  is  excluded,  or  when  the  sub- 
stances are  exposed  to  the  temperature  of 
32°,  and  it  has  been  observed  that  different 
bodies  require  different  degrees  of  heat,  in 
order  to  effect  the  absorption  of  oxygen, 
and,  consequently,  their  eremacausis.  The 
property  of  suffering  this  change  is  pos- 
sessed in  the  highest  degree  by  substances 
containing  nitrogen. 

When  vegetable  juices  are  evaporated  by 
a.  gentle  heat  in  the  air,  a  brown  or  brown- 
ish-black substance  is  precipitated  as  a  pro 
duct  of  the  action  of  oxygen  upon  them. 
This  substance,  which  appears  to  possess 
similar  properties  from  whatever  juice  it  is 
obtained,  has  received  the  name  of  extractive 
matter;  it  is  insoluble  or  very  sparingly 
soluble  in  water,  but  is  dissolved  with  facil- 
ity by  alkalies.  By  the  action  of  air  on 
solid  animal  or  vegetable  matters,  a  similar 
pulverulent  brown  substance  is  formed,  and 
is  known  by  the  name  of  humus. 

The  conditions  which  determine  the  com 
meneement  of  eremacausis  are  of  various 
kinds.  Many  organic  substances,  particu- 
larly such  as  are  mixtures  of  several  more 
simple  matters,  oxidise  in  the  air  when 
simply  moistened  with  water;  others  not 
until  they  are  subjected  to  the  action  of  al- 
kalies ;  but  the  greatest  part  of  them  undergo 
this  state  of  slow  combustion  or  oxidation, 
when  brought  in  contact  with  other  decay- 
ing matters. 

The  eremacausis  of  an  organic  matter  is 
retarded  or  completely  arrested  by  all  those 
substances  which  prevent  fermentation  or 
putrefaction.  Mineral  acids,  salts  of  mer 
cury,  aromatic  substances,  empyreumatic 
oils,  and  oil  of  turpentine,  possess  a  simi- 
lar action  in  this  respect.  The  latter  sub- 
stances have  the  same  effect  on  decaying 
bodies  as  on  phosphuretted  hydrogen,  the 
spontaneous  inflammability  of  which  they 
destroy. 

Many  bodies  which  do  not  decay  when 
moistened  with  water,  enter  into  eremacau- 
sis when  in  contact  with  an  alkali.  Gallic 
acid,  haematin,  and  many  other  compounds, 
may  be  dissolved  in  water  and  yet  remain 
unaltered  ;  but  if  the  smallest  quantity  of  a 
free  alkali  is  present,  they  acquire  the  pro- 
perty of  attracting  oxygen,  and  are  con- 
verted into  a  brown  substance  like  humus, 
evolving  very  frequently  at  the  same  time 
carbonic  acid.  (Chevreul.) 

A  very  remarkable  kind  of  eremacausis 
takes  place  in  many  vegetable  substances, 
when  they  are  exposed  to  the  influence  of 
air,  water,  and  ammonia.  They  absorb 
oxygen  very  rapidly,  and  form  splendid 
violet  or  red- coloured  liquids,  as  in  the  case 
of  orcin  and  erythrin.  They  now  contain 
an  azotised  substance,  not  in  the  form  of 
ammonia. 

All  these   facts  show  that  the  action  of 
oxygen  seldom  affects  the  carbon  of  decav 
ing  substances,  and  this  corresponds  exactly 


-iREMACAUSIS   OR   DECAY. 


.o  what  happens  in  combustion  at  high  tem- 
peratures. It  is  well  known,  for  example, 
that  when  no  more  oxygen  is  admitted  to  a 
compound  of  carbon  and  hydrogen  than  is 
sufficient  to  combine  with  its  hydrogen,  the 
carbon  is  not  turned,  but  is  separated  as 
lamp-black ;  while,  if  the  quantity  of  oxygen 
is  not  sufficient  even  to  consume  all  the  hy- 
drogen, new  compounds  are  formed,  such 
as  naphthalin  and  similar  matters,  which 
contain  a  smaller  proportion  of  hydrogen 
than  those  compounds  of  carbon  and  hydro- 
gen which  previously  existed  in  the  com- 
bustible substance. 

There  is  no  example  of  carbon  combining 
directly  with  oxygen  at  common  tempera- 
tures, but  numerous  facts  show  that  hydro- 
gen, in  certain  states  of  condensation,  pos- 
sesses that  property.  Lamp-black  which 
has  been  heated  to  redness  may  be  kept  in 
contact  with  oxygen  gas,  without  forming 
carbonic  acid ;  but  lamp-black,  impregnated 
with  oils  which  contain  a  large  proportion 
of  hydrogen,  gradually  becomes  warm,  and 
inflames  spontaneously.  The  spontaneous 
inflammability  of  the  charcoal  used  in  the 
fabrication  of  gunpowder  has  been  correctly 
ascribed  to  the  hydrogen  which  it  contains 
in  considerable  quantity;  for  during  its  re- 
duction to  powder,  no  trace  of  carbonic  acid  I 
can  be  detected  in  the  air  surrounding  it ;  it ! 
is  not  formed  until  the  temperature  of  the  | 
mass  has  reached  a  red  heat.  The  heat 
which  produces  the  inflammation  is  there- 
fore not  caused  by  the  oxidation  of  the  car- 
bon. 

The  substances  which  undergo   erema- 
causis  may  be  divided  into  two  classes.   The  | 
first  class   comprehends    those  substances  i 
which  unite  with  the  oxygen  of  the  air,  | 
without  evolving  carbonic  acid ;    and  the  ! 
second,  such  as  emit  carbonic  acid  by  ab- 
sorbing oxygen. 

When  tne  oil  of  bitter  almonds  is  exposed 
to  the  air,  it  absorbs  two  equivalents  of 
oxygen,  and  is  converted  into  benzoic  acid  ; 
but  half  of  the  oxygen  absorbed  combines 
with  the  hydrogen  of  the  oil,  and  forms 
water,  which  remains  in  union  with  the 
anhydrous  benzoic  acid.* 

*  According  to  the  experiments  of  Dobereiner, 
100  parts  of  pyrogallic  acid  absorbs  38'09  parts  of 
oxygen  when  in  contact  with  ammonia  and  water  ; 
the  acid  being  changed  in  consequence  of  this  ab- 
sorption into  a  mouldy  substance,  which  contains 
less  oxygen  than  the  acid  itself.  It  is  evident  that 
the  substance  which  is  formed  is  not  a  higher 
oxide  ;  and  it  is  found,  on  comparing  the  quantity 
of  the  oxvgen  absorbed  with  that  of  the  hydrogen 
contained  in  the  acid,  that  they  are  exactly  in  the 
proportions  for  forming  water. 

When  colourless  orcin  is  exposed  together  with 
ammonia  to  the  contact  of  oxygen  gas,  the  beau- 
tiful red-coloured  orcein  is  produced.  Now,  the 
only  changes  which  take  place  here  are,  that  the 
absorption  of  oxygen  by  the  elements  of  orcin 
and  ammonia  causes  the  formation  of  water ;  1 
equivalent  of  orcin  CIS  H12  08,  and  1  equivalent 
of  ammonin  NH3,  absorb  5  equivalents  of  oxygen, 
and  5  equivalents  of  water  are  produced,  the  com- 
oosition  of  orcin  being  C18  HlO  O8  N.  (Dumas.) 


But,  although  it  appears  very  probable 
that  the  oxygen  acts  primarily  and  princi- 
pally upon  hydrogen,  the  most  combustible 
constituent  of  organic  matter  in  the  state  of 
decay ;  still  it  cannot  thence  be  concluded 
that  the  carbon  is  quite  devoid  of  the  power 
to  unite  with  oxygen,  when  every  particle 
of  it  is  surrounded  with  hydrogen,  an  ele- 
ment with  which  the  oxygen  combines  with 
greater  facility. 

We  know,  on  the  contrary,  that  although 
nitrogen  cannot  be  made  to  combine  witn 
oxygen  directly,  yet  it  is  oxidized  and  forms 
nitric  acid,  when  mixed  with  a  large  quan- 
tity of  hydrogen,  and  burned  in  oxygen  gas. 
In  this  case  its  affinity  is  evidently  increased 
by  the  combustion  of  the  hydrogen,  which 
is  in  fact  communicated  to  it.  It  is  con- 
ceivable, that  in  a  similar  manner,  the  car- 
bon may  be  directly  oxidised  in  several  cases, 
obtaining  from  its  contact  with  hydrogen  in 
eremacausis  a  property  which  it  does  not 
itself  possess  at  common  temperatures.  But 
the  formation  of  carbonic  acid  during  the 
eremacausis  of  bodies  containing  hydrogen, 
must  in  most  cases  be  ascribed  to  another 
cause.  It  appears  to  be  formed  in  a  man- 
ner similar  to  the  formation  of  acetic  acid, 
by  the  eremacausis  of  saliculite  of  potash.* 

An  alkaline  solution  of  haematin  being 
exposed  to  an  atmosphere  of  oxygen,  0-2 
grm.  absorb  28'6  cubic  centimetres  of  oxy- 
gen gas  in  twenty-four  hours,  the  alkali  ac 
quiring  at  the  same  time  6  cubic  centimetres 
of  carbonic  acid.  (Chevreul.)  But  these 
6  cubic  centimetres  of  carbonic  acid  contain 
only  an  equal  volume  of  oxygen,  so  that  il 
is  certain  from  this  experiment  that  $  of  the 
oxygen  absorbed  have  not  united  with  the 
carbon.  It  is  highly  probable,  that  during 
the  oxidation  of  the  hydrogen,  a  portion  of 
the  carbon  had  united  with  the  oxygen  con- 
tained in  the  haematin,  and  had  separated 
from  the  other  elements  as  carbonic  acid. 

The  experiments  of  De  Saussure  upon 
the  decay  of  woody  fibre  show  that  such  a 
separation  is  quite  possible.  Moist  woody 
fibre  evolved  one  volume  of  carbonic  acid 
for  every  volume  of  oxygen  which  it  ab- 
sorbed. It  has  just  been  mentioned  that 
carbonic  acid  contains  its  own  volume  of 
oxygen.  Now,  woody  fibre  contains  carbon 
and  the  elements  of  water,  so  that  the  result 
of  the  action  of  oxygen  upon  it  is  exactly 
the  same  as  if  pure  charcoal  had  combined 
directly  with  oxygen.  But  the  characters 
of  woody  fibre  show,  that  the  elements  of 
water  are  not  contained  in  it  in  the  form  of 
water;  for,  were  this  the  case,  starch,  sugar, 
and  gum  must  also  be  considered  as  hydrates 
of  carbon. 

In  this  case  it  is  evident,  that  the  oxygen  absorbed 
has  united  merely  with  the  hydrogen. 

*  This  salt,  when  exposed  to  a  moist  atmo- 
sphere, absorbs  3  atoms  of  oxygen  ;  melanic  acid 
is  produced,  a  body  resembling  humus,  in  conse- 
quence of  the  formation  of  which,  the  elements 
of  1  atom  of  acetic  acid  are  separated  from  the 
saliculous  acid. 


100 


AGRICULTURAL   CHEMISTRY. 


But  if  the  hydrogen  does  not  exist  in 
woody  fibre  in  the  form  of  water,  the  direct 
oxidation  of  the  carbon  cannot  be  considered 
as  at  all  probable,  without  rejecting  all  the 
facts  established  by  experiment  regarding 
the  process  of  combustion  at  low  tempera- 
tures. t 

If  we  examine  the  action  of  oxygen  upon 
a  substance  containing  a  large  quantity  of 
hydrogen,  such  as  alcohol,  we  find  most 
distinctly,  that  the  direct  formation  of  car- 
bonic acid  is  the  last  stage  of  its  oxidation, 
and  that  it  is  preceded  by  a  series  of  changes, 
the  last  of  which  is  a  complete  combustion 
of  the  hydrogen  Aldehyde,  acetic,  formic, 
oxalic,  and  carbonic  acids,  form  a  connected 
chain  of  products  arising  from  the  oxidation 
of  alcohol;  and  the  successive  changes 
which  this  fluid  experiences  from  the  action 
of  oxygen  may  be  readily  traced  in  them. 
Aldehyde  is  alcohol  minw  hydrogen;  acetic 
acid  is  formed  by  the  direct  union  of  alde- 
hyde with  oxygen.  Formic  acid  and  water 
tire  formed  by  the  union  of  acetic  acid  with 
oxygen.  When  all  the  hydrogen  is  removed 
from  this  formic  acid,  oxalic  acid  is  pro- 
duced ;  and  the  latter  acid  is  converted  into 
carbonic  acid  by  uniting  with  an  additional 
portion  of  oxygen.  All  these  products 
appear  to  be  formed  simultaneously,  by  the 
action  of  oxidising  agents  on  alcohol ;  but 
it  can  scarcely  be  doubted,  that  the  forma- 
tion of  the  last  product,  the  carbonic  acid, 
does  not  take  place  until  all  the  hydrogen 
has  been  abstracted. 

The  absorption  of  oxygen  by  drying  oils 
certainly  does  not  depend  upon  the  oxida- 
tion of  their  carbon ;  for  in  raw  nut-oil,  for 
example,  which  was  not  free  from  mucilage 
and  other  substances,  only  twenty-one  vo- 
lumes of  carbonic  acid  were  formed  for 
every  146  volumes  of  oxygen  gas  absorbed. 

It  must  be  remembered,  that  combustion 
or  oxidation  at  low  temperatures  produces 
results  quite  similar  to  combustion  at  high 
temperatures  with  limited  access  of  air.  The 
most  combustible  element  of  a  compound, 
which  is  exposed  to  the  action  of  oxygen, 
must  become  oxidised  first,  for  its  superior 
i  combustibility  is  caused  by  its  being  enabled 
to  unite  with  oxygen  at  a  temperature  at 
which  the  other  elements  cannot  enter  into 
that  combination ;  this  property  having  the 
same  effect  as  a  greater  affinity. 

The  combustibility  of  potassium  is  no 
measure  for  its  affinity  for  oxygen;  we  have 
reason  to  believe  that  the  attraction  of  mag- 
nesium and  aluminium  for  oxygen  is  greater 
than  that  of  potassium  for  the  same  element; 
but  neither  of  those  metals  oxidises  either 
in  air  or  water  at  common  temperatures 
wnilst  potassium  decomposes  water  with 
great  violence,  and  appropriates  its  oxygen. 

Phosphorus  and  hydrogen  combine  with 
oxygen  at  ordinary  temperatures,  the  first 
in  moist  air,  the  second  when  in  contact 
with  finely-divided  platinum  ;  while  char- 
coal requires  a  red  heat  before  it  can  enter 
into  combination  with  oxygen.  It  is  evi- 


dent that  phosphorus  and  hyorogen  are 
more  combustible  than  charcoal,  that  is,  that 
neir  affinity  for  oxygen  at  common  tempera- 
ures  is  greater;  and  this  is  not  the  less  cer- 
ain,  because  it  is  found,  that  carbon  in  cer- 
tain other  conditions  shows  a  much  greater 
affinity  for  oxygen  than  either  of  tnose  sub- 
stances. 

In  putrefaction,  the  conditions  are  evi« 
dently  present,  under  which  the  affinity  of 
carbon  for  oxygen  comes  into  play;  neither 
expansion,  cohesion,  nor  the  gaseous  state, 
opposes  it,  whilst  in  eremacausis  all  these 
restraints  have  to  be  overcome. 

The  evolution  of  carbonic  acid,  during 
the  decay  or  eremacausis  of  animal  or  vege- 
table bodies  which  are  rich  in  hydrogen, 
must  accordingly  be  ascribed  to  a  transposi- 
tion of  the  elements  or  disturbance  in  their 
attractions,  similar  to  that  which  gives  rise 
to  the  formation  of  carbonic  acid  in  the  pro- 
cesses of  fermentation  'and  putrefaction. 

The  eremacausis  of  such  substances  is, 
therefore,  a  decomposition  analogous  to  the 
putrefaction  of  azotised  bodies.  For  in  these 
there  are  two  affinities  at  play ;  the  affinity 
of  nitrogen  for  hydrogen,  and  that  of  carbon 
for  oxygen,  and  both  facilitate  the  disunion 
of  the  elements.  Now  there  are  two  affini- 
ties also  in  action  in  those  bodies  whicn  de- 
cay with  the  evolution  of  carbonic  acid. 
One  of  these  affinities  is  the  attraction  of  the 
oxygen  of  the  air  for  the  hydrogen  of  the 
substance,  which  corresponds  to  Ihe  attrac- 
tion of  nitrogen  for  the  same  element ;  and 
the  other  is  the  affinity  of  the  carbon  of  the 
substance  for  its  oxygen,  which  is  constant 
under  all  circumstances. 

When  wood  putrefies  in  marshes,  carbon 
and  oxygen  are  separated  from  its  elements 
in  the  form  of  carbonic  acid,  and  hydrogen 
in  the  form  of  carburetted  hydrogen.  But 
when  wood  decays  or  putrefies  in  the  air, 
its  hydrogen  does  not  combine  with  carbon, 
but  with  oxygen,  for  which  it  has  a  much 
greater  affinity  at  common  temperatures. 

Now  it  is  evident  from  the  complete  simi- 
larity of  these  processes,  that  decaying  and 
putrefying  bodies  can  mutually  replace  one 
another  in  their  reciprocal  actions. 

All  putrefying  bodies  pass  into  the  state 
of  decay,  when  exposed  freely  to  the  air, 
and  all  decaying  matters  into  that  of  putre- 
faction when  air  is  excluded.  All  bodies, 
likewise,  in  a  state  of  decay  are  capable  of 
inducing  putrefaction  in  other  bodies  in  the 
same  manner  as  putrefying  bodies  them 
selves  do. 


CHAPTER  VII. 

EREMACAITSIS  OR  DECAY  OP  BODIES  DESTI- 
TUTE OF  NITROGEN:  FORMATION  OF  ACETIC 
ACID. 

ALL  those  substances  which   appear   to 
possess  the  property  of  entering  spontar.e- 


EREMACAUSIS   OR   DECAY. 


101 


ously  into  fermentation  and  putrefaction,  do 
not  in  reality  suffer  those  changes  without 
some  previous  disturbance  in  the  attraction 
of  their  elements.  Eremacausis  always  pre- 
cedes fermentation  and  putrefaction,  and  it 
is  not  until  after  the  absorption  of  a  certain 
quantity  of  oxygen  that  the  signs  of  a  trans- 
formation in  the  interior  of  the  substances 
show  themselves. 

It  is  a  very  general  error  to  suppose  that 
organic  substances  have  the  power  of  un- 
dergoing change  spontaneously,  without  the 
aid  of  an  external  cause.  When  they  are 
not  in  a  state  of  change,  it  is  necessary,  be- 
fore they  can  assume  that  state,  that  the 
existing  equilibrium  of  their  elements  should 
be  disturbed ;  and  the  most  common  cause 
of  this  disturbance  is  undoubtedly  the  atmo- 
sphere which  surrounds  all  bodies. 

The  juices  of  the  fruit  or  other  part  of  a 
plant  which  very  readily  undergo  decompo- 
sition, retain  their  properties  unchanged  as 
long  as  they  are  protected  from  immediate 
contact  with  the  air,  that  is,  as  long  as  the 
cells  or  organs  in  which  they  are  contained 
resist  the  influence  of  the  air.  It  is  not 
until  after  the  juices  have  been  exposed  to 
the  air,  and  have  absorbed  a  certain  quan- 
tity of  cxygen,  that  the  substances  dissolved 
in  them  begin  to  be  decomposed. 

The  beautiful  experiments  of  Gay-Lussac 
upon  the  fermentation  of  the  juice  of  grapes, 
as  well  as  the  important  practical  improve- 
ments to  which  they  have  led,  are  the  best 
proofs  that  the  atmosphere  possesses  an  in- 
fluence upon  the  changes  of  organic  sub- 
stances. The  juice  of  grapes  which  were 
expressed  under  a  receiver  filled  with  mer- 
cury, so  that  air  was  completely  excluded, 
did  not  ferment.  But  when  the  smallest 
portion  of  air  was  introduced,  a  certain 
quantity  of  oxygen  became  absorbed,  and 
fermentation  immediately  began.  Although 
the  juice  was  expressed  from  the  grapes  in 
contact  with  air,  under  the  conditions  there- 
fore necessary  to  cause  its  fermentation,  still 
this  change  did  not  ensue  when  the  juice 
was  heated  in  close  vessels  to  the  tempera- 
ture of  boiling  water.  When  thus  treated, 
it  could  be  preserved  for  years  without 
losing  its  property  of  fermenting.  A  fresh 
exposure  to  the  air  at  any  period  caused  it 
to  ferment. 

Animal  food  of  every  kind,  and  even  the 
most  delicate  vegetables,  may  be  preserved 
unchanged  if  heated  to  the  temperature  of 
boiling  water  in  vessels  from  which  the  air 
is  completely  excluded.  Food  thus  pre- 
pared has  been  kept  for  fifteen  years,  and 
upon  opening  the  vessels  after  this  long 
time,  has  been  found  as  fresh  and  well-fla- 
voured as  when  originally  placed  in  them. 

The  action  of  the  oxygen  in  these  pro- 
cesses of  decomposition  is  very  simple ;  it 
excites  changes  in  the  composition  of  the 
azotised  matters  dissolved  in  the  juices; — 
the  mode  of  combination  of  the  elements  of 
those  matters  undergoes  a  disturbance  and 
change  in  conse  \uence  of  their  contac  with 


|  oxygen.  The  oxygen  acts  here  m  a  similar 
!  manner  to  the  friction  or  motion  which  af- 
fects the  mutual  decomposition  of  two  salts, 
the  crystallization  of  salts  from  their  solution, 
or  the  explosion  of  fulminating  mercury.  It 
causes  the  state  of  rest  to  be  converted  into 
a  state  of  motion. 

When  this  condition  of  intestine  motion 
is  once  excited,  the  presence  of  oxygen  is 
no  longer  necessary.  The  smallest  particle 
of  an  azotised  body  in  this  act  of  decompo- 
sition exercises  an  influence  upon  the  parti- 
ticles  in  contact  with  it,  and  the  state  of 
motion  is  thus  propagated  through  the  sub- 
stance. The  air  may  now  be  completely 
excluded,  but  the  fermentation  or  putrefac- 
tion proceeds  uninterruptedly  to  its  comple- 
tion. It  has  been  remarked  that  the  mere 
contact  of  carbonic  acid  is  sufficient  to  pro- 
duce fermentation  in  the  juices  of  several 
fruits. 

The  contact  of  ammonia  and  alkalies  in 
general  may  be  mentioned  amongst  the 
chemical  conditions  which  determine  the 
commencement  of  eremacausis ;  for  their 
presence  causes  many  substances  to  absorb 
oxygen  and  to  decay,  in  which  neither  oxy- 
gen nor  alkalies  alone  produce  that  change. 

Thus  alcohol  does  not  combine  with  the 
oxygen  of  the  air  at  common  temperatures. 
But  a  solution  of  potash  in  alcohol  absorbs 
oxygen  with  much  rapidity,  and  acquires  a 
brown  colour.  The  alcohol  is  found  after  a 
short  time  10  contain  acetic  acid,  formic  acid, 
and  the  products  of  the  decomposition  of 
aldehyde  by  alkalies,  including  aldehyde 
resin,  which  gives  the  liquid  a  brown  colour. 

The  most  general  condition  for  the  pro- 
duction of  eremacausis  in  organic  matter  is 
contact  with  a  body  already  in  the  state  of 
eremacausis  or  putrefaction.  We  have  here 
an  instance  of  true  contagion;  for  the  com- 
munication of  the  state  of  combustion  is  in 
reality  the  effect  of  the  contact. 

It  is  decaying  wood  which  causes  fresh 
wood  around  it  to  assume  the  same  condi- 
tion, and  it  is  the  very  finely  divided  woody 
fibre  in  the  act  of  decay  which  in  moistened 
gall-nuts  converts  the  tannic  acid  with  such 
rapidity  into  gallic  acid. 

A  most  remarkable  and  decided  example 
of  this  induction  of  combustion  has  been 
observed  by  De  Saussure.  It  has  already 
been  mentioned,  that  moist  woody  fibre, 
cotton,  silk,  or  vegetable  mould,  in  the  act 
of  fermentation  or  putrefaction,  converts 
oxygen  gas  which  may  surround  it  into  car- 
bonic acid,  without  change  of  volume.  New, 
De  Saussure  added  a  certain  quantity  of  hy- 
drogen gas  to  the  oxygen,  and  observed  a 
diminution  in  volume  immediately  after  the 
addition.  A  part  of  the  hydrogen  gras  had 
disappeared,  and  along  with  it  a  portion  of 
the  oxygen,  but  a  corresponding  quantity 
of  carbonic  acid  gas  had  not  been  formed. 
The  hydrogen  and  oxygen  had  disappeared 
in  exactly  the  same  proportion  as  that  in 
which  they  combine  to  form  water;  a  true 
combustion  of  the  hydrogen,  therefore,  had 


102 


AGRICULTURAL   CHEMISTRY. 


been  induced  by  mere  contact  with  matter 
in  the  state  of  eremacausis.  The  action  of 
the  decaying  substance  here  produced  results 
exactly  similar  to  those  effected  by  spongy 
platinum;  but  that  they  proceeded  from  a 
different  cause  was  shown  by  the  fact,  that 
the  presence  of  carbonic  oxide,  which  ar- 
rests completely  the  action  of  platinum 
on  carburetted  hydrogen,  did  not  retard  in 
the  slightest  degree  the  combustion  of 
the  hydrogen  in  contact  with  the  decaying 
bodies. 

But  the  same  bodies  were  found  by  De 
Saussure  not  to  possess  the  property  just 
described,  before  they  were  in  a  state  of  fer- 
mentation or  decay ;  and  he  has  shown  that 
even  when  they  are  in  this  state,  the  pre- 
sence of  antiseptic  matter  destroys  com- 
pletely all  their  influence. 

Let  us  suppose  a  volatile  substance  con- 
taining a  large  quantity  of  hydrogen  to  be 
substituted  for  the  hydrogen  gas  in  DeSaus- 
sure's  experiments.  Now,  the  hydrogen  in 
such  compounds  being  contained  in  a  state 
of  greater  condensation  would  suffer  a  more 
rapid  oxidation,  that  is,  its  combustion 
would  be  sooner  completed.  This  principle 
is  in  reality  attended  10  in  the  manufactories 
in  which  acetic  acid  is  prepared  according 
to  the  new  plan.  In  the  process  there 
adopted  all  the  conditions  are  afforded  for  the 
eremacausis  of  alcohol,  and  for  its  conse- 
quent conversion  into  acetic  acid. 

The  alcohol  is  exposed  to  a  moderate 
heat,  and  spread  over  a  very  extended  sur- 
face, but  these  conditions  are  not  sufficient 
to  effect  its  oxidation.  The  alcohol  must  be 
mixed  with  a  substance  which  is  with  faci- 
lity changed  by  the  oxygen  of  the  air,  and 
either  enters  into  eremacausis  by  mere  con- 
tact with  oxygen,  or  by  its  fermentation  or 
putrefaction  yields  products  possessed  of  this 
property.  A  small  quantity  of  beer,  aces- 
cent wine,  a  decoction  of  malt,  honey,  and 
numerous  other  substances  of  this  kind, 
possess  the  action  desired. 

The  difference  in  the  nature  of  the  sub- 
stances which  possess  this  property  shows, 
that  none  of  them  can  contain  a  peculiar 
matter  which  has  the  property  of  exciting 
^remacausis ;  they  are  only  the  bearers  of  an 
action,  the  influence  of  which  extends  be- 
yond the  sphere  of  its  own  attractions. 
Their  power  consists  in  a  condition  of  de- 
composition or  eremacausis,  which  im- 
presses the  same  condition  upon  the  atoms 
of  alcohol  in  its  vicinity  ;  exactly  as  in  the 
case  of  an  alloy  of  platinum  and  silver  dis- 
solving in  nitric  acid,  in  which  the  platinum 
becomes  oxidised,  by  virtue  of  an  inductive 
action  exercised  upon  it  by  the  silver  in  the 
act  of  its  oxidation.  The  hydrogen  of  the 
alcohol  is  oxidised  at  the  expense  of  the 
oxygen  in  contact  with  it,  and  forms  water, 
evolving  heat  at  the  same  time;  the  residue 
is  aldehyde,  a  substance  which  has  as  great 
an  affinity  for  oxygen  as  sulphuric  acid,  and 
combines,  therefore,  directly  with  it,  pioduc- 
ing  acetic  acid. 


CHAPTER  VIII. 

EREMACAUSIS    OF   SUBSTANCES    CONTAINING 
NITROGEN.       NITRIFICATION. 

WHEN  azotised  substances  are  burned  at 
high  temperatures,  their  nitrogen  does  not 
enter  into  direct  combination  with  oxygen. 
The  knowledge  of  this  fact  is  of  assistance 
in  considering  the  process  of  the  eremacau- 
sis of  such  substances.  Azotised  organic 
matter  always  contains  carbon  and  hydro- 
gen, both  of  which  elements  have  a  very 
strong  affinity  for  oxygen. 

Now  nitrogen  possesses  a  very  feeble 
affinity  for  that  element,  so  that  its  com- 
pounds during  their  combustion  present 
analogous  phenomena  to  those  which  are 
observed  in  the  combustion  of  substances 
containing  a  large  proportion  of  hydrogen 
and  carbon ;  a  separation  of  the  carbon  of 
the  latter  substances  in  an  uncombined  state 
takes  place,  and  in  the  same  way  the  sub- 
stances containing  nitrogen  give  out  that 
element  in  its  gaseous  form. 

When  a  moist  azotised  animal  matter  is 
exposed  to  the  action  of  the  air,  ammonia  is 
always  liberated  ;  nitric  acid  is  never  formed. 

But  when  alkalies  or  alkaline  bases  are 
present,  a  union  of  oxygen  with  the  nitrogen 
takes  place  under  the  same  circumstances, 
and  nitrates  are  formed  together  with  the 
other  products  of  oxidation. 

Although  we  see  the  most  simple  means 
and  direct  methods  employed  in  the  great 
processes  of  decomposition  which  proceed 
in  nature,  still  we  find  that  the  final  result 
depends  on  a  succession  of  actions,  which 
are  essentially  influenced  by  the  chemical  na- 
ture of  the  bodies  submitted  to  decomposition. 

When  it  is  observed  that  the  character  of 
a  substance  remains  unaltered  in  a  whole 
series  of  phenomena,  there  is  no  reason  to 
ascribe  a  new  character  to  it,  for  the  pur- 
pose of  explaining  a  single  phenomenon, 
especially  where  the  explanation  of  that  ac- 
cording to  known  facts  offers  no  difficulty. 

The  most  distinguished  philosophers  sup- 
pose that  the  nitrogen  in  an  animal  sub- 
stance, when  exposed  to  the  action  of  air, 
water,  and  alkaline  bases,  obtains  the  power 
to  unite  directly  with  oxygen,  and  form  ni- 
tric acid,  but  we  are  not  acquainted  with  a 
single  fact  which  justifies  this  opinion.  It 
is  only  by  the  interposition  of  a  large  quan- 
tity of  hydrogen  in  the  state  of  combustion 
or  oxidation,  that  nitrogen  can  be  converted 
into  an  oxide. 

When  a  compound  of  nitrogen  and  cai 
bon,  such  as  cyanogen,  is  burned  in  oxygeu 
gas,  its  carbon  alone  is  oxidised ;  and  when 
it  is  conducted  over  a  metallic  oxide  heated 
to  redness,  an  oxide,  of  nitrogen  is  very 
rarely  produced,  and  never  when  the  carbon 
is  in  excess.  Kuhlmann  found  in  his  ex 
periments,  that  it  was  only  when  cyanogen 
[  was  mixed  with  an  excess  of  oxygen  gas 
and  conducted  over  spongy  platinum,  that 
nitric  acid  was  generated. 


EREMACAU3I3   OR    DECAY. 


103 


Kuhlmanu  coull  not  succeed  in  causing  | 
pure  nitrogen  to  combine  directly  with  oxy- 
gen, even  under  the  most  favourable  circum- 
stances ;  thus,  with  the  aid  of  spongy  plati- 
num at  different  temperatures,  no  union 
took  place. 

The  carbon  in  the  cyanogen  gas  must, 
therefore,  have  given  rise  to  the  combustion 
of  the  nitrogen  by  induction. 

On  the  other  hand  we  find  that  ammonia 
(a  compound  of  hydrogen  and  nitrogen) 
cannot  be  exposed  to  the  action  of  oxygen, 
without  the  formation  of  an  oxide  of  nitro- 
gen, and  in  consequence  the  production  of 
nitric  acid. 

It  is  owing  to  the  great  facility  with  which 
ammonia  is  converted  into  nitric  acid,  that 
it  is  so  difficult  to  obtain  a  correct  determi- 
nation of  the  quantity  of  nitrogen  in  a  com- 
pound subjected  to  analysis,  in  which  it  is 
either  contained  in  the  form  of  ammonia,  or 
from  which  ammonia  is  formed  by  an  eleva- 
tion of  temperature.  For  when  ammonia  is 
passed  over  red-hot  oxide  of  copper,  it  is 
converted,  either  completely  or  partially, 
into  binoxide  of  nitrogen. 

When  ammoniacal  gas  is  conducted  over 
peroxide  of  manganese  or  iron  heated  to 
redness,  a  large  quantity  of  nitrate  of  ammo- 
nia is  obtained,  if  the  ammonia  be  in  excess ; 
and  the  same  decomposition  happens  when 
ammonia  and  oxygen  are  together  passed 
over  red-hot  spongy  platinum. 

It  appears,  therefore,  that  the  combination 
of  oxygen  with  nitrogen  occurs  rarely  during 
the  combustion  of  compounds  of  the  latter 
element  with  carbon,  but  that  nitric  acid  is 
always  a  product  when  ammonia  is  present 
in  the  substance  exposed  to  oxidation. 

The  cause  wherefore  the  nitrogen  in  am- 
monia exhibits  such  a  strong  disposition  to 
become  converted  into  nitric  acid  is  un- 
doubtedly that  the  two  products,  which  are 
the  result  of  the  oxidation  of  the  constituents 
of  ammonia,  possess  the  power  of  uniting 
with  one  another.  Now  this  is  not  the  case 
in  the  combustion  of  compounds  of  carbon 
and  nitrogen  ;  here  one  of  the  products  is 
carbonic  acid,  which,  on  account  of  its 
gaseous  form,  must  oppose  the  combination 
of  the  oxygen  and  nitrogen,  by  preventing 
their  mutual  contact,  while  the  superior 
•affinity  of  its  carbon  for  the  oxygen  during 
the  act  of  its  formation  will  aid  this  effect. 

When  sufficient  access  of  air  is  admitted 
during  the  combustion  of  ammonia,  water 
is  formed  as  well  as  nitric  acid,  and  both  of 
these  bodies  combine  together.  The  pre- 
sence of  water  may,  indeed,  be  considered  as 
one  of  the  conditions  essential  to  nitrification, 
since  nitric  acid  cannot  exist  without  it. 

Eremacausis  is  a  kind  of  putrefaction,  dif- 
fering from  the  common  process  of  putrefac- 
tion, only  in  the  part  which  the  oxygen  of  the 
air  plays  in  the  transformations  of  the  body  in 
decay.  When  this  is  remembered,  and  when 
it  is  considered  that  in  the  transposition  of  the 
elements  of  azotis.'d  bodies  their  nitrogen  as- 
sumes the  form  of  ammonia,  and  that  in  this 


form,  nitrogen  possesses  a  much  greater  dis- 
position to  unite  with  oxygen  than  it  has  in 
any  of  its  other  compounds ;  we  can  with 
difficulty  resist  the  conclusion,  that  ammo- 
nia is  the  general  cause  of  nitrification  on 
the  surface  of  the  earth. 

Azotised  animal  matter  is  not,  therefore, 
the  immediate  cause  of  nitrification,  it  con- 
tributes to  the  production  of  nitric  acid  only 
in  so  far  as  it  is  a  slow  and  continued  source 
of  ammonia. 

Now  it  has  been  shown  in  the  former  part 
of  this  work,  that  ammonia  is  always  pre- 
sent in  the  atmosphere,  so  that  nitrates 
might  thence  be  formed  in  substances  which 
themselves  contained  no  azotised  matter.  It 
is  known  also,  that  porous  substances  pos- 
sess generally  the  power  of  condensing  am- 
monia; there  are  few  ferruginous  earths 
which  do  not  evolve  ammoniacal  products 
when  heated  to  redness,  and  ammonia  is  the 
cause  of  the  peculiar  smell  perceived  upon 
moistening  aluminous  minerals.  Thus,  am- 
monia, by  being  a  constituent  of  the  atmo- 
sphere, is  a  very  widely  diffused  cause  of 
nitrification,  which  will  come  into  play 
whenever  the  different  conditions  necessary 
for  the  oxidation  of  ammonia  are  combined. 
It  is  probable  that  other  organic  bodies  in 
the  state  of  eremacausis  are  the  means  of 
causing  the  combustion  of  ammonia ;  at  all 
events,  the  cases  are  very  rare,  in  which 
nitric  acid  is  generated  from  ammonia,  in 
the  absence  of  all  matter  capable  of  erema- 
causis. 

From  the  preceding  observations  on  the 
causes  of  fermentation,  putrefaction,  and  de- 
cay, we  may  now  draAV  several  conclusions 
calculated  to  correct  the  views  generally  en- 
tertained respecting  the  fermentation  of  wine 
and  beer,  and  several  other  important  pro- 
cesses of  decomposition  which  occur  in 
nature. 


CHAPTER  IX. 

ON    VINOUS    FERMENTATION  : —  WINE    AND 
BEER. 

IT  has  already  been  mentioned,  that  fer- 
mentation is  excited  in  the  juice    of  grapes 
by  the  access  of  air ;  alcohol  and  carbonic 
acid  being  formed  by  the  decomposition  of 
|  the  sugar  contained  in  the  fluid.  But  it  was 
I  also  stated,  that  the  process  once  commenced, 
continues  until  all  the  sugar  is  completely 
|  decomposed,   quite    independently  of  any 
further  influence  of  the  air. 

In  addition  to  the  alcohol  ana*  carbonic 
acid  formed  by  the  fermentation  of  the 
juice,  there  is  also  produced  a  yellow  or 
gray  insoluble  substance,  containing  a  large 
quantity  of  nitrogen.  It  is  this  body  which 
possesses  the  power  of  inducing  fermenta- 
tion in  a  new  solution  of  sugar,  and  which 
has  in  consequence  received  the  name  of 
ferment. 


1(4 


AGRICULTURAL   CHEMISTRY. 


The  alcohol  and  carbonic  acid  are  pro- 
duced from  the  elements  of  the  sugar,  and 
tne  ferment  from  those  azotised  constituents 
of  the  grape -juice,  which  have  been  termed 
gluten,  or  vegetable  albumen. 

According  to  the  experiments  of  De 
Saussure,  fresh  impure  gluten  evolved,  in 
five  weeks,  twenty-eight  times  its  volume  of 
a  gas  which  consisted  f  of  carbonic  acid, 
and  £  of  pure  hydrogen  gas  ;  ammoniacal 
salts  of  several  organic  acids  were  formed 
at  the  same  time.  Water  must,  therefore, 
Le  decomposed  during  the  putrefaction  of 
gluten  ;  the  oxygen  of  this  water  must  enter 
into  combination  with  some  of  its  consti- 
tuents, whilst  hydrogen  is  liberated,  a  cir- 
cumstance which  happens  only  in  decom- 
positions of  the  most  energetic  kind.  Nei- 
ther ferment  nor  any  substance  similar  to  it 
is  formed  in  this  case ;  and  we  have  seen 
that  in  the  fermentation  of  saccharine  vege- 
table juices,  no  escape  of  hydrogen  gas  takes 
place. 

It  is  evident  that  the  decomposition  which 
gluten  suffers  in  an  isolated  state,  and  that 
which  it  undergoes  when  dissolved  in  a  ve- 
getable juice,  belong  to  two  different  kinds 
of  transformations.  There  is  reason  to  be- 
lieve that  its  change  to  the  insoluble  state 
depends  upon  an  absorption  of  oxygen,  for 
its  separation  in  this  state  may  be  effected, 
nnder  certain  conditions,  by  free  exposure 
'«.  tho  a;r,  without  the  presence  of  ferment- 
ing sugar.  It  is  known  also  that  the  juice 
of"  grapes,  or  vegetable  juices  in  general, 
become  turbid  when  in  contact  with  air,  be- 
fore fermentation  commences  ;  and  this  tur- 
bidity is  owing  to  the  formation  of  an  inso- 
luble precipitate  of  the  same  nature  as  fer- 
ment. 

From  the  phenomena  which  have  been 
observed  during  the  fermentation  of  wort,*  it 
is  known  with  perfect  certainty- that  ferment 
is  formed  from  gluten  at  the  same  time  that 
the  transformation  of  the  sugar  is  effected  ; 
for  the  wort  contains  the  azotised  matter  of 
the  corn,  namely,  gluten  in  the  same  condi- 
tion as  it  exists  in  the  juice  of  grapes.  The 
wort  ferments  by  the  addition  of  yeast,  but 
after  its  decomposition  is  completed,  the 
quantity  of  ferment  or  yeast  is  found  to  be 
thirty  times  greater  than  it  was  originally. 

Yeast  from  beer  and  that  from  wine,  ex- 
amined under  the  microscope,  present  the 
/  same  form  and  general  appearance.  They 
are  both  acted  on  in  the  same  manner  by 
alkalies  and  acids,  and  possess  the  power  of 
inducing  fermentation  anew  in  a  solution  of 
sugar ;  in  short,  they  must  be  considered 
as  identical. 

The  fact  that  water  is  decomposed  during 
the  putrefaction  of  gluten  has  been  com- 
pletely proved.  The  tendency  of  the  carbon 
of  the  gluten  to  appropriate  the  oxygen  of 
water  must  also  always  be  in  action,  whether 
the  gluten  is  decomposed  in  a  soluble  or  in- 

*  Wort  is  an  infusion  of  malt ;  it  consists  of  the       *  The  liquid  expressed  from  grapes  when  fully 
noluble  parts  of  this  substance  dissolved  in  water,  i  ripe  is  called  must. 


soluble  state.  These  considerations,  there- 
fore, as  well  as  the  circumstance  which  al) 
the  experiments  made  on  this  subject  appear 
to  point  out,  that  the  conversion  of  gluten 
to  the  insoluble  state  is  the  result  of  oxida- 
tion, lead  us  to  conclude  that  the  oxygen 
consumed  in  this  process  is  derived  from  the 
elements  of  water,  or  from  the  sugar  which 
contains  oxygen  and  hydrogen  in  the  same 
proportion  as  water.  At  all  events,  the  oxy 
gen  thus  consumed  in  the  fermentation  of 
wine  and  beer  is  not  taken  from  the  atmo 
sphere. 

The  fermentation  of  pure  sugar  in  con 
tact  with  yeast  must  evidently  be  a  very  dif- 
ferent process  from  the  fermentation  of 
wort  or  must.* 

In  the  former  case,  the  yeast  disappears 
during  the  decomposition  of  sugar ;  but  in 
the  latter,  a  transformation  of  gluten  is 
effected  at  the  same  time,  by  which  ferment 
is  generated.  Thus  yeast  is  destroyed  in  the 
one  case,  but  is  formed  in  the  other. 

Now  since  no  free  hydrogen  gas  can  be 
detected  during  the  fermentation  of  beer  and 
wine,  it  is  evident  that  the  oxidation  of  the 
gluten,  that  is,  its  conversion  into  ferment, 
must  take  place  at  the  cost  either  of  the  oxy- 
gen of  the  water,  or  of  that  of  the  sugar ; 
whilst  the  hydrogen  which  is  set  free  must 
enter  into  new  combinations,  or  by  the  de- 
oxidation  of  the  sugar,  new  compounds  con- 
taining a  large  proportion  of  hydrogen,  and 
small  quantity  of  oxygen,  together  with  the 
carbon  of  the  sugar,  must  be  formed. 

It  is  well  known  that  wine  and  fermented 
liquors  generally  contain,  in  addition  to  the 
alcohol,  other  substances  which  could  not 
be  detected  before  their  fermentation,  and 
which  must  have  been  formed,  therefore, 
during  that  process  in  a  manner  similar  to 
the  production  of  mannite.  The  smell  and 
taste  which  distinguished  wine  from  all 
other  fermented  liquids  are  known  to  depend 
upon  an  ether  of  a  volatile  and  highly  com- 
bustible acid  ;  the  ether  is  of  an  oily  nature, 
and  has  received  the  name  (Enanthic  ether. 
It  is  also  ascertained  that  the  smell  and  taste 
of  brandy  from  corn  and  potato  are  owing 
to  a  peculiar  oil,  the  oil  of  potatoes.  This 
oil  is  more  closely  allied  to  alcohol  in  its 
properties,  than  to  any  other  organic  sub- 
stance. 

These  bodies  are  products  of  the  deoxida- 
tion  of  the  substances  dissolved  in  the  fer- 
menting liquids ;  they  contain  less  oxygen 
than  sugar  or  gluten,  but  are  remarkable  for 
the  large  quantity  of  hydrogen  which  enters 
into  their  composition. 

(Enanthic  acid  contains  an  equal  number 
of  equivalents  of  carbon  and  hydrogen, 
exactly  the  same  proportions  of  these  ele- 
ments, therefore,  as  sugar,  but  by  no  means 
the  same  proportion  of  oxygen.  The  oil  of 
potatoes  contains  much  more  hydrogen. 
Although  it  cannot  be  doubted  that  these 


VINOUS   FERMENTATION. 


105 


volatile  liquids  are  formed  by  a  mutual  in- 
terchange of  the  elements  of  gluten  and 
sugar,  in  consequence,  therefore,  of  a  true 
process  of  putrefaction,  still  it  is  certain,  that 
other  causes  exercise  an  influence  upon  their 
production  and  peculiarities. 

The  substances  in  wine  to  which  its  taste 
and  smell  are  owing,  are  generated  during 
the  fermentation  of  the  juice  of  such  grapes 
as  contain  a  certain  quantity  of  tartaric  acid ; 
they  are  not  found  in  wines  which  are  free 
from  all  acid,  or  which  contain  a  different 
organic  acid,  such  as  acetic  acid. 

The  wines  of  warm  climates  possess  no 
odour ;  wines  grown  in  France  have  it  in  a 
marked  degree,  but  in  the  wines  from  the 
Rhine  the  perfume  is  most  intense.  The 
kinds  of  grapes  on  the  Rhine,  which  ripen 
very  late,  and  scarcely  ever  completely,  such 
as  the  Riessling  and  Orleans,  have  the 
strongest  perfume  or  bouquet,  and  contain, 
proportionally,  a  larger  quantity  of  tartaric 
acid.  The  earlier  grapes,  such  as  the  Rw- 
lander,  and  others,  contain  a  large  propor- 
tion of  alcohol,  and  are  similar  to  Spanish 
wines  in  their  flavour,  but  they  possess  no 
bouquet. 

The  grapes  grown  at  the  Cape,  from 
Riesslings  transplanted  from  the  Rhine, 
produce  an  excellent  wine,  which  does  not, 
however,  possess  the  aroma  which  distin- 
guishes Rhenish  wine. 

It  is  evident  from  these  facts,  that  the  acid 
of  wines,  and  their  characteristic  perfumes, 
have  some  connexion,  for  they  are  always 
iound  together;  and  it  can  scarcely  be 
doubted  that  the  presence  of  the  former 
exercises  a  certain  influence  on  the  forma- 
tion of  the  latter.  This  influence  is  very 
plainly  observed  in  the  fermentation  of  li- 
quids, which  are  quite  free  from  tartaric 
acid,  and  particularly  of  those  which  are 
nearly  neutral  or  alkaline,  such  as  the  mash* 
of  potatoes  or  corn. 

The  brandy  obtained  from  corn  and  pota- 
toes contains  an  ethereal  oil  of  a  similar  com- 
position in  both,  to  which  these  liquors  owe 
their  peculiar  smell.  This  oil  is  generated 
during  the  fermentation  of  the  mash ;  it  exists 
ready  formed  in  the  fermented  liquids,  and 
distils  over  with  alcohol,  when  a  gentle  heat 
is  applied. 

It  is  observed  that  a  greater  quantity  of 
alcohol  is  obtained  when  the  mash  is  made 
quite  neutral  by  means  of  ashes  or  carbonate 
of  lime,  but  that  the  proportion  of  oil  in  the 
brandy  is  also  increased. 

Now  it  is  known  that  brandy  made  from 
potato  starch,  which  has  been  converted 
into  sugar  by  dilute  sulphuric  acid,  is  com- 
pletely free '  from  the  potato  oil,  so  that 
this  substance  must  be  generated  in  con- 
sequence of  a  change  suffered  by  the  cel- 
lular tissue  of  the  potatoes  during  their 
fermentation. 


*  Mash  is  the  mixture  of  malt,  potatoes,  and 
water,  in  the  mash  tun,  a  large  vessel  in  which  it 
te infused. 

14 


Experience  has  shown  that  the  simulta- 
neous fermentation  or  putrefaction  of  the 
cellular  tissue,  by  which  this  oil  is  generated, 
may  be  completely  prevented  in  the  fabrica- 
tion of  brandy  from  corn.* 

The  same  malt,  which  in  the  preparation 
of  brandy  yields  a  fluid  containing  the  oil  of 
which  we  are  speaking,  affords  in  the  for 
mation  of  beer  a  spirituous  liquor,  in  which 
no  trace  of  that  oil  can  be  detected.  The 
principal  difference  in  the  preparation  of  the 
two  liquids  is,  that  in  the  fermentation  of 
wort,  an  aromatic  substance  (hops)  is  added, 
and  it  is  certain  that  its  presence  modifies 
the  transformations  which  take  place.  Now 
it  is  known  that  the  volatile  oil  of  mustard, 
and  the  empyreumatic  oils,  arrest  completely 
the  action  of  yeast ;  and  although  the  oil  of 
hops  does  not  possess  this  property,  still  it 
diminishes,  in  a  great  degree,  the  influence 
of  decomposing  azotised  bodies  upon  the 
conversion  of  alcohol  into  acetic  acid.  There 
is,  therefore,  reason  to  believe  that  some 
aromatic  substances,  when  added  to  ferment- 
ing mixtures,  are  capable  of  producing  very 
various  modifications  in  the  nature  of  the 
producls  generated. 

Whatever  opinion,  however,  may  be  held 
regarding  the  origin  of  the  volatile  odorife- 
rous substances  obtained  in  the  fermentation 
of  wine,  it  is  quite  certain  that  the  charac- 
teristic smell  of  wine  is  owing  to  an  ether 
of  an  organic  acid,  resembling  one  of  the 
fatty  acids  (oenanthic  ether.) 

It  is  only  in  liquids  which  contain  other 
very  soluble  acids,  that  the  fatty  acids  and 
cenanthic  acids  are  capable  of  entering  into 
combination  with  the  ether  of  alcohol,  and 
of  thus  producing  compounds  of  a  peculiar 
smell.  This  ether  is  found  ..in  all  wines 
which  contain  free  acid,  and  is  absent  from 
those  in  which  no  acids  are  present.  This 
acid,  therefore,  is  the  means  by  which  the 
smell  is  produced;  since  without  its  presence 
cenanthic  ether  could  not  be  formed. 

The  greatest  part  of  the  oil  of  brandy 
made  from  corn  consists  of  a  fatty  acid  not 
converted  into  ether;  it  dissolves  oxide  of 
copper  and  metallic  oxides  in  general,  and 
combines  with  the  alkalies. 

The  principal  constituent  of  this  oil  is  an 
acid  identical  in  composition  with  cenanthic 
acid,  but  different  in  properties.  (Mulder.) 
It  is  formed  in  fermenting  liquids,  which,  if 
they  be  acid,  contain  only  acetic  acid,  a  body 
which  has  no  influence  in  causing  other 
acids  to  form  ethers. 

The  oil  of  brandy  made  from  potatoes  is 
the  hydrate  of  an  organic  base  analogous  to 
ether,  and  capable,  therefore,  of  entering  into 
combination  with  acids.  It  is  formed  in 
considerable  quantity  in  fermenting  liquids 
which  are  slightly  alkaline;  under  circum- 


*  In  the  manufactory  of  M.  Dubrunfaut,  so  con- 
siderable a  quantity  of  this  oil  is  obtained   under 
certain   circumstances  from  brandy  made  from 
potatoes,  that  it  might  be  employed  for  the  pur 
pose  of  illuminating  his  whole  manufactory. 


106 


AGRICLLTHRAL   CHEMI'STRY. 


stances,  consequently,  in  which  it  is  inca- 
pable of  combining  with  an  acid. 

The  products  of  the  fermentation  and 
putrefaction  of  neutral  vegetable  and  animal 
matters  are  generally  accompanied  by  sub- 
stances of  an  offensive  odour;  but  the  most 
remarkable  example  of  the  generation  of  a 
true  ethereal  oil  is  seen  in  the  fermentation 
of  the  Herba  centaurium  minorius,  a  plant 
which  possesses  no  smell.  When  it  is  ex- 
posed in  water  to  a  slightly  elevated  tempe- 
rature it  ferments,  and  emits  an  agreeable 
penetrating  odour.  By  the  distillation  of  the 
liquid,  an  ethereal  oily  substance  of  great 
volatility  is  obtained,  which  excites  a  prick- 
ing sensation  in  the  eyes,  and  a  flow  of 
tears.  (Biichner.) 

The  leaves  of  the  tobacco  plant  present 
the  same  phenomena;  when  fresh  they  pos- 
sess very  little  or  no  smell.  When  they  are 
subjected  to  distillation  with  water,  a  weak 
ammoniacal  liquid  is  obtained,  upon  which 
a  fatty  crystallizable  substance  swims,  which 
does  not  contain  nitrogen,  and  is  quite  desti- 
tute of  smell.  But  when  the  same  plant, 
after  being  dried,  is  moistened  with  water, 
tied  together  in  small  bundles,  and  placed 
in  heaps,  a  peculiar  process  of  decomposi- 
tion takes  place.  Fermentation  commences, 
and  is  accompanied  by  the  absorption  of 
oxygen ;  the  leaves  now  become  warm  and 
*<iiit  the  characteristic  smell  of  prepared  to- 
bacco and  snuff.  When  the  fermentation  is 
carefully  promoted  and  too  high  a  heat 
avoided,  this  smell  increases  and  becomes 
more  delicate;  and  after  the  fermentation  is 
completed,  an  oily  azotised  volatile  matter 
called  nicotine  is  found  in  the  leaves.  This 
substance — nicotine,  which  possesses  all  the 
properties  of^a  base,  was  not  present  before 
the  fermentation.  The  different  kinds  of 
tobacco  are  distinguished  from  one  another, 
like  wines,  by  having  very  different  odorife- 
rous substances,  which  are  generated  along 
with  the  nicotine. 

We  know  that  most  of  the  blossoms  and 
vegetable  substances  which  possess  a  smell 
owe  this  property  to  a  volatile  oil  existing 
in  them ;  but  it  is  not  less  certain,  that  others 
emit  a  smell  only  when  they  undergo  change 
or  decomposition. 

Arsenic  and  arsenious  acid  are  both  quite 
inodorous.  It  is  only  during  their  oxidation 
that  they  emit  their  characteristic  odour  of 
garlic.  The  oil  of  the  berries  of  the  elder- 
tree,  many  kinds  of  oil  of  turpentine,  and  oil 
of  lemons,  possess  a  smell  only  during  their 
oxidation  or  decay.  The  same  is  the  case 
with  many  blossoms;  and  Geiger  has  shown, 
that  the  smell  of  musk  is  owing  to  its  gradual 
putrefaction  and  decay. 

It  is  also  probable,  that  the  peculiar  odor- 
ous principle  of  many  vegetable  substances 
is  newly  formed  during  the  fermentation  of 
the  saccharine  juices  of  the  plants.  At  all 
events,  it  is  a  fact,  that  very  small  quantities 
of  the  blossoms  of  the  violet,  elder,  linden, 
or  cowslip,  added  to  a  fermenting  liquid,  are 
sufficient  to  communicate  a  very  strong  taste 


and  smell,  which  *he  addition  of  the  water 
distilled  from  a  quantity  a  hundred  times 
greater  would  not  effect.  The  various  kinds 
of  beer  manufactured  in  Bavaria  are  dis- 
tinguished by  different  flavours,  which  are 
given  by  allowing  small  quantities  of  the 
herbs  and  blossoms  of  particular  plants  to 
ferment  along  with  the  wort.  On  the  Rhine, 
also,  an  artificial  bouquet  is  often  given  to 
wine  for  fraudulent  purposes,  by  the  addition 
of  several  species  of  the  sage  and  rue  to  the 
fermenting  liquor;  but  the  fictitious  perfume 
thus  obtained  differs  from  the  genuine  aroma, 
by  its  inferior  durability,  and  by  being  gra- 
dually dissipated. 

The  juice  of  grapes  grown  in  different 
climates  differs  not  only  in  the  proportion 
of  free  acid  which  it  contains,  but  also  in 
respect  of  the  quantity  of  sugar  dissolved  in 
it.  The  quantity  of  azotised  matter  in  the 
juice  seems  to  be  the  same  in  whatever  part 
the  grapes  may  grow ;  at  least  no  difference 
has  been  observed  in  the  amount  of  yeast 
formed  during  fermentation  in  the  south  of 
France,  and  on  the  Rhine. 

The  grapes  grown  in  hot  climates,  as  well 
as  the  boiled  juice  obtained  from  them,  are 
proportionally  rich  in  sugar.  Hence,  during 
the  fermentation  of  the  juice,  the  complete 
decomposition  of  its  azotised  matters,  and 
their  separation  in  the  insoluble  state,  are 
effected  before  all  the  sugar  has  been  con- 
verted into  alcohol  and  carbonic  acid.  A 
certain  quantity  of  the  sugar  consequently 
remains  mixed  with  the  wine  in  an  unde- 
composed  state,  the  condition  necessary  for 
its  further  decomposition  being  absent. 

The  azotised  matters  in  the  juice  of  grapes 
of  the  temperate  zones,  on  the  contrary,  are 
not  completely  separated  in  the  insoluble 
state,  when  the  entire  transformation  of  the 
sugar  is  effected.  The  wine  of  these  grapes, 
therefore,  does  not  contain  sugar,  but  vari- 
able quantities  of  undecomposed  gluten  in 
solution. 

This  gluten  gives  the  wine  the  property 
of  becoming  spontaneously  converted  into 
vinegar,  when  the  access  of  air  is  not  pre- 
vented. For  it  absorbs  oxygen  and  becomes 
insoluble;  and  its  oxidation  is  communi- 
cated to  the  alcohol,  which  is  converted  into 
acetic  acid. 

By  allowing  the  wine  to  remain  at  rest  in 
casks  with  a  very  limited  access  of  air,  and 
at  the  lowest  possible  temperature,  the  oxida- 
tion of  this  azotised  matter  is  effected  with- 
out the  alcohol  undergoing  the  same  change, 
a  higher  temperature  being  necessary  to 
enable  alcohol  to  combine  with  oxygen.  As 
long  as  the  wine  in  the  stilling-casks  de- 
posits yeast,  it  can  still  be  caused  to  ferment 
by  the  addition  of  sugar,  but  old  well-layed 
wine  has  lost  this  property,  because  the  con- 
dition necessary  for  fermentation,  namely,  a 
substance  in  the  act  of  decomposition  or 
putrefaction,  is  no  longer  present  in  it. 

In  hotels  and  other  places  where  wine  is 
drawn  gradually  from  a  cask,  and  a  propor- 
tional quantity  of  air  necessarily  introduced, 


VINOUS   FERMENTATION. 


107 


us  ereraacausis,  that  is,  its  conversion  into 
acetic  acid,  is  prevented  by  the  addition  of  a 
small  quantity  of  sulphurous  acid.  This 
acid,  by  entering  into  combination  with  the 
oxygen  of  the  air  contained  in  the  cask,  or 
dissolved  in  the  wine,  prevents  the  oxidation 
of  the  organic  matter. 

The  various  kinds  of  beer  differ  from  one 
another  in  the  same  way  as  the  wines. 

English,  French,  and  most  of  the  German 
beers,  are  converted  into  vinegar  when  ex- 
posed to  the  action  of  air.  But  this  property 
is  not  possessed  by  Bavarian  beer,  which 
may  be  kept  in  vessels  only  half  filled  with- 
out acidifying  or  experiencing  any  change. 
This  valuable  quality  is  obtained  for  it  by  a 
peculiar  management  of  the  fermentation  of 
the  wort.  The  perfection  of  experimental 
knowledge  has  here  led  to  the  solution  of 
one  of  the  most  beautiful  problems  of  the 
theory  of  fermentation. 

Wort  is  proportionally  richer  in  gluten 
than  in  sugar,  so  that  during  its  fermenta- 
tion in  the  common  way,  a  great  quantity 
of  yeast  is  formed  as  a  thick  scum.  The 
carbonic  acid  evolved  during  the  process  at- 
taches itself  to  the  particles  of  the  yeast,  by 
which  they  become  specifically  lighter  than 
the  liquid  in  which  they  are  formed,  and  rise 
to  its  surface.  Gluten  in  the  act  of  oxida- 
tion comes  in  contact  with  the  particles  of 
the  decomposing  sugar  in  the  interior  of  the 
liquid.  The  carbonic  acid  from  the  sugar 
and  insoluble  ferment  from  the  gluten  are 
disengaged  simultaneously,  and  cohere  to- 
gether. 

A  great  quantity  of  gluten  remains  dis- 
solved in  the  fermented  liquid,  even  after  the 
transformation  of  the  sugar  is  completed, 
and  this  gluten  causes  the  conversion  of  the 
alcohol  into  acetic  acid,  on  account  of  its 
strong  disposition  to  attract  oxygen,  and  to 
undergo  decay.  Now,  it  is  plain,  that  with 
its  separation,  and  that  of  all  substances  ca- 
pable of  attracting  oxygen,  the  beer  would 
lose  the  property  of  becoming  acid.  This 
end  is  completely  attained  in  the  process  of 
fermentation  adopted  in  Bavaria. 

The  wort,  after  having  been  treated  with 
hops  in  the  usual  manner,  is  thrown  into 
very  wide  flat  vessels,  in  which  a  large  sur- 
face of  the  liquid  is  exposed  to  the  air. 
The  fermentation  is  then  allowed  to  proceed, 
while  the  temperature  of  the  chambers  in 
which  the  vessels  are  placed  is  never  allowed 
to  rise  above  45  to  50°  F.  The  fermentation 
lasts  from  three  to  six  weeks,  and  the  car- 
bonic acid  evolved  during  its  continuance  is 
not  in  large  bubbles  which  burst  upon  the 
surface  of  the  liquid,  but  in  small  bubbles 
like  those  which  escape  from  a  liquid  satu- 
rated by  high  pressure.  The  surface  of  the 
wort  is  scarcely  covered  with  a  scum,  and 
all  the  yeast  is  deposited  on  the  bottom  of 
the  vessel  in  the  form  of  a  viscous  sediment. 

In  order  to  obtain  a  clear  conception  of 
the  great  difference  between  the  two  kinds 
of  fermentation,  it  may  perhaps  be  sufficient 
to  recall  to  mind  the  fact,  that  the  transform- 


ation of  gluten  or  other  azotised  matters  is 
a  process  consisting  of  several  stages.  The 
first  stage  is  the  conversion  of  the  gluten 
into  insoluble  ferment  in  the  interior  of  the 
liquid,  and  as  the  transformation  of  the  su- 
gar goes  on  at  the  same  lime,  carooaic  acid 
and  yeast  are  simultaneously  disengaged. 
It  is  known  with  certainty,  that  mis  iorma~ 
tion  of  yeast  depends  upon  oxygen  being 
appropriated  by  the  gluten  in  the  act  of  de- 
composition ;  but  it  has  not  been  sufficiently 
shown  whether  this  oxygen  is  derived  from 
the  water,  sugar,  or  from  the  gluten  itself; 
whether  it  combines  directly  with  the  glu- 
ten, or  merely  with  its  hydrogen,  so  as  to 
form  water.  For  the  purpose  of  obtaining 
a  definite  idea  of  the  process,  we  may  de- 
signate the  first  change  as  the  stage  of  oxida- 
tion. This  oxidation  of  the  gluten  then, 
and  the  transposition  of  the  atoms  of  the 
sugar  into  alcohol  and  carbonic  acid,  are 
necessarily  attendant  on  each  other,  so  that 
if  the  one  is  arrested  the  other  must  also 
cease. 

Now,  the  yeast  which  rises  to  the  surface 
of  the  liquid  is  not  the  product  of  a  com- 
plete decomposition,  but  is  oxidised  gluten 
still  capable  of  undergoing  a  new  transform- 
ation by  the  transposition  of  its  constituent 
elements.  By  virtue  of  this  condition  it  has 
the  power  to  excite  fermentation  in  a  solu- 
tion of  sugar ;  and  if  the  gluten  be  also  pre- 
sent, the  decomposing  sugar  induces  its 
conversion  into  fresh  yeast,  so  that,  in  a  cer- 
tain sense,  the  yeast  appears  to  reproduce 
itself. 

Yeast  of  this  kind  is  oxidised  gluten  in  a 
state  of  putrefaction,  and  by  virtue  of  this 
state  it  induces  a  similar  transformation  in 
the  elements  of  the  sugar. 

The  yeast  formed  during  the  fermentation 
of  Bavarian  beer  is  oxidised  gluten  in  a  slate 
of  decay.  The  process  of  decomposition 
which  its  constituents  are  suffering,  gives 
rise  to  a  very  protracted  putrefaction  (/er- 
mentation)  in  the  sugar.  The  intensity  of 
the  action  is  diminished  in  so  great  a  degree, 
that  the  gluten  which  the  fluid  still  holds  in 
solution  takes  no  part  in  it ;  the  sugar  in 
fermentation  does  not  excite  a  similar  state 
in  the  gluten. 

But  the  contact  of  the  already  decaying 
and  precipitated  gluten  or  yeast  causes  the 
eremacausis  of  the  gluten  dissolved  in  the 
wort ;  oxygen  gas  is  absorbed  from  the  air, 
and  all  the  gluten  in  solution  is  deposited  as 
yeast. 

The  ordinary  frothy  yeast  may  be  removed 
from  fermenting  beer  by  filtration,  without 
the  fermentation  being  thereby  arrested ;  but 
precipitated  yeast  of  Bavarian  beer  cannot 
be  removed  without  the  whole  process  of  its 
fermentation  being  interrupted.  The  beer 
ceases  to  ferment  altogether,  or,  if  the  tem- 
perature is  raised,  undergoes  the  ordinary 
fermentation. 

The  precipitated  yeast  does  not  excite  or- 
dinary fermentation,  and  consequently  is 
quite  unfitted  for  the  purpose  of  baking ;  but 


108 


AGRICULTURAL    CHEMISTRY. 


tne  common  frothy  yeast  can  cause  the  kind 
of  fermentation  by  which  the  former  kind 
of  yeast  is  produced. 

When  common  yeast  is  added  to  wort  at 
a  temperature  of  be'tween  40°  and  45°  F.,  a 
slow  tranquil  fermentation  takes  place,  and 
a  matter  is  deposited  on  the  bottom  of  the 
vessel,  which  may  be  employed  to  excite 
new  fermentation ;  and  when  the  same  ope- 
ration is  repeated  several  times  in  succession, 
me  ordinary  fermentation  changes  into  that 
process  by  which  only  precipitated  yeast  is 
formed.  The  yeast  now  deposited  has  lost 
the  property  of  exciting  ordinary  fermenta- 
tion, but  it  produces  the  other  process  even 
at  a  temperature  of  50°  F. 

In  wort  subjected  to  fermentation,  at  a 
low  temperature,  with  this  kind  of  yeast, 
the  condition  necessary  for  the  transforma- 
tion of  the  sugar  is  the  presence  of  that 
yeast ;  but  for  the  conversion  of  gluten  into 
ferment  by  a  process  of  oxidation,  some- 
thing more  is  required. 

When  the  power  of  gluten  to  attract  oxy- 
gen is  increased  by  contact  with  precipitated 
yeast  in  a  state  of  decay,  the  unrestrained 
access  of  air  is  the  only  other  condition 
necessary  for  its  own  conversion  into  the 
same  state  of  decay,  that  is  for  its  oxidation. 
We  have  already  seen  that  the  presence  of 
free  oxygen  and  gluten  are  conditions  which 
determine  the  eremacausis  of  alcohol  and 
jts  conversion  into  acetic  acid,  but  they  are 
incapable  of  exerting  this  influence  at  low 
temperatures.  A  low  temperature  retards 
the  slow  combustion  of  alcohol,  while  the 
gluten  combines  spontaneously  with  the 
oxygen  of  the  air,  just  as  sulphuric  acid 
does  when  dissolved  in  water.  Alcohol  un- 
dergoes no  such  change  at  low  temperatures, 
but  during  the  oxidation  of  the  gluten  in 
contact  with  it,  is  placed  in  the  same  condi- 
tion as  the  gluten  itself  when  sulphurous 
acid  is  added  to  the  wine  in  which  it  is  con- 
tained. The  oxygen  of  the  air  unites  both 
with  the  gluten  and  alcohol  of  wine  not 
treated  with  sulphurous  acid  ;  but  when  this 
acid  is  present  it  combines  with  neither  of 
•  them,  being  altogether  absorbed  by  the  acid. 
The  same  thing  happens  in  the  peculiar  pro- 
cess of  fermentation  adopted  in  Bavaria.  The 
oxygen  of  the  air  unites  only  with  the  gluten 
and  not  with  the  alcohol,  although  it  would 
have  combined  with  both  at  higher  tempe- 
ratures, so  as  to  form  acetic  acid. 

Thus,  then,  this  remarkable  process  of 
fermentation  with  the  precipitation  of  a  mu- 
cous-like  ferment  consists  of  a  simultaneous 
putrefaction  and  decay  in  the  same  liquid. 
The.  sugar  is  in  the  state  of  putrefaction, 
and  the  gluten  in  that  of  decay. 

Appert's  method  of  preserving  food,  and 
this  kind  of  fermentation  of  beer,  depend  on 
the  same  principle. 

In  the  fermentation  of  beer  after  this  man- 
ner, all  the  substances  capable  of  decay  are 
separated  from  it  by  means  of  an  unre- 
strained access  of  air,  while  the  temperature 
is  kept  sufficiently  low  to  prevent  the  alco- 


hol from  combining  with  oxygen.  The  re 
moval  of  these  substances  diminishes  the 
tendency  of  the  beer  to  become  acescent,  or 
in  other  words.,  to  suffer  a  farther  transforma 
tion. 

In  Appert's  mode  of  preserving  food, 
oxygen  is  allowed  to  enter  into  combination 
with  the  substance  of  the  food,  at  a  tempe- 
rature at  which  decay,  but  neither  putrefac 
tion  nor  fermentation,  can  take  place.  With 
the  subsequent  exclusion  of  the  oxygen  and 
the  completion  of  the  decay,  every  cause 
which  could  effect  farther  decomposition  of 
the  food  is  removed.  The  conditions  for 
putrefaction  are  rendered  insufficient  in  both 
cases;  in  the  one  by  the  removal  of  the 
substances  susceptible  of  decay,  in  the  other 
by  the  exclusion  of  the  oxygen  which  would 
effect  it. 

It  has  been  stated  to  be  uncertain,  whether 
gluten  during  its  conversion  into  common 
yeast,  that  is,  into  the  insoluble  state  in 
which  it  separates  from  fermenting  liquids, 
really  combines  directly  with  oxygen.  If  it 
does  combine  with  oxygen,  then  the  difference 
between  gluten  and  ferment  would  be,  that 
the  latter  would  contain  a  larger  proportion 
of  oxygen.  Now  it  is  very  difficult  to  as- 
certain this,  and  even  their  analyses  cannot 
decide  the  question.  Let  us  consider,  for 
example,  the  relations  of  alloxan  and  allox- 
antin* to  one  another.  Both  of  these  bodies 
contain  the  same  elements  as  gluten,  although 
in  different  proportions.  Now  they  are  known 
to  be  convertible  into  each  other,  by  oxygen 
being  absorbed  in  the  one  case,  and  in  the 
other  extracted.  Both  are  composed  of  ab- 
solutely the  same  elements,  in  equal  pro- 
portions ;  with  the  single  exception,  that  al- 
loxantin contains  1  equivalent  of  hydrogen 
more  than  alloxan. 

When  alloxantin  is  treated  with  chlorine 
and  nitric  acid,  it  is  converted  into  alloxan, 
into  a  body,  therefore,  which  is  alloxantin 
minus  1  equivalent  of  hydrogen.  If  on  the 
other  hand  a  stream  of  sulphuretted  hydro- 
gen is  conducted  through  alloxan,  sulphur 
is  precipitated,  and  alloxantin  produced.  It 
may  be  said,  that  in  the  first  case  hydrogen 
is  abstracted,  in  the  other  added.  But  it 
would  be  quite  as  simple  an  explanation,  if 
we  considered  them  as  oxides  of  the  same 
radical :  the  alloxan  being  regarded  as  a 
combination  of  a  body  composed  of  C8  N« 
H«  O»  with  2  equivalents  of  water,  and  al- 
loxantin as  a  combination  of  3  atoms  of 
water,  with  a  compound  consisting  of  C* 
N«  H>  O*.  The  conversion  of  alloxan  into 
alloxantin  would  in  this  case  result  from  its 
eight  atoms  of  oxygen  being  reduced  to 
seven,  while  alloxan  would  be  formed  out 
of  alloxantin,  by  its  combining  with  an  ad- 
ditional atom  of  oxygen. 

Now,  oxides  are  known  which  combine 
with  water,  and  present  the  same  pheno- 
mena as  alloxan  and  alloxantin.  But  no 


*  Compounds  obtained  by  the  action  of  nitric 
acid  on  uric  acid. 


FERMENTATION   OF  BEER 


109 


compounds  of  hydrogen  are  known  which 
form  hydrates  ;  and  custom,  which  rejects 
all  dissimilarity  until  the  claim  to  peculiarity 
is  quite  proved,  leads  us  to  prefer  an  opinion, 
for  which  there  is  no  farther  foundation  than 
that  of  analogy.  The  woad  (Isatis  tinctoria) 
and  several  species  of  the  Nerium  contain  a 
substance  similar  in  many  respects  to  gluten, 
which  is  deposited  as  indigo  blue,  when  an 
aqueous  infusion  of  the  dried  leaves  is  ex- 
posed to  the  action  of  the  air.  Now  it  is 
very  doubtful  whether  the  blue  insoluble  in- 
digo is  an  oxide  of  the  colourless  soluble 
indigo,  or  the  latter  a  combination  of  hydro- 
gen with  the  indigo  blue.  Dumas  has  found 
the  same  elements  in  both,  except  that  the 
soluble  compound  contained  1  equivalent  of 
hydrogen  more  than  the  blue. 

In  the  same  manner  the  soluble  gluten 
may  be  considered  a  compound  of  hydrogen, 
which  becomes  ferment  by  losing  a  certain 
quantity  of  this  element  when  exposed  to 
the  action  of  the  oxygen  of  the  air  under  fa- 
vourable circumstances.  At  all  events,  it  is 
certain  that  oxygen  is  the  cause  of  the  in- 
soluble condition  of  gluten;  for  yeast  is  not 
deposited  on  keeping  wine,  or  during  the 
fermentation  of  Bavarian  beer,  unless  oxy- 
gen has  access  to  the  fluid. 

Now  whatever  be  the  form  in  which  the 
oxygen  unites  with  the  gluten — whether  it 
combines  directly  with  it  or  extracts  a  por- 
tion of  its  hydrogen,  forming  water — the 
products  formed  in  the  interior  of  the  liquid, 
in  consequence  of  the  conversion  of  the  glu- 
ten into  ferment,  will  still  be  the  same.  Let 
us  suppose  that  gluten  is  a  compound  of  an- 
other substance  with  hydrogen,  then  this 
hydrogen  must  be  removed  during  the  ordi- 
nary fermentation  of  must  and  wort,  by 
combining  with  oxygen,  exactly  as  in  the 
conversion  of  alcohol  into  aldehyd  by  ere- 
macausis. 

In  both  cases  the  atmosphere  is  excluded; 
the  oxygen  cannot,  then,  be  derived  from 
the  air,  neither  can  it  be  supplied  by  the 
elements  of  water,  for  it  is  impossible  to  sup- 
pose that  the  oxygen  will  separate  from  the 
hydrogen  of  water,  for  the  purpose  of  unit- 
ing with  the  hydrogen  of  gluten,  in  order 
again  to  form  water.  The  oxygen  must, 
therefore,  be  obtained  from  the  elements  of 
sugar,  a  portion  of  which  substance  must, 
hi  order  to  the  formation  of  ferment,  undergo 
a  different  decomposition  from  that  which 
produces  alcohol.  Hence  a  certain  part  of 
the  sugar  will  not  be  converted  into  carbonic 
acid  and  alcohol,  but  will  yield  other  pro- 
ducts containing  less  oxygen  than  sugar  it- 
self contains.  These  pfoducts,  as  has  already 
been  mentioned,  are  the  cause  of  the  great 
difference  in  the  qualities  of  fermented  li- 
quids, and  particularly  in  the  quantity  of 
alcohol  which  they  contain. 

Must  and  wort  do  not,  therefore,  in  ordi- 
nary fermentation,  yield  alcohol  in  propor- 
tion to  the  quantity  of  sugar  which  they 
hold  in  solut  m,  a  part  of  the  sugar  being 
employed  in  the  conversion  of  gluten  into  1 


ferment,  and  not  in  the  formation  of  alcohol. 
But  in  the  fermentation  of  Bavarian  beer  all 
the  sugar  is  expended  in  the  production  of 
alcohol;  and  this  is  especially  the  case  when- 
ever the  transformation  of  the  sugar  is  not 
accompanied  by  the  formation  of  yeast. 

It  is  quite  certain  that  in  the  distilleries  of 
brandy  from  potatoes,  where  no  yeast  is 
formed,  or  only  a  quantity  corresponding  to 
the  malt  which  has  been  added,  the  propor- 
tion of  alcohol  and  carbonic  acid  obtained 
during  the  fermentation  of  the  mash  corre- 
sponds exactly  to  that  of  the  carbon  contained 
in  the  starch.  It  is  also  known  that  the 
volume  of  carbonic  acid  evolved  during  the 
fermentation  of  beet-roots  gives  no  exact  in- 
dication of  the  proportion  of  sugar  contained 
in  them,  for  less  carbonic  acid  is  obtained 
than  the  same  quantity  of  pure  sugar  would 
yield. 

Beer  obtained  by  the  mode  of  fermenta- 
tion adopted  in  Bavaria  contains  more  alco- 
hol, and  possesses  more  intoxicating  proper- 
ties, than  that  made  by  the  ordinary  method 
of  fermentation,  when  the  quantities  of 
malt  used  are  the  same.  The  strong  taste 
of  the  former  beer  is  generally  ascribed  to  its 
containing  carbonic  acid  in  larger  quantity, 
and  in  a  state  of  more  intimate  combination  j 
but  this  opinion  is  erroneous.  Both  kinds 
of  beer  are,  at  the  conclusion  of  the  fermen- 
tation, completely  saturated  with  carbonic 
acid,  the  one  as  much  as  the  other.  Like 
all  other  liquids,  they  both  must  retain  such 
a  portion  of  the  carbonic  acid  evolved  as 
corresponds  to  their  power  of  solution,  that 
is,  to  their  volumes. 

The  temperature  of  the  fluid  during  fer 
mentation  has  a  very  important  influence 
on  the  quantity  of  alcohol  generated.  It 
has  been  mentioned,  that  the  juice  of  beet- 
roots allowed  to  ferment  at  from  86°  to  95° 
(30°  to  35°  C.)  yields  no  alcohol;  and  that 
afterwards,  in  the  place  of  the  sugar,  man- 
nite,  a  substance  incapable  of  fermentation, 
and  containing  very  little  oxygen,  is  found, 
together  with  lactic  acid  and  mucilage.  The 
formation  of  these  product?  diminishes  in 
proportion  as  the  temperature  is  lower.  But 
in  vegetable  juices,  containing  nitrogen,  it  is 
impossible  to  fix  a  limit,  where  the  trans- 
formation of  the  sugar  is  undisturbed  by 
any  other  process  of  decomposition. 

It  is  known  that  in  the  fermentation  of 
Bavarian  beer  the  action  of  the  oxygen  of 
the  air,  and  the  low  temperature,  cause 
complete  transformation  of  the  sugar  into 
alcohol ;  the  cause  which  would  prevent  that 
result,  namely,  the  extraction  of  the  oxygen 
of  part  of  the  sugar  by  the  gluten,  in  its 
conversion  into  ferment,  being  avoided  by 
the  introduction  of  oxygen  from  without. 

The  quantity  of  matters  in  the  act  of 
transformation  is  naturally  greatest  at  the 
beginning  of  the  fermentation  of  must  and 
wort;  and  all  the  phenomena  which  accom- 
pany the  process,  such  as  evolution  of  gas, 
and  heat,  are  best  observed  at  that  time. 
These  signs  of  the  changes  proceeding  in 


no 


AGRICULTURAL  CHEMISTRY. 


the  fluiu  diminish  when  the  greater  part  of 
the  sugar  has  undergone  decomposition; 
but  they  must  cease  entirely  before  the  pro- 
rets  can  be  regarded  as  completed. 

The  less  rapid  process  of  decomposition 
which  succeeds  the  violent  evolution  of  gas, 
continues  in  wine  and  beer  until  the  sugar 
has  completely  disappeared ;  and  hence  it  is 
observed,  that  the  specific  gravity  of  the 
liquid  diminishes  during  many  months. 
This  slow  fermentation,  in  most  cases,  re- 
sembles the  fermentation  of  Bavarian  beer, 
the  transformation  of  the  dissolved  sugar 
being  in  part  the  result  of  a  slow  and  con- 
tinued decomposition  of  the  precipitated 
yeast;  but  a  complete  separation  of  the 
azotised  substances  dissolved  in  it  cannot 
take  place  when  air  is  excluded.* 

Neither  alcohol  alone,  nor  hops,  nor  in- 
deed both  together,  preserve  beer  from  be- 
coming acid.  The  better  kinds  of  ale  and 
porter  in  England  are  protected  from  acidity, 
but  at  the  loss  of  the  interest  of  an  immense 
capital.  They  are  placed  in  large  closed 
wooden  vessels,  the  surfaces  of  which  are 
covered  with  sand.  In  these  they  are  al- 
lowed to  lie  for  several  years,  so  that  they 
are  treated  in  a  manner  exactly  similar  to 
wine  during  its  ripening. 

A  gentle  diffusion  of  air  takes  place 
through  the  pores  of  the  wood,  but  the  quan- 
tity of  azotised  substances  being  very  great 
in  proportion  to  the  oxygen  which  enters, 
they  consume  it,  and  prevent  its  union  with 
the  alcohol.  But  the  beer  treated  in  this 
way  does  not  keep  for  two  months  without 
acidifying,  if  it  be  placed  in  smaller  vessels, 
to  which  free  access  of  the  air  is  permitted. 


CHAPTER  X. 

DECAY    OF   WOODY    FIBRE. 

THE  conversion  of  woody  fibre  into  the 
substances  termed  humus  and  mould  is,  on 
account  of  its  influence  on  vegetation,  one 
of  the  most  remarkable  processes  of  decom- 
position which  occur  in  nature. 

Decay  is  not  less  important  in  another 
point  of  view ;  for,  by  means  of  its  influ- 
ence on  dead  vegetable  matter,  the  oxygen 
fchich  plants  retained  during  life  is  again 
restored  to  the  atmosphere. 

The  decomposition  of  woody  fibre  is  ef- 
fected in  three  forms,  the  results  of  which 

*  The  great  influence  which  a  rational  manage- 
ment of  fermentation  exercises  upon  the  quality 
of  beer  is  well  known  in  several  of  the  German 
states.  In  the  grand-duchy  of  Hesse,  for  example, 
a  considerable  premium  is  offered  for  the  prepa- 
ration of  beer,  according  to  the  Bavarian  method  ; 
and  the  premium  is  to  be  adjudged  to  any  one 
who  can  prove  that  the  beer  brewed  by  him  has 
lain  for  six  months  in  the  store-vats  without  be- 
coming acid.  Hundreds  of  casks  of  beer  became 
changed  to  vinegar  before  an  empirical  knowledge 
of  those  conditions  was  obtained,  the  influence  of 
which  is  rendered  intelligible  by  the  theory. 


are  different,  so  that  it  is  necessary  to  con- 
sider each  separately. 

The  first  lakes  place  when  it  is  in  the 
moist  condition,  and  subject  to  free  uninter- 
rupted access  of  air;  the  second  occurs 
when  the  air  is  excluded;  and  the  third 
when  the  wood  is  covered  with  water,  and 
in  contact  with  putrefying  organic  matter. 

It  is  known  that  woody  fibre  may  be  kept 
under  water,  or  in  dry  air,  for  thousands  of 
years  without  suffering  any  appreciable 
change;  but  that  when  brought  into  contact 
with  air,  in  the  moist  condition,  it  converts  the 
oxygen  surrounding  it  into  the  same  volume 
of  carbonic  acid,  and  is  itself  gradually 
changed  into  a  yellowish  brown,  or  black 
matter,  of  a  loose  texture.* 

It  has  already  been  mentioned,  that  pure 
woody  fibre  contains  carbon  and  the  ele- 
ments of  water.  Humus,  however,  is  not 
produced  by  the  decay  of  pure  woody  fibre, 
but  by  that  of  wood  which  contains  foreign 
soluble  and  insoluble  organic  substances, 
besides  its  essential  constituents. 

The  relative  proportion  of  the  component 
elements  are,  on  this  account,  different  in 
oak  wood  and  in  beech,  and  the  composition 
of  both  of  these  differs  very  much  from 
woody  fibre,  which  is  the  same  in  all  vege- 
tables. The  difference,  however,  is  so  tri- 
vial, that  it  may  be  altogether  neglected  in 
the  consideration  of  the  questions  which 
will  now  be  brought  under  discussion ;  be- 
sides, the  quantity  of  the  foreign  substances 
is  not  constant,  but  varies  according  to  the 
season  of  the  year. 

According  to  the  careful  analysis  of  Gay- 
Lussac  and  Thenard,  100  parts  of  oak  wood, 
dried  at  212°  (100°  C.,)  from  which  all 
soluble  substances  had  been  extracted  by 
means  of  water  and  alcohol,  contained 
52-53  parts  of  carbon,  and  47-47  parts  of 
hydrogen  and  oxygen,  in  the  same  propor- 
tion as  they  are  contained  in  water. 

Now  it  has  been  mentioned  that  moist 
wood  acts  in  oxygen  gas  exactly  as  if  its 
carbon  combined  directly  with  oxygen,  and 
that  the  products  of  this  action  are  carbonic 
acid  and  humus. 

If  the  action  of  the  oxygen  were  confined 
to  the  carbon  of  the  wood,  and  if  nothing 
but  carbon  were  removed  from  it,  the  re- 
maining elements  would  necessarily  be 
found  in  the  humus,  unchanged  except  in 
the  particular  of  being  combined  with  less 
carbon.  The  final  result  of  the  action  would 
therefore  be  a  complete  disappearance  of  the 
carbon,  whilst  nothing  but  the  elements  of 
water  would  remain. 

But  when  decaying  wood  is  subjected  to 
examination  in  different  stages  of  its  decay, 


*  According  to  the  experiments  of  DC  Saussure, 
240  parts  of  dry  sawdust  of  oak  wood  convert  10 
cubic  inches  of  oxygen  into  the  same  quantity  of 
carbonic  acid,  which  contains  3  parts,  by  weight, 
of  carbon  ;  while  the  weight  of  the  sawdust  is  di- 
minished by  15  parts.  Hence,  12  parts,  by  weight, 
of  water,  are  at  the  same  time  separated  from  the 
elements  of  the  wood. 


DECAY   OF   WOODY   FIBRE. 


Ill 


the  remarkable  result  is  obtained,  that  the  j 
proportion  of  carbon  in  the  different  products  j 
augments.     Consequently,  if  we   did   not  ] 
take  into  consideration  the  evolution  of  car- 
bonic acid  under  the  influence  of  the  air, 
the  conversion  of  wood  into  humus  might ' 
be  viewed  as  a  removal  of  the  elements  of 
water  from  the  carbon. 

The   analysis  of   mouldered  oak  wood, 
which  was  taken  from  the   interior  of  the  I 
trunk  of  an  oak,  and  possessed  a  chocolate  ! 
brown  colour  and  the  structure   of  wood,  I 
showed  that  100  parts  of  it  contained  53" 36 
parts  of  carbon  and  46*44  parts  of  hydrogen 
and  oxygen  in  the  same  relative  proportions 
as   in    water.      From   an   examination  of 
mouldered  wood  of  a  light  brown  colour, 
easily  reducible  to  a  fine  powder,  and  taken 
from  another  oak,  it  appeared  that  it  con- 
tained 56-21 1  carbon  and  43789  water. 

These  indisputable  facts  point  out  the 
similarity  of  the  decay  of  wood  with  the 
slow  combustion  or  oxidation  of  bodies 
which  contain  a  large  quantity  of  hydrogen. 
Viewed  as  a  kind  of  combustion,  it  would 
indeed  be  a  very  extraordinary  process,  if 
the  carbon  combined  directly  with  the  oxy- 
gen ;  for  it  would  be  a  combustion  in  which 
the  carbon  of  the  burning  body  augmented 
constantly,  instead  of  diminishing.  Hence 
it  is  evident  that  it  is  the  hydrogen  which  is 
oxidised  at  the  expense  of  the  oxygen  of  the 
air ;  wnile  the  carbonic  acid  is  formed  from 
the  elements  of  the  wood.  Carbon  never 
combines  at  common  temperatures  with 
oxygen,  so  as  to  form  carbonic  acid. 

In  whatever  stage  of  decay  wood  may  be, 
its  elements  must  always  be  capable  of  be- 
ing represented  by  their  equivalent  numbers. 

The  following  formula  illustrates  this  fact 
with  great  clearness : 

C36  H22  O22— oak  wood,  according  to  Gay- 
Lussac  and  Thenard.* 

C35  H20  O20— humus  from  oak  wood  (Meyer.)t 
C34  HIS  0 18— humus  from   oak  wood  (Dr. 

Will.)* 

It  is  evident  from  these  numbers  that  for 
every  two  equivalents  of  hydrogen  which 
are  oxidised,  two  atoms  of  oxygen  and  cne 
of  carbon  are  set  free. 

Under  ordinary  circumstances,  woody 
fibre  requires  a  very  long  time  for  its  decay  ; 
but  this  process  is  of  course  much  accele- 
rated by  an  elevated  temperature  and  free  un- 
restrained access  of  air.  The  decay,  on  the 
contrary,  is  much  retarded  by  absence  of 
moisture,  and  by  the  wood  being  surrounded 
with  an  atmosphere  of  carbonic  acid,  which 
prevents  the  access  of  air  to  the  decaying 
matters. 

Sulphurous  acid,  and  all  antiseptic  sub- 
stances, arrest  the  decay  of  woody  fibre.  It 


*  The  calculation  gives  52'5  carbon,  and  47'5 
water. 

t  The  calculation  gives  54  carbon,  and  46 
water. 

t  Tlv.  Calculation  gives  56  carbon,  and  44 
water. 


is  well  known  that  corrosive  sublimate  is 
employed  for  the  purpose  of  protecting  the 
timber  of  ships  from  decay;  it  is  a  substance 
which  completely  deprives  vegetable  or  ani- 
mal matters,  the  most  prone  to  decomposi- 
tion, of  their  property  of  entering  into  fer- 
mentation, putrefaction,  or  decay. 

But  the  decay  of  woody  fibre  is  very 
much  accelerated  by  contact  with  alkalies  or 
alkaline  earths;  for  these  enable  substances 
to  absorb  oxygen,  which  do  not  possess 
this  power  themselves;  alcohol,  gallic  acid, 
tannin,  the  vegetable  colouring  matters,  and 
several  other  substances,  are  thus  affected 
by  them.  Acids  produce  quite  an  opposite 
effect;  they  greatly  retard  decay. 

Heavy  soils,  consisting  of  loam,  retain 
longest  the  most  important  condition  for  the 
decay  of  the  vegetable  matter  contained  in 
them,  viz.,  water;  but  their  impermeable 
nature  prevents  contact  with  the  air. 

In  moist  sandy  soils,  particularly  such  as 
are  composed  of  a  mixture  of  sand  and  car- 
bonate of  lime,  decay  proceeds  very  quickly, 
it  being  aided  by  the  presence  of  the  slightly 
alkaline  lime. 

Now  let  us  consider  the  decay  of  woody 
fibre  during  a  very  long  period  of  lime,  and 
suppose  that  its  cause  is  the  gradual  removal 
of  the  hydrogen  in  the  form  of  water,  and 
the  separation  of  its  oxygen  in  that  of  car- 
bonic acid.  It  is  evident  that  if  we  sub-" 
tract  from  the  formula  C36,  H22,  O22,  the  22 
equivalents  of  oxygen,  with  11  equivalents 
of  carbon,  and  22  equivalents  of  hydrogen, 
which  are  supposed  to  be  oxidised  by  *he 
oxygen  of  the  air,  and  separated  in  the  form 
of  water;  then  from  1  atom  of  oak  wood, 
25  atoms  of  pure  carbon  will  remain  as  the 
final  product  of  the  decay.  In  other  words, 
100  parts  of  oak,  which  contain  52'5  parts 
of  carbon,  will  leave  as  a  residue  37  parts 
of  carbon,  which  must  remain  unchanged, 
since  carbon  does  not  combine  with  oxygen 
at  common  temperatures. 

But  this  final  result  is  never  attained  in 
the  decay  of  wood  under  common  circum- 
stances ;  and  for  this  reason,  that  with  the 
increase  of  the  proportion  of  carbon  in  the 
residual  humus,  as  in  all  decompositions  of 
this  kind,  its  attraction  for  the  hydrogen, 
which  still  remains  in  combination,  also  in- 
creases, until  at  length  the  affinity  of  oxygen 
for  the  hydrogen  is  equalled  by  that  of  the 
carbon  for  the  same  element. 

In  proportion  as  the  decay  of  woody  fibre 
advances,  its  property  of  burning  with  flame, 
or  in  other  words,  of  developing  carburetted 
hvdrogen  on  the  application  of  heat,  dimi- 
nishes. Decayed  wood  burns  without  flame; 
whence  no  other  conclusion  can  be  drawn, 
than  that  the  hydrogen,  which  analysis 
shows  to  be  present,  is  not  contained  in  it 
in  the  same  form  as  in  wood. 

Decayed  oak  contains  more  carbon  than 
fresh  wood,  but  its  hydrogen  and  oxygen 
are  in  the  same  proportion. 

We  would  naturally  expect  that  the  flame 
given  out  by  decayed  wood  should  be  more 


AGRICULTUU^  ^    CHEMISTRY. 


orilhant,  in  proportion  to  the  increase  of  its 
carbon,  but  we  find,  on  the  contrary,  that  it 
burns  like  tinder,  exactly  as  if  no  hydrogen 
were  present.  For  the  purposes  of  fuel, 
decayed  or  diseased  wood  is  of  little  value, 
for  it  does  not  possess  the  property  of  burn- 
ing with  flame,  a  property  upon  which  the 
advantages  of  common  wood  depend.  The 
hydrogen  of  decayed  wood  must  conse- 
quently be  supposed  to  be  in  the  state  of 
water;  for  had  it  any  other  form,  the  charac- 
ters we  have  described  would  not  be  pos- 
sessed by  the  decayed  wood. 

If  we  suppose  decay  to  proceed  in  a  liquid, 
which  contains  both  carbon  and  hydrogen, 
then  a  compound  containing  still  more  car- 
bon must  be  formed,  in  a  manner  similar  to 
the  production  of  the  crystalline  colourless 
naphthalin  from  a  gaseous  compound  of 
carbon  and  hydrogen.  And  if  the  compound 
thus  formed  were  itself  to  undergo  further 
decay,  the  final  result  must  be  the  separation 
of  carbon  in  a  crystalline  form. 

Science  can  point  to  no  process  capable 
of  accounting  for  the  origin  and  formation 
of  diamonds,  except  the  process  of  decay. 
Diamonds  cannot  be  produced  by  the  action 
of  fire,  for  a  high  temperature,  and  the  pre- 
sence of  oxygen  gas,  would  call  into  play 
their  combustibility.  But  there  is  the  greatest 
reason  to  believe  that  they  are  formed  in  the 
humid  way,  that  is,  in  a  liquid,  and  the  pro- 
cess of  decay  is  the  only  cause  to  which  their 
formation  can  with  probability  be  ascribed. 

Amber,  fossil  resin,  and  the  acids  in  mel- 
lite,  are  the  products  of  vegetable  matter 
which  has  suffered  decomposition.  They 
are  found  in  wood  or  brown  coal,  and  have 
evidently  proceeded  from  the  decomposition 
of  substances  which  were  contained  in  quite 
a  different  form  in  the  living  plants-.  They 
are  all  distinguished  by  the  proportionally 
small  quantity  of  hydrogen  which  they  con- 
tain. The  acid  from  mellite  (mellitic  acid) 
contains  precisely  the  same  proportions  of 
carbon  and  oxygen  as  that  from  amber  (suc- 
cinic  acid ;)  they  differ  only  in  the  propor- 
tion of  their  hydrogen.  M.  Bromeis*  found 
that  succinic  acid  might  be  artificially  formed 
by  the  action  of  nitric  acid  on  stearic  acid,  a 
true  process  of  eremacausis;  the  experiment 
was  made  in  this  laboratory  (Giessen.) 

CHAPTER  XL 

VEGETABLE    MOULD. 

THE  term  vegetable  mould,  in  its  general 
signification,  is  applied  to  a  mixture  of  dis- 
integrated minerals,  with  the  remains  of 
animal  and  vegetable  substp'ices.  It  may 
be  considered  as  earth  in  which  humus  is 
contained  in  a  state  of  decomposition.  Its 
action  upon  the  air  has  been  fully  investi- 
gated by  Ingenhouss  and  De  Saussure. 

When  moist  vegetable  mould  is  placed  in 
a  vessel  full  of  air,  it  extracts  the  oxygen 

*  Lie-big's  Annalen,  Band  xxxiv.,  Heft  3.. 


therefrom  with  greater  rapidity  than  decayed 
wood,  and  replaces  it  by  an  equal  volume  of 
carbonic  acid.  When  this  carbonic  acid  is 
removed  and  fresh  air  admitted,  the  same 
action  is  repeated. 

Cold  water  dissolves  only  1(y^00th  of  its 
own  weight  of  vegetable  mould;  and  the 
residue  left  on  its  evaporation  consists  of 
common  salt  with  traces  of  sulphate  of  pot- 
ash and  lime,  and  a  minute  quantity  of  "or- 
ganic matter,  for  it  is  blackened  when  heated 
to  redness.  Boiling  water  extracts  several 
substances  from  vegetable  mould,  and  ac- 
quires a  yellow  or  yellowish  brown  colour, 
which  is  dissipated  by  absorption  of  oxygen 
from  the  air,  a  black  flocculent  deposit  being 
formed.  When  the  coloured  solution  is 
evaporated,  a  residue  is  left  which  becomes 
black  on  being  heated  to  redness,  and  after- 
wards yields  carbonate  of  potash  when 
treated  with  water. 

A  solution  of  caustic  potash  becomes 
black  when  placed  in  contact  with  vegetable 
mould,  and  the  addition  of  acetic  acid  to  the 
coloured  solution  causes  no  precipitate  or 
turbidity.  But  dilute  sulphuric  acid  throws 
down  a  light  flocculent  precipitate  of  a 
brown  or  black  colour,  from  which  the  acid 
can  be  removed  wit  difficulty  by  means  of 
water.  When  this  precipitate,  after  having 
been  washed  with  water,  is  brought  whilst 
still  moist  under  a  receiver  filled  with  oxy- 
gen, the  gas  is  absorbed  with  great  rapidity  ; 
and  the  same  thing  takes  place  when  the 
precipitate  is  dried  in  the  air.  In  the  per- 
fectly dry  state  it  has  entnely  lost  its  solu- 
bility in  water,  and  even  alkalies  dissolve 
only  traces  of  it. 

It  is  evident,  therefore,  that  boiling  water 
extracts  a  matter  from  vegetable  mould, 
which  owes  its  solubility  to  the  presence  of 
the  alkaline  salts  contained  in  the  remains 
of  plants.  This  substance  is  a  product  01 
the  incomplete  decay  of  woody  fibre.  Its 
composition  is  intermediate  between  woody 
fibre  and  humus,  into  which  it  is  converted, 
by  being  exposed  in  a  moist  condition  to 
the  action  of  vhe  air. 


CHAPTER  XII. 

ON    THE     MOULDERING    OF    BODIES. PAPER, 

BROWN    COAL,  AND    MINERAL    COAL. 

THE  decomposition  of  wood,  woody  fibre, 
and  all  vegetable  bodies  when  subjected  to 
the  action  of  water,  and  excluded  from  the 
air,  is  termed  mouldering. 

Wood,  or  brown  coal  and  mineral  coal, 
are  the  remains  of  vegetables  of  a  former 
world;  their  appearance  and  characters 
show,  that  they  are  products  of  the  pro- 
cesses of  decomposition  termed  decay  and 
putrefaction.  We  can  easily  ascertain  by 
analysis  the  manner  in  whicn  their  consti- 
tuents have  been  changed,  if  we  suppose 
the  greater  part  of  their  bulk  to  have  been 
formed  from  woody  fibre, 
i  But  it  is  necessary,  before  we  can  obtain 


MOULDERING    OF    BODIES. 


113 


a  distinct  idea  of  the  manner  in  which  coal 
is  formed,  to  consider  a  peculiar  change 
which  woody  fibre  suffers  by  means  of 
moisture,  when  partially  or  entirely  ex- 
cluded from  the  air. 

It  is'  known,  that  when  pure  woody  fibre, 
as  linen,  for  example,  is  placed  in  contact 
with  water,  considerable  heat  is  evolved, 
and  the  substance  is  converted  into  a  soft 
friable  mass  which  has  lost  all  coherence. 
This  substance  was  employed  in  the  fabri- 
cation of  paper  before  the  use  of  chlorine,  as 
an  agent  for  bleaching.  The  rags  employed 
for  this  purpose  were  placed  in  heaps,  and 
it  was  observed,  that  on  their  becoming 
warm  a  gas  was  disengaged,  and  their 
weight  diminished  from  18  to  25  per  cent. 

When  sawdust  moistened  with  water  is 
placed  in  a  closed  vessel,  carbonic  acid  gas 
is  evolved  in  the  same  manner  as  when  air 
is  admitted.  A  true  putrefaction  takes  place, 
the  wood  assumes  a  white  colour,  loses  its 
peculiar  texture,  and  is  converted  into  a  rot- 
ten friable  matter. 

The  white  decayed  wood  found  in  the  in- 
terior of  trunks  of  dead  trees  which  have 
been  in  contact  with  water,  is  produced  in 
the  way  just  mentioned. 

An  analysis  of  wood  of  this  kind,  ob- 
tained from  the  interior  of  the  trunk  of  an 
oak,  yielded,  after  having  been  dried  at  212°, 

Carbon 
Hydrogen 
Oxygen 
Ashes 


47-11 
6-31 

45-31 
1-27 

lOO'OO 


48-14 
6-06 

44-43 
137 

100-00 


Now,  on  comparing  the  proportions  ob- 
tained from  these  numbers  with  the  compo- 
sition of  oak  wood,  according  to  the  analysis 
of  Gay-Lussac  and  Thenard,  it  is  imme- 
diately perceived,  that  a  certain  quantity  of 
carbon  has  been  separated  from  the  consti- 
tuents of  wood,  whilst  the  hydrogen  is,  on 
the  contrary,  increased.  The  numbers  ob- 
tained by  the  analysis  correspond  very  nearly 
to  the  formula  C33  H27  O24.* 

The  elements  of  water  have,  therefore, 
become  united  with  the  wood,  whilst  car- 
bonic acid  is  disengaged  by  the  absorption 
of  a  certain  quantity  of  oxygen. 

If  the  elements  of  5  atoms  of  water  and  3 
atoms  of  oxygen  be  added  to  the  composi- 
tion of  the  woody  fibre  of  the  oak,  and  3 
atoms  of  carbonic  acid  deducted,  the  exact 
formula  for  white  mouldered  wood  is  ob- 
tained. 


Wood 

To  this  add  5  atoms  of  water 

3  atoms  of  oxygen 


C36  H22  O22 

H  5  O  5 

O  3 


C36  H27  O30 

Subtract  from  this  3  atoms  car- 
bonic acid  -  -  C  3  O  6 


C33  H27  O24 


The  process  of  mouldering  is,  therefore 
one  of  putrefaction  and  decay,  proceeding 
simultaneously,  in  which  the  oxygen  of  the 
air  and  the  component  parts  of  water  take 
part.  But  the  composition  of  mouldered 
wood  must  change  according  as  the  access 
of  oxygen  is  more  or  less  prevented.  White 
mouldered  beech-wood  yielded  on  analysis 
47'67  carbon,  5-67  hydrogen,  and  46'(>8 
oxygen;  this  corresponds  to  the  formula 
C33  H25  O24. 

The  decomposition  of  wood  assumes, 
therefore,  two  different  forms,  according  as 
the  access  of  the  air  is  free  or  restrained. 
In  both  cases  carbonic  acid  is  generated; 
and  in  the  latter  case,  a  certain  quantity  of 
water  enters  into  chemical  combination. 

It  is  highly  probable  that  in  this  putrefac- 
tive process,  as  well  as  in  all  others,  the 
oxygen  of  the  water  assists  in  the  formation 
of  the  carbonic  acid. 

Wood  coal  (brown  coal  of  Werner)  must 
have  been  produced  by  a  process  of  decom- 
position similar  to  that  of  mouldering.  But 
it  is  not  easy  to  obtain  wood  coal  suited  for 
analysis,  for  it  is  generally  impregnated  with 
resinous  or  earthy  substances,  by  which  the 
composition  of  those  parts  which  have  been 
formed  from  woody  fibre  is  essentially 
changed. 

The  wood  coal,  which  forms  extensive 
layers  in  the  Wetterau  (a  district  in  Hesse 
Darmstadt,)  is  distinguished  from  that  found 
in  other  places,  by  possessing  the  structure 
of  wood  unchanged,  and  by  containing  ao 
bituminous  matter.  This  coal  was  subjected 
to  analysis,  a  piece  being  selected  upon 
which  the  annual  circle  could  be  counted. 
It  was  obtained  from  the  vicinity  of  Lau- 
bach;  100  parts  contained 

Carbon  ....  57'28 

Hydrogen  -            •           -            -  6 '03 

Oxygen     -  •'.',..            .            .  26'10 

Ashes  -            -            •            •  0'59 

100-00 

The  large  amount  of  carbon,  and  small 
quantity  of  oxygen,  constitute  the  most  ob- 
vious difference  between  this  analysis  and 
that  of  wood.  It  is  evident  that  the  wood 
which  has  undergone  the  change  into  coal 
must  have  parted  with  a  certain  portion  of 
its  oxygen.  The  proportions  of  these  num 
bers  are  expressed  by  the  formula  C33  H21 
016.* 

When  these  numbers  are  compared  with 
those  obtained  by  the  analysis  of  oak,  it 
would  appear  that  the  brown  coal  was  pro- 
duced from  woody  fibre  by  the  separation: 
of  one  equivalent  of  hydrogen,  and  the  ele- 
ments of  three  equivalents  of  carbonic  acid. 

1  atom  wood  -  C36  H22  022 

Minus  1  atom  hydrogen  and  3?  r1  a  TT  i   n  c 
atoms  carbonic  acil  -  J  C81 

Wood  coal,       C33  H21  O16 


*  The  calculation  from  this  formula  jrives  in  100        *  The  calculation  gives  57'5  carbon,  and  5'98 
parts  47'9  carbon,  6'1  hydrogen,  and  46  oxygen.    ;  hydrogen. 


15 


114 


AGRICULTURAL   CHEMISTRY. 


All  varieties  of  wood  coal,  from  whatever 
Btrata  they  may  be  taken,  contain  more  hy- 
drogen than  wood  does,  and  less  oxygen 
than  is  necessary  to  form  water  with  this 
hydrogen;  consequently  they  must  all  be 
produced  by  the  same  process  of  decompo- 
sition. The  excess  of  hydrogen  is  either 
hydrogen  of  the  wood  which  has  remained 
ill  it  unchanged,  or  it  is  derived  from  some 
exterior  source.  The  analysis  of  wood  coal 
from  Ringkuhl,  near  Cassel,  where  it  is 
seldom  found  in  pieces  with  the  structure  of 
wood,  gave,  when  dried  at  212°, 


Carbon 

Hydrogen 

Oxygen 

Ashes 


62-60 

5-02 

26-52 

5-86 


6383 
4-80 

25-51 
5-86 

100-00 


100-00 

The  proportions  derived  from  these  num- 
bers correspond  very  closely  to  the  formula 
C32  H15  O9,  or  they  represent  the  constitu- 
ents of  wood,  from  which  the  elements  of 
carbonic  acid,  water,  and  2  equivalents  hy- 
drogen, have  been  separated. 

C36H22  O2>2+Wood. 

Subtract  C  4  H  7  O13-(- 4  atoms  carbonic  acid-^- 

5  atoms  of  water 

2  atoms  of  hydrogen. 

C32  H15  O  9=  Wood  Coal  from  Ring- 
kuhl. 


The  formation  of  both  these  specimens  of 
wood  coal  appears  from  these  formulae  to 
have  taken  place  under  circumstances  which 
did  not  entirely  exclude  the  action  of  the  air, 
and  consequent  oxidation  and  removal  of  a 
certain  quantity  of  hydrogen.  Now  the 
Laubacher  coal  is  covered  with  a  layer  of 
basalt,  and  the  coal  of  Ringkuhl  was  taken 
from  the  lowest  seam  of  layers,  which  pos- 
sess a  thickness  of  from  90  to  120  feet;  so 
that  both  may  be  considered  as  well  protected 
from  the  air. 

During  the  formation  of  brown  coal,  the 
elements  of  carbonic  acid  have  been  sepa- 
rated from  the  wood  either  alone,  or  at  the 
same  time  with  a  certain  quantity  of  water. 
It  is  quite  possible  that  the  difference  in  the 
process  of  decomposition  may  depend  upon 
the  high  temperature  and  pressure  under 
which  the  decomposition  took  place.  At 
least,  a  piece  of  wood  assumed  the  character 
and  appearace  of  Laubacher  coal,  after  be- 
ing kept  for  several  weeks  in  the  boiler  of  a 
steam  engine,  and  had  then  precisely  the 
same  composition.  The  change  in  this  case 
was  effected  in  water,  at  a  temperature  of 
from  3340  to  3520  p.  (150°— 160°  C.,)  and 
under  a  corresponding  pressure.  The  ashes 
of  the  wood  amounted  to  0-51  per  cent. ;  a 
little  less,  therefore,  than  those  of  the  Lau- 
hacher  coal ;  but  this  must  be  ascribed  to 
the  peculiar  circumstances  under  which  it 
was  formed.  The  ashes  of  plants  examined 
by  Bemier  amounted  always  to  much  more 
than  this. 

The  peculiar  process  by  which  the  de- 
composition of  these  extiait  vegetables  has 


been  effected,  namely,  a  disengagement  of 
carbonic  acid  from  their  substance,  appears 
still  to  go  on  at  great  depths  in  all  the  layers 
of  wood  coal.  At  all  events  it  is  remarkable 
that  springs  impregnated  with  carbonic  acid 
occur  in  many  places,  in  the  country  be- 
tween Meissner,  in  the  electorate  of  Hesse, 
and  the  Eifel,  which  are  known  to  possess 
large  layers  of  wood  coal.  These  springs 
of  mineral  water  are  produced  on  the  spot 
at  which  they  are  found  ;  the  springs  of 
common  water  meeting  with  carbonic  acid 
during  their  ascent,  and  becoming  impreg- 
nated with  it. 

In  the  vicinity  of  the  layers  of  wood  coal 
at  Salshausen  (Hesse  Darmstadt)  an  excel- 
lent acidulous  spring  of  this  kind  existed  a 
few  years  ago,  and  supplied  all  the  inhabi- 
tants of  that  district;  but  it  was  considered 
advantageous  to  surround  the  sides  «f  the 
spring  with  sandstone,  and  the  consequence 
was,  that  all  the  outlets  to  the  carbonic  acid 
were  closed,  for  this  gas  generally  gains  ac- 
cess to  the  water  from  the  sides  of  the 
spring.  From  that  time  to  the  present  this 
valuable  mineral  water  has  disappeared,  and 
in  its  place  is  found  a  spring  of  common 
water. 

Springs  of  water  impregnated  with  car- 
bonic acid  occur  at  Schwalheim,  at  a  very 
short  distance  from  the  layers  of  wood  coal 
at  Dorheim.  M.  Wilhelmi  observed  some 
time  since,  that  they  are  formed  of  commoa 
spring  water  which  ascends  from  below, 
and  of  carbonic  acid  which  issues  from  the 
sides  of  the  spring.  This  same  fact  has 
been  shown  to  be  the  case  in  the  famed 
Fachinger  spring,  by  M.  Schapper. 

The  carbonic  acid  gas  from  the  springs  in 
the  Eifel  is,  according  to  BischofF,  seldom 
|  mixed  with  nitrogen  or  oxygen,  and  is  pro- 
bably produced  in  a  manner  similar  to  that 
just  described.  At  any  rate  the  air  does 
not  appear  to  take  any  part  in  the  formation 
of  these  acidulous  springs.  The  carbonic 
acid  has  evidently  not  been  formed  either  by 
a  combustion  at  high  or  low  temperatures ; 
for  if  it  were  so,  the  gas  resulting  from  the 
combustion  would  necessarily  be  mixed  with 
£  of  nitrogen,  but  it  does  not  contain  a  trace 
of  this  element.  The  bubbles  of  gas  which 
escape  from  these  springs  are  absorbed  by 
caustic  potash,  with  the  exception  of  a  resi- 
duum too  small  to  be  appreciated. 

The  wood  coal  of  Dorheim  and  Salzhau- 
sen  must  have  been  formed  in  the  same  way 
as  that  of  the  neighbouring  village  of  Lau- 
bach  ;  and  since  the  latter  contains  the  exact 
elements  of  woody  fibre,  minus  a  certain 
quantity  of  carbonic  acid,  its  composition 
indicates  very  plainly  the  manner  in  which 
j  it  has  been  produced. 

The  coal  of  the  upper  bed  is  subjected  to 
an  incessant  decay  by  the  action  of  the  air, 
by  means  of  which  its  hydrogen  is  removed 
in  the  same  manner  as  in  the  decay  of  wood. 
This  is  recognised  by  the  way  in  which  it 
burns,  and  by  the  formation  of  carbonic  arid 
in  the  mines. 


POISONS,   CONTAGIONS,   MIASMS. 


The  gases  which  are  formed  in  mines  of 
wood  coal,  and  cause  danger  in  their  work- 
ing, are  not  combustible  or  inflammable  as 
in  mines  of  mineral  coal ;  but  they  consist 
generally  of  carbonic  acid  gas,  and  are  very 
seldom  intermixed  with  combustible  gases. 

Wood  coal  from  the  middle  bed  of  the 
strata  at  Ringkuhl  gave  on  analysis  65-40 — 
64-01  carbon  and  4-75 — 4'76*  hydrogen ;  the 
proportion  of  carbon  here  is  the  same  as  in 
specimens  procured  from  greater  depths,  but 
that  of  the  hydrogen  is  much  less. 

Wood  and  mineral  coal  are  always  ac- 
companied by  iron  pyrites  (sulphuret  of 
iron)  or  zinc  blende  (sulphuret  of  zinc ;) 
which  minerals  are  still  formed  from  salts 
of  sulphuric  acid,  with  iron  or  zinc,  during 
the  putrefaction  of  all  vegetable  matter.  It 
is  possible  that  the  oxygen  of  the  sulphates 
in  the  layers  of  wood  coal  is  the  means  by 
which  the  removal  of  the  hydrogen  is 
effected,  since  wood  coal  contains  less  of 
this  element  than  wood. 

According  to  the  analysis  of  Richardson 
and  Regnault,  the  composition  of  the  com- 
bustible materials  in  splint  coal  from  New- 
castle, and  can n el  coal  from  Lancashire, 
is  expressed  by  the  formula  C24  HI 3  O. 
When  this  is  compared  with  the  composition 
of  woody  fibre,  it  appears  lhat  these  coals 
are  formed  from  its  elements,  by  the  re- 
moval of  a  certain  quantity  of  carburetted 
hydrogen  and  carbonic  acid  in  the  form  of 
combustible  oils.  The  composition  of  both 
of  these  coals  is  obtained  by  the  subtraction 
of  3  atoms  of  carburetted  hydrogen,  3  atoms 
of  water,  and  9  atoms  of  carbonic  acid  from 
the  formula  of  wood. 


3  atoms  of  carburet- 
ted hydrogen  C3  H6 

3  atoms  of  water    H3    O3 

9  atoms  of  carbonic 
acid  -  -  C9  O18 


Mineral  coal 


C36  H22  022=wood 


C12  H  9  O21 


C24  H13  O 


Carburetted  hydrogen  generally  accom- 
panies all  mineral  coal ;  other  varieties  of 
coal  contain  volatile  oils  which  may  be  sepa- 
rated by  distillation  with  water.  (Reichen- 
bach.)  The  origin  of  naphtha  is  owing  to 
a  similar  process  of  decomposition.  Caking 
coal  from  Caresfield,  near  Newcastle,  con- 
tains the  elements  of  cannel  coal,  minus  the 
constituents  of  olefiant  gas  C4  H4. 

The  inflammable  gases  which  stream  out 
of  clefts  in  the  strata  of  mineral  coal,  or  in 
rocks  of  the  coal  formations,  always  con- 
tain carbonic  acid,  according  to  a  recent 
examination  by  Bischoff,  and  also  carburet- 
ted hydrogen,  nitrogen,  and  olefiant  gas; 
the  last  of  which  had  not  been  observed, 
until  its  existence  in  these  gases  was  pointed 
out  by  Bischoff.  The  analysis  of  fire-damp 


*  The  analysis  of  brown  coal  from  Ringkuhl, 
as  well  as  all  those  of  the  same  substance  given 
in  this  work,  have  been  executed  in  this  labora- 
tory by  M.  Kiihnert  of  Cassel. 


after  it  had  been  treated  with  caustic  potash 
showed  its  constituents  to  be, 

Gas  from  an. 

abandoned  Gerhard's  Gas  from  9 

mine  near  passage  near  mine  near 

Wallesweiler.  Luisenthal.  Lickwfge. 

Vol.  Vol.  Vol. 
Light  carburetted 

hydrogen      91'36  83.08  7910 

Olefiant  gas        6'32  1'98  16' 11 

Nitrogen  gas      2'32  14'94             4"79 

100-00       100-00       100-00 

The  evolution  of  these  gases  proves  that 
changes  are  constantly  proceeding  in  the 
coal. 

It  is  obvious  from  this,  that  a  continual 
removal  of  oxygen  in  the  form  of  carbonic 
acid  is  effected  from  layers  of  wood  coal,  in 
consequence  of  which  the  wood  must  ap- 
proach gradually  to  the  composition  of 
mineral  coal.  Hydrogen,  on  the  contrary,  is 
disengaged  from  the  constituents  of  mineral 
coal  in  the  form  of  a  compound  of  carbo-hy- 
drogen;  a  complete  removal  of  all  the  hydro- 
gen would  convert  coal  into  anthracite. 

The  formula  C36  H22  O22,  which  is 
given  for  wood,  has  been  chosen  as  the  em- 
pirical expression  of  the  analysis,  for  the 
purpose' of  bringing  all  the  transformations 
which  woody  fibre  is  capable  of  undergoing 
under  one  common  point  of  view. 

Now,  although  the  correctness  of  this 
formula  must  be  doubted,  until  we  know 
with  certainty  the  true  constitution  of  woody 
fibre,  this  cannot  have  the  smallest  influence 
on  the  account  given  of  the  changes  to  which 
woody  fibre  must  necessarily  be  subjected  in 
order  to  be  converted  into  wood  or  mineral 
coal.  The  theoretical  expression  refers  to 
the  quantity,  the  empirical  merely  to  the 
relative  proportion  in  which  the  elements  of 
a  body  are  united.  Whatever  form  the  first 
may  assume,  the  empirical  expression  must 
always  remain  unchanged. 


CHAPTER  XIII. 

ON  POISONS,  CONTAGIONS,  AND  MIASMS. 

A  GREAT  many  chemical  compounds, 
some  derived  from  inorganic  nature,  and 
others  formed  in  animals  and  plants,  pro- 
duce peculiar  changes  or  diseases  in  the 
living  animal  organism.  They  destroy  the 
vital  functions  of  individual  organs;  and 
when  their  action  attains  a  certain  degree 
of  intensity,  death  is  the  consequence. 

The  action  of  inorganic  compounds,  such 
as  acids,  alkalies,  metallic  oxides,  and  salts, 
can  in  most  cases  be  easily  explained.  They 
either  destroy  the  continuity  of  particular 
organs,  or  they  enter  into  combination  with 
their  substance.  The  action  of  sulphuric, 
muriatic,  and  oxalic  acids,  hydrate  of  pot- 
ash, and  all  those  substances  which  produce 
the  direct  destruction  of  the  organs  with 
which  they  come  into  contact,  may  be  com- 
I  >ared  to  a  piece  of  iron,  which  can  caus* 


116 


AGRICULTURAL   CHEMISTRY. 


death  by  inflicting  an  injury  on  particular  |      During  the  passage  of  these  salts  through 
organs,  either  when  heated  to   redness,  or   the  lungs,  their  acids  take  part  in  the  pecn- 


when  in  the  form  of  a  sharp  knife.  Such 
substances  are  not  poisons  in  the  limited 
sense  of  the  word,  for  their  injurious  action 
depends  merely  upon  their  condition. 

The  action  of  the  proper  inorganic  poisons 
is  owing,  in  most  cases,  to  the  formation  of 
a  chemical  compound  by  the  union  of  the 
poison  with  the  constituents  of  the  organ 
upon  which  it  acts;  it  is  owing  to  an  exer- 
cise of  a  chemical  affinity  more  powerful 
lhan  the  vitality  of  the  organ. 

It  is  well  to  consider  the  action  of  inor- 
ganic substances  in  general,  in  order  to  ob- 
tain a  clear  conception  of  the  mode  of  action 
of  those  which  are  poisonous.  We  find 
that  certain  soluble  compounds,  when  pre- 
sented to  different  parts  of  the  body,  are  ab- 
sorbed by  the  blood,  whence  they  are  again 
eliminated  by  the  organs  of  secretion,  either 
in  a  changed  or  in  an  unchanged  state. 

Iodide  of  potassium,  sulpho-cyanuret  of 
potassium,  ferro-cyanuret  of  potassium, 
chlorate  of  potash,  silicate  of  potash,  and  all 
salts  with  alkaline  bases,  when  administered 
internally  to  man  and  animals  in  dilute  solu- 
tions, or  applied  externally,  may  be  again 
detected  in  the  blood,  sweat,  chyle,  gall,  and 
splenic  veins ;  but  all  of  them  are  finally  ex- 
creted from  the  body  through  the  urinary 
passages. 

Each  of  these  substances,  in  its  transit, 
produces  a  peculiar  disturbance  in  the  or- 
ganism— in  other  words,  they  exercise  a 
medicinal  action  upon  it,  but  they  them- 
selves suffer  no  decomposition.  If  any  of 
these  substances  enter  into  combination  with 
any  part  of  the  body,  the  union  cannot  be 
of  a  permanent  kind;  for  their  reappearance 
in  the  urine  shows  that  any  compounds 
thus  formed  must  have  been  again  decom- 
posed by  the  vital  processes. 

Neutral  citrates,  acetates,  and  tartrates  of 
the  alkalies,  suffer  change  in  their  passage 
through  the  organism.  Their  bases  can 
indeed  be  detected  in  the  urine,  but  the  acids 
have  entirely  disappeared,  and  are  replaced 
by  carbonic  acid  which  has  united  with  the 
bases.  (Gilbert  Blane  and  Wohler.) 

The  conversion  of  these  salts  of  organic 
acids  into  carbonates,  indicates  that  a  con- 
siderable qantity  of  oxygen  must  have  united 
with  their  elements.  In  order  to  convert  1 
equivalent  of  acetate  of  potash  into  the  car- 
bonate of  the  same  base,  8  equivalents  of 
oxygen  must  combine  with  it,  of  which 
either  2  or  4  equivalents  (according  as  an 
acid  or  neutral  salt  is  produced)  remain  in 
combination  with  the  alkali;  whilst  the  re- 
maining 6  or  4  equivalents  are  disengaged 
as  free  carbonic  acid.  There  is  no  evidence 
presented  by  the  organism  itself,  to  which 
these  salts  have  been  administered,  that  any 
of  its  proper  constituents  have  yielded  so 
great  a  quantity  of  oxygen  as  is  necessary 
for  their  conversion  into  carbonates.  Their 
oxidation  can,  therefore,  only  be  ascribed 
to  the  oxygen  of  the  air. 


liar  process  of  eremacausis  which  proceeds 
in  that  organ ;  a  certain  quantity  of  the  oxy- 
gen gas  inspired  unites  with  their  constitu- 
ents, and  converts  their  hydrogen  into  water, 
and  their  carbon  into  carbonic  acid.  Part 
of  this  latter  product  (1  or  2  equivalents) 
remains  in  combination  with  the  alkaline 
base,  forming  a  salt  which  suffers  no  farther 
change  by  the  process  of  oxidation ;  and  it 
is  this  salt  which  is  separated  by  the  kidneys 
or  liver. 

It  is  manifest  that  the  presence  of  these 
organic  salts  in  the  blood  must  produce  a 
change  in  the  process  of  respiration.  A  part 
of  the  oxygen  inspired,  which  usually  com- 
bines with  the  constituents  of  the  blood, 
must,  when  they  are  present,  combine  with 
their  acids,  and  thus  be  prevented  from  per- 
forming its  usual  office.  The  immediate 
consequence  of  this  must  be  the  formation 
of  arterial  blood  in  less  quantity,  or  in  other 
words,  the  process  of  respiration  must  be 
retarded. 

Neutral  acetates,  tartrates,  and  citrates 
placed  in  contact  with  the  air,  and  at  the 
same  time  with  animal  or  vegetable  bodies 
in  a  state  of  eremacausis,  produce  exactly 
the  same  effects  as  we  have  described  them 
to  produce  in  the  lungs.,  They  participate 
in  the  process  of  decay,  and  are  converted 
into  carbonates  just  as  in  the  living  body. 
If  impure  solutions  of  these  salts  in  water 
are  left  exposed  to  the  air  for  any  length  of 
time,  their  acids  are  gradually  decomposed," 
and  at  length  entirely  disappear. 

Free  mineral  acids,  or  organic  acids  which 
are  not  volatile,  and  salts  of  mineral  acids 
with  alkaline  bases,  completely  arrest  decay 
when  added  to  decaying  matter  in  sufficient 
quantity ;  and  when  their  quantity  is  small, 
the  process  of  decay  is  protracted  and  re- 
tarded. They  produce  in  living  bodies  the 
same  phenomena  as  the  neutral  organic 


salts,  but  their  action  depends  upon  a  differ- 
ent cause. 

The  absorption  by  the  blood  of  a  quantity 
of  an  inorganic  salt  sufficient  to  arrest  the 
process  of  eremacausis  in  the  lungs,  is  pre- 
vented by  a  very  remarkable  property  of  all 
animal  membranes,  skin,  cellular  tissue, 
muscular  fibre,  &c. ;  namely,  by  their  inca- 
pability of  being  permeated  by  concentrated 
saline  solutions.  It  is  only  when  these  so- 
lutions are  diluted  to  a  certain  degree  with 
water  that  they  are  absorbed  by  animal 
tissues. 

A  dry  bladder  remains  more  or  less  dry 
in  saturated  solutions  of  common  salt,  nitre, 
ferro-cyanuret  of  potassium,  sulpho-cyanu- 
ret of  potassium,  sulphate  of  magnesia, 
chloride  of  potassium,  and  sulphate  of  soda. 
These  solutions  run  off  its  surface  in  the 
same  manner  as  water  runs  from  a  plate  of 
glass  besmeared  with  tallow. 

Fresh  flesh,  over  which  salt  has  been 
strewed,  is  found  after  24  hours'  swimming 
in  brine,  although  not  a  drop  of  water  has 


POISONS,    CONTAGIONS,    MIASMS. 


117 


been  idded.  The  water  has  been  yielded 
bv  muscular  fibre  itself,  and  having  dis- 
solved the  sa  .t  in  immediate  contact  with  it, 
and  thereby  lost  the  power  of  penetrating 
animal  substances,  it  has  on  this  account 
separated  from  the  flesh.  The  water  still 
retained  by  the  flesh  contains  a  proportion- 
ally small  quantity  of  salt,  having  that  de- 
gree of  dilution  at  which  a  saline  fluid  is 
capable  of  penetrating  animal  substances. 

This  property  of  animal  tissues  is  taken 
advantage  of  in  domestic  economy  for  the 
purpose  of  removing  so  much  water  from 
meat  that  a  sufficient  quantity  is  not  left  to 
enable  it  to  enter  into  putrefaction. 

In  respect  of  this  physical  property  of 
animal  tissues,  alcohol  resembles  the  inor- 
ganic salts.  It  is  incapable  of  moistening, 
that  is,  of  penetrating,  animal  tissues,  and 
possesses  such  an  affinity  for  water  as  to 
extract  it  from  moist  substances. 

When  a  solution  of  a  salt,  in  a  certain  de- 
gree of  dilution,  is  introduced  into  the  sto- 
mach, it  is  absorbed ;  but  a  concentrated 
saline  solution,  in  place  of  being  itself  ab- 
sorbed, extracts  water  from  the  organ,  and 
a  violent  thirst  ensues.  Some  interchange 
of  water  and  salt  takes  place  in  the  stomach ; 
the  coats  of  this  viscus  yield  water  to  the 
solution,  a  part  of  which  having  previously 
become  sufficiently  diluted,  is,  on  the  other 
hand,  absorbed.  But  the  greater  part  of  the 
concentrated  solution  of  salt  remains  unab- 
sorbed,  and  is  not  removed  by  the  urinary 
passages;  it  consequently  enters  the  intes- 
tines and  intestinal  canal,  where  it  causes  a 
dilution  of  the  solid  substances  deposited 
there,  and  thus  acts  as  a  purgative. 

Each  of  the  salts  just  mentioned  pos- 
sesses this  purgative  action,  which  depends 
on  a  physical  property  shared  by  all  of 
them  ;  but  besides  this  they  exercise  a  me- 
dicinal action,  because  every  part  of  the 
organism  with  which  they  cqme  in  contact 
absorbs  a  certain  quantity  of  them. 

The  composition  of  the  salts  has  nothing 
to  do  with  their  purgative  action  ;  it  is  quite 
a  matter  of  indifference  a"  far  as  the  mere 
production  of  this  action  is  concerned  (not 
as  to  its  intensity,)  whether  the  base  be 
potash  or  soda,  or  in  many  cases  lime  and 
magnesia ;  and  whether  the  acid  be  phos- 
phoric, sulphuric,  nitric,  or  hydrochloric. 

Besides  these  salts,  the  action  of  which 
does  not  depend  upon  their  power  of  enter- 
in?  into  combination  with  the  component ; 
Darts  of  the  organism,  there  is  a  large  class 
of  others  which,  when  introduced  into  the 
living  body,  effect  changes  of  a  very  differ- 
ent kind,  and  produce  diseases  or  death,  ac- 
cording to  the  nature  of  these  changes,  with- 
out effecting  a  visible  lesion  of  any  organs. 

These  are  the  true  inorganic  poisons,  the 
action  of  which  depends  upon  their  power 
of  forming  permanent  compounds  with  the 
substance  of  the  membranes,  and  muscular  ! 
fibre. 

Salts  of  lead,  iron  bismuth,  copper,  and 
mercury,  belong  to  this  class. 


When  solutions  of  these  salts  are  treated 
with  a  sufficient  quantity  of  albumen,  milk, 
muscular  fibre,  and  animal  membranes,  they 
enter  into  combination  with  those  sub- 
stances, and  lose  their  own  solubility  ;  while 
the  water  in  which  they  were  dissolved  loses 
all  the  salt  which  it  contained. 

The  salts  of  alkaline  bases  extract  water 
from  animal  substances ;  whilst  the  salts  of 
the  heavy  metallic  oxides  are,  on  the  con- 
trary, extracted  from  the  water,  for  they 
enter  into  combination  with  the  animal 
matters. 

Now,  when  these  substances  are  adminis- 
tered to  an  animal,  they  lose  their  solubility 
by  entering  into  combination  with  the  mem- 
branes, cellular  tissue,  and  muscular  fibre; 
but  in  very  few  cases  can  they  reach  the 
blood.  All  experiments  instituted  for  the 
purpose  of  determining  whether  they  pass 
into  the  urine  have  failed  to  detect  them  in 
that  secretion.  In  fact,  during  their  pas- 
sage through  the  organism,  they  come  into 
contact  with  many  substances  by  which 
they  are  retained. 

The  action  of  corrosive  sublimate  and 
arsenious  acid  is  very  remarkable  in  this 
respect.  It  is  known  that  these  substances 
possess,  in  an  eminent  degree,  the  property 
of  entering  into  combination  with  all  parts 
of  animal  and  vegetable  bodies,  rendering 
them  at  the  same  time  insusceptible  of  decay 
or  putrefaction.  Wood  and  cerebral  sub- 
stance are  both  bodies  whicn  undergo  change 
with  great  rapidity  and  facility  when  sub- 
ject to  the  influence  of  air  and  water ;  but 
if  they  are  digested  for  some  time  with  ar- 
senious acid  or  corrosive  sublimate,  they 
may  subsequently  be  exposed  to  all  the  in- 
fluences of  the  atmosphere  without  altering 
in  colour  or  appearance. 

It  is  farther  known  that  those  parts  of  a 
body  which  come  in  contact  with  these  sub- 
stances during  poisoning,  and  which  there- 
fore enter  into  combination  with  them,  do 
not  afterwards  putrefy;  so  that  there  can  be 
no  doubt  regarding  the  cause  of  their  poi- 
sonous qualities. 

It  is  obvious  that  if  arsenious  acid  and 
corrosive  sublimate  are  not  prevented  by  the 
vital  principle  from  entering  into  combina- 
tion with  the  component  parts  of  the  body, 
and  consequently  from  rendering  them  inca- 
pable of  decay  and  putrefaction,  they  must 
deprive  the  organs  of  the  principal  property 
which  appertains  to  their  vital  condition, 
viz.  that  of  suffering  and  effecting  trans- 
formations ;  or,  in  other  words,  organic  life 
must  be  destroyed.  If  the  poisoning  is 
merely  superficial,  and  the  quantity  of  the 
poison  so  small  that  only  individual  parts 
of  the  body  which  are  capable  of  being  re- 
generated have  entered  into  combination 
with  it,  then  eschars  are  produced — a  phe- 
nomenon of  a  secondary  kind — the  com- 
pounds of  the  dead  tissues  with  the  poison 
being  thrown  off  by  the  healthy  parts. 
From  these  considerations  it  may  readily  be 
inferred  that  all  internal  signs  of  poisoning 


118 


AGRICULTURAL   CHEMISTRY. 


are  variable  and  uncertain ;  for  cases  may 
happen,  in  which  no  apparent  indication  of 
change  can  be  detected  by  simple  observa- 
tions of  the  parts,  because,  as  has  been  al- 
ready remarked,  death  may  occur  without 
the  destruction  of  any  organs. 

When  arsenious  acid  is  administered  in 
solution,  it  may  enter  into  the  blood.  If  a 
vein  is  exposed  and  surrounded  with  a  solu- 
tion of  this  acid,  every  blood-globule  will 
combine  with  it,  that  is,  will  become  poi- 
soned. 

The  compounds  of  arsenic,  which  have 
not  the  property  of  entering  into  combina- 
tion witn  the  tissues  of  the  organism,  are 
without  influence  on  life,  even  in  large  doses. 
Many  insoluble  basic  salts  of  arsenious  acid 
are  known  not  to  be  poisonous.  The  sub- 
stance called  alkargeri,  discovered  by  Bunsen, 
has  not  the  slightest  injurious  action  upon 
the  organism ;  yet  it  contains  a  very  large 
quantity  of  arsenic,  and  approaches  very 
2-losely  in  composition  to  the  organic  arse- 
nic :.s  compounds  found  in  the  body. 

These  considerations  enable  us  to  fix  with 
tolerable  certainty  the  limit  at  which  the 
above  substances  cease  to  act  as  poisons. 
For  since  their  combination  with  organic 
matters  must  be  regulated  by  chemical  laws, 
death  will  inevitably  result,  when  the  organ 
in  contact  with  the  poison  finds  sufficient 
of  it  to  unite  with  atom  for  atom ;  whilst  if 
the  poison  is  present  in  smaller  quantity,  a 
part  of  the  organ  will  retain  its  vital  func- 
tions. 

According  to  the  experiments  of  Mulder,* 
the  equivalent  in  which  fibrin  combines  with 
muriatic  acid,  and  with  the  oxides  of  lead 
and  copper,  is  expressed  by  the  number  6361. 
It  may  be  assumed  therefore  approxima- 
tively,  that  a  quantity  of  fibrin  correspond- 
ing to  the  number  '6361  combines  with  1 
equivalent  of  arsenious  acid,  or  1  equiva- 
lent of  corrosive  sublimate. 

When  6361  parts  of  anhydrous  tinrm  are 
combined  with  30,000  parts  of  waier,  it  is 
in  the  state  in  which  it  is  contained  in  mus- 
cular fibre  or  blood  in  the  human  body. 
100  £,  Ams  of  fibrin  in  this  condition  would 
form  a  neutral  compound  of  equal  equiva- 
lents with  3T^  grains  of  arsenious  acid,  and 
5  grains  of  corrosive  sublimate. 

The  atomic  weight  of  the  albumen  of 
eggs  and  of  the  blood  deduced  from  the 
analysis  of  the  compound  which  it  forms 
with  oxide  of  silver  is  7447,  and  that  of 
animal  gelatin  5652. 

100  grains  of  albumen  containing  all  the 
water  with  which  it  is  combined  in  the  liv- 
ing body,  should  consequently  combine  with 
l£  grain  of  arsenious  acid. 

These  proportions  which  may  be  consi- 
dered as  the  highest  which  can  be  adopted, 
indicate  the  remarkably  high  atomic  weights 
of  animal  substances,  and  at  the  same  time 
teach  us  what  very  small  quantities  of  arse- 


*  Poggendorff's  Annalen,  Band  xl.  S.  259. 


mous  acid  or  corrosive  sublimate  are  requi- 
site to  produce  deadly  effects. 

All  substances  administered  as  antidotes 
in  cases  of  poisoning,  act  by  destroying  die 
power  which  arsenious  acid  and  corrosive 
sublimate  possess,  of  entering  into  combi- 
nation with  animal  matters,  and  of  thus 
acting  as  poisons.  Unfortunately  no  other 
body  surpasses  them  in  that  power,  and  the 
compounds  which  they  form  can  only  be 
broken  up  by  affinities  so  energetic,  tha 
their  action  is  as  injurious  as  that  of  the 
above-named  poisons  themselves.  The  duty 
of  the  physician  consists,  therefore,  in  his 
causing  those  parts  of  the  poison  which 
may  be  free  and  still  uncombined,  to  enter 
into  combination  with  some  other  body,  so 
as  to  produce  a  compound  incapable  of 
being  decomposed  or  digested  in  the  same 
conditions.  Hydrated  peroxide  of  iron  is 
an  invaluable  substance  for  this  purpose. 

When  the  action  of  arsenious  acid  or 
corrosive  sublimate  is  confined  to  the  sur- 
face of  an  organ,  those  parts  only  are  de- 
stroyed which  enter  into  combination  with 
it;  an  eschar  is  formed,  which  is  gradually 
thrown  off. 

Soluble  salts  of  silver  would  be  quite  as 
deadly  a  poison  as  corrosive  sublimate,  did 
not  a  cause  exist  in  the  human  body  by 
which  their  action  is  prevented,  unless  their 
quantity  is  very  great.  This  cause  is  the 

Eresence  of  common  salt  in  all  animal 
quids.  Nitrate  of  silver,  it  is  well  known, 
combines  with  animal  substances,  in  the 
same  manner  as  corrosive  sublimate,  and 
the  compounds  formed  by  both  are  exactly 
similar  in  the  character  of  being  incapable 
of  decay  or  putrefaction. 

When  nitrate  of  silver  in  a  state  of  solu- 
tion is  applied  to  skin  or  muscular  fibre,  it 
combines  with  them  instantaneously;  ani- 
mal substances  dissolved  in  any  liquid  are 
precipitated  by  it,  and  rendered  insoluble, 
or,  as  it  is  usually  termed,  they  are  coagu- 
lated. The  compounds  thus  formed  are 
colourless,  and  so  stable,  that  they  cannot 
be  decomposed  by  other  powerful  cnemicai 
agents.  They  are  blackened  by  exposure  to 
light,  like  all  other  compounds  of  silver,  in 
consequence  of  a  part  of  the  oxide  of  silver 
which  they  contain  being  reduced  to  the 
metallic  state.  Parts  of  the  body  which 
have  united  with  salts  of  silver  no  longer 
belong  to  the  living  organism,  for  their  vital 
functions  have  been  arrested  by  combina- 
tion with  oxide  of  silver ;  and  if  they  are 
capable  of  being  reproduced,  the  neighbour- 
ing living  structures  throw  them  off  in  the 
form  of  an  eschar. 

When  nitrate  of  silver  is  introduced  into 
the  stomach,  it  meets  with  common  salt  and 
free  muriatic  acid  ;  and  if  its  quantity  is 
not  too  great,  it  is  immediately  converted 
into  chloride  of  silver — a  substance  which 
is  absolutely  insoluble  in  pure  water.  In  a 
solution  of  salt  or  muriatic  acid,  however, 
chloride  of  silver  does  dissolve  in  extremely 
minute  quantity;  and  u  is  this  small  par* 


POISONS,    CONTAGIONS,    MIASMS. 


liJ 


wnich  exercises  a  medicinal  influence  when 
nitrate  of  silver  is  administered ;  the  remain- 
ing chloride  of  silver  is  eliminated  from  the 
body  in  the  ordinary  way.  Solubility  is 
necessary  to  give  efficacy  to  any  substance 
in  the  human  body. 

The  soluble  salts  of  lead  possess  many 
properties  in  common  with  the  salts  of  silver 
and  mercury  ;  but  all  compounds  of  lead 
with  organic  matters  are  capable  of  decom- 
position by  dilute  sulphuric  acid.  The  dis- 
ease called  painter's  colic  is  unknown  in  aL 
manufactories  of  white  lead  in  which  the 
workmen  are  accustomed  to  take  as  a  pre- 
servative sulphuric  acid  lemonade  (a  solu- 
tion of  sugar  rendered  acid  by  sulphuric 
acid.) 

The  organic  substances  which  have  com- 
bined in  the  living  body  with  metallic  oxides 
or  metallic  salts,  lose  their  property  of  im- 
bibing water  and  retaining  it,  without  at  the 
same  time  being  rendered  incapable  of  per- 
mitting liquids  to  penetrate  through  their 
pores.  A  strong  contraction  and  shrinking 
of  the  surface  is  the  general  effect  of  contact 
with  these  metallic  bodies.  But  corrosive 
sublimate,  and  several  of  the  salts  of  lead, 
possess  a  peculiar  property,  in  addition  to 
those  already  mentioned.  When  they  are 
present  in  excess,  they  dissolve  the  first 
formed  insoluble  compounds,  and  thus  pro- 
duce an  effect  quite  the  reverse  of  contrac- 
tion, namely,  a  softening  of  the  part  of  the 
body  on  which  they  have  acted. 

Salts  of  oxide  of  copper,  even  when  in 
combination  with  the  most  powerful  acids, 
are  reduced  by  many  vegetable  substances, 
particularly  such  as  sugar  and  honey,  either 
into  metallic  copper,  or  into  the  red  sub- 
oxide,  neither  of  which  enters  into  combina- 
tion with  animal  matter.  It  is  well  known 
that  sugar  has  been  long  employed  as  the 
most  convenient  antidote  for  poisoning  by 
copper. 

With  respect  to  some  other  poisons, 
namely,  hyclrocyanic  acid  and  the  organic 
bases  strychnia  and  brucia,  we  are  ac- 
quainted with  no  facts  calculated  to  eluci- 
date the  nature  of  their  action.  It  may, 
however,  be  presumed  with  much  certainty, 
that  experiments  upon  their  mode  of  action 
on  differen*  animal  substances  would  very 
quickly  lead  to  the  most  satisfactory  conclu- 
sions regarding  the  cause  of  their  poisonous 
effects. 

There  is  a  peculiar  class  of  substances, 
which  are  generated  during  certain  pro- 
cesses of  decomposition,  and  which  act  upon 
the  animal  economy  as  deadly  poisons,  not 
on  account  of  their  power  of  entering  into 
combination  with  it,  or  by  reason  of  their 
eontairiing  a  poisonous  material,  but  solely 
by  virtue  of  their  peculiar  condition. 

In  order  to  attain  to  a  clear  conception  of 
the  mode  of  action  of  these  bodies,  it  is  ne- 
cessary to  call  to  mind  the  cause  on  which 
we  have  shown  the  phenomena  of  fermen- 
tation, decay,  and  putrefaction  to  depend. 

This  cause  may  be  expressed  by  the  fol- 


lowing law,  long  since  proposed  by  La  Plare 
and  Berthollet,  although  its  truth  with  re- 
spect to  chemical  phenomena  has  only  lately 
been  proved.  "*#  molecule  set  in  motion  by 
any  power  can  impart  its  own  motion  to 
another  molecule  with  which  it  may  be  in 
contact." 

This  is  a  law  of  dynamics,  the  operation 
of  which  is  manifest  in  all  cases,  in  wh.ch 
the  resistance  (/brce,  affinity,  or  cohesion,) 
opposed  to  the  motion  is  not  sufficient  to 
overcome  it. 

We  have  seen  that  ferment  or  yeast  is  a 
body  in  the  state  of  decomposition,  the 
atoms  of  which,  consequently,  are  in  a  state 
of  motion  or  transposition.  Yeast  placed 
in  contact  with  sugar  communicates  to  the 
elements  of  that  compound  the  same  state, 
in  consequence  of  which,  the  constituents 
of  the  sugar  arrange  themselves  into  new 
and  simpler  forms,  namely,  into  alcohol  and 
carbonic  acid.  In  these  new  compounds 
the  elements  are  united  together  by  stronger 
affinities  than  they  were  in  the  sugar,  and 
therefore  under  the  conditions  in  which 
they  were  produced  further  decomposition 
is  arrested. 

We  know,  also,  that  the  elements  of 
sugar  assume  totally  different  arrangements, 
when  the  substances  which  excite  their 
transposition  are  in  a  different  state  of  de- 
composition from  the  yeast  just  mentioned. 
Thus,  when  sugar  is  acted  on  by  rennet  or 
putrefying  vegetable  juices,  it  is  not  con- 
verted into  alcohol  and  carbonic  acid,  but 
into  lactic  acid,  mannite,  and  gum. 

Again,  it  has  been  shown,  that  yeast 
added  to  a  solution  of  pure  sugar  gradually 
disappears,  but  that  when  added  to  vege- 
table juices  which  contain  gluten  as  well  as 
sugar,  it  is  reproduced  by  the  decomposition 
of  the  former  substance. 

The  yeast  with  which  these  liquids  are 
made  to  ferment  has  itself  been  originally 
produced  from  gluten. 

The  conversion  of  gluten  into  yeast  in 
these  vegetable  juices  is  dependent  on  the 
decomposition  (fermentation)  of  sugar;  for, 
when  the  sugar  has  completely  disappeared, 
any  gluten  which  may  still  remain  in  the 
liquid  does  not  suffer  change  from  contact 
j  with  the  newly-deposited  yeast,  but  retains 
all  the  characters  of  gluten. 

Yeast  is  a  product  of  the  decomposition 
of  gluten  ;  but  it  passes  into  a  second  stage 
of  decomposition  when  in  contact  with 
water.  On  account  of  its  being  in  this 
state  of  further  change,  yeast  excites  fermen- 
jtation  in  a  fresh  solution  of  sugar,  and  if 
this  second  saccharine  fluid  should  contain 
gluten,  (should  it  be  wort,  for  example,) 
yeast  is  again  generated  in  consequence  of 
the  transposition  of  the  elements  of  the 
sugar  exciting  a  similar  change  in  this 
gluten. 

After  this  explanation,  the  idea  that  yeast 
reproduces  itself  as  seeds  reproduce  seeds, 
cannot  for  a  moment  be  entertained. 

From  the  foregoing  facts  it  follows,  tnat 


120 


AGRICULTURAL   CHEMISTRY. 


a  body  in  the  act  of  decomposition  (it  may 
be  named  the  exciter,}  added  to  a  mixed 
fluid  in  which  its  constituents  are  contained, 
can  reproduce  itself  in  that  fluid,  exactly  in 
the  same  manner  as  new  yeast  is  produced 
when  yeast  is  added  to  liquids  containing 

Eluten.     This  must  be  more  certainly   ef- 
>cted  when  the  liquid  acted  upon  contains 
the  body  by  the  metamorphosis  of  which  the 
exciter  has  been  originally  formed. 

It  is  also  obvious,  that  if  the  exciter  be 
able  to  impart  its  own  state  of  transformation 
to  one  only  of  the  component  parts  of  the 
mixed  liquid  acted  upon,  its  own  reproduc- 
tion may  be  the  consequence  of  the  decom- 
position of  this  one  body. 

This  law  may  be  applied  to  organic  sub- 
stances forming  part  of  the  animal  organism. 
We  know  that  all  the  constituents  of  these 
substances  are  formed  from  the  blood,  and 
that  the  blood  by  its  nature  and  constitution 
is  one  of  the  most  complex  of  all  existing 
matters. 

Nature  has  adapted  the  blood  for  the  re- 
production of  every  individual  part  of  the 
organism ;  its  principal  character  consists  in 
its  component  parts  being  subordinate  to 
every  attraction.  These  are  in  a  perpetual 
state  of  change  or  transformation,  which  is 
effected  in  the  most  various  ways  through 
the  influence  of  the  different  organs. 

The  indivdual  organs,  such  as  the  stomach, 
carsp  nil  the  organic  substances  conveyed 
t^  ili.-m  which  are  capable  of  transformation 
to  assume  new  forms.  The  stomach  com- 
pels the  elements  of  these  substances  to 
unite  into  a  compound  fitted  for  th,e  form- 
ation of  the  blood.  But  the  blood  pos- 
sesses no  power  of  causing  transformations  j 
on  the  contrary,  its  principal  character  con- 
sists in  its  readily  suffering  transformations  ; 
and  no  other  matter  can  be  compared  in  this 
respect  with  it. 

Now  it  is  a  well-known  fact,  that  when 
blood,  cerebral  substance,  gall,  pus,  and 
other  substances  in  a  state  of  putrefaction, 
are  laid  upon  fresh  wounds,  vomiting,  de- 
bility, and  at  length  death,  are  occasioned. 
It  is  also  well  known  that  bodies  in  anato- 
mical rooms  frequently  pass  into  a  state  of 
decomposition  which  is  capable  of  imparting 
itself  to  the  living  body,  the  smallest  cut 
with  a  knife  which  has  been  used  in  their 
dissection  producing  in  these  cases  dan- 
gerous consequences. 

The  poison  of  bad  sausages  belongs  to  this 
class  of  noxious  substances.  Several  hun- 
dred cases  are  known  in  which  death  has 
occurred  from  the  use  of  this  kind  of  food. 
In  Wiirtemberg  especially  these  cases  are 
Tery  frequent,  for  there  the  sausages  are  pre- 
pared from  very  various  materials.  Blood, 
liver,  bacon,  brains,  milk,  meal,  and  bread, 
are  mixed  together  with  salt  •  and  spices ; 
the  mixture  is  then  put  into  bladders  or  in- 
testines, and  after  being  boiled  is  smoked. 

When  these  sausages  are  well  prepared, 
they  may  be  preserved  for  months,  and  fur- 
nish a  nourishing  savoury  food  j  but  when 


the  spices  and  salt  are  deficient,  and  particu- 
larly when  they  are  smoked  too  late  or  nor 
sufficiently,  they  undergo  a  peculiar  kind  oi 
putrefaction,  which  begins  at  the  centre  of 
the  sausage.  Without  any  appreciable 
escape  of  gas  taking  place  they  become 
paler  in  colour,  and  more  soft  and  greasy 
in  those  parts  which  have  undergone  putre- 
faction, and  they  are  found  to  contain  free 
lactic  acid,  or  lactate  of  ammonia ;  products 
which  are  universally  formed  during'  the 
putrefaction  of  animal  and  vegetable  mat- 
ters. 

The  cause  of  the  poisonous  nature  of 
these  sausages  was  ascribed  at  first  to  hy- 
drocyanic acid,  and  afterwards  to  sebacic 
acid,  although  neither  of  these  substances 
had  been  detected  in  them.  But  sebacic 
acid  is  no  more  poisonous  than  benzoic  acid, 
with  which  it  has  so  many  properties  in 
common ;  and  the  symptoms  produced  are 
sufficient  to  show  that  hydrocyanic  acid  is 
not  the  poison. 

The  death  which  is  the  consequence  of 
poisoning  by  putrefied  sausages  succeeds 
very  lingering  and  remarkable  symptoms. 
There  is  a  gradual  wasting  of  muscular 
fibre,  and  of  all  the  constituents  of  the  body 
similarly  composed;  the  patient  becomes 
much  emaciated,  dries  to  a  complete  mum- 
my, and  finally  dies.  The  caicase  is  stiff  as 
if  frozen,  and  is  not  subject  to  putrefaction. 
During  the  progress  of  the  disease  the  saliva 
becomes  viscous  and  acquirer  an  offensive 
smell. 

Experiments  have  been  made  for  the  pur- 
pose of  ascertaining  the  pitsence  of  some 
matter  in  the  sausages  to  vkich  their  poi- 
sonous action  could  be  ascribed ;  but  no  such 
matter  has  been  detected.  Boiling  watei 
and  alcohol  completely  desiroy  the  poison- 
ous properties  of  the  sausages,  without 
themselves  acquiring  similar  properties. 

Now  this  is  the  peculiar  character  of  all 
substances  which  exert  an  action  by  virtue 
of  their  existing  condition — of  those  bodies 
the  elements  of  which  are  in  the  state  of  de- 
composition or  transposition ;  a  state  which 
is  destroyed  by  boiling  water  and  alcohol 
without  the  cause  of  the  influence  being  im- 
parted to  those  liquids;  for  a  state  of  action 
or  power  cannot  be  preserved  in  a  liquid. 

Sausages,  in  the  state  here  described,  ex- 
ercise an  action  upon  the  organism,  in  con- 
sequence of  the  stomach  and  other  parts 
with  which  they  come  in  contact  not  having 
the  power  to  arrest  their  decomposition ;  and 
entering  the  blood  in  some  way  or  other, 
while  still  possessing  their  whole  power, 
they  impart  their  peculiar  action  to  the  con- 
stituents of  that  fluid. 

The  poisonous  properties  of  decayed  sau- 
sages are  not  destroyed  by  the  stomach  as 
those  of  the  small-pox  virus  are.  All  the 
substances  in  the  body  capable  of  putrefac- 
tion are  gradually  decomposed  during  the 
course  of  the  disease,  and  after  death  nothing 
remains  except  fat,  tendons,  bones,  and  a 
few  other  substances  which  are  incapable  of 


POISONS,   CONTAGIONS,   MIASMS. 


121 


putrefying  in  the  conditions  afforded  by  the 
body. 

It  is  impossible  to  mistake  the  modus  ope- 
randi  of  this  poison,  for  Colin  has  clearly 
proved  that  muscle,  urine,  cheese,  cerebral 
substance,  and  other  matters,  in  a  state  of 
putrefaction,  communicate  their  own  state 
of  decomposition  to  substances  much  less 
prone  to  change  of  composition  than  the 
blood.  When  placed  in  contact  with  a  so- 
lution of  sugar,  they  cause  its  putrefaction, 
or  the  transposition  of  its  elements  into  car- 
bonic acid  and  alcohol. 

When  putrefying  muscle  or  pus  is  placed 
upon  a  fresh  wound,  it  occasions  disease 
and  death.  It  is  obvious  that  these  sub- 
stances communicate  their  own  state  of  pu- 
trefaction to  the  sound  blood  from  which  they 
were  produced,  exactly  in  the  same  manner 
as  gluten  in  a  state  ot  decay  or  putrefaction 
causes  a  similar  transformation  in  a  solution 
of  sugar. 

Poisons  of  this  kind  are  even  generated 
by  the  body  itself  in  particular  diseases.  In 
small-pox,  plague,  and  syphilis,  substances 
of  a  peculiar  nature  are  formed  from  the 
constituents  of  the  blood.  These  matters 
are  capable  of  inducing  in  the  blood  of  a 
healthy  individual  a  decomposition  similar 
to  that  of  which  they  themselves  are  the 
subjects ;  in  other  words,  they  produce  the 
same  disease.  The  morbid  virus  appears  to 
reproduce  itself  just  as  seeds  appear  to  re- 
produce seeds. 

The  mode  of  action  of  a  morbid  virus  ex- 
hibits such  a  strong  similarity  to  the  action 
of  yeast  upon  liquids  containing  sugar  and 
gluten,  that  the  two  processes  have  been 
long  since  compared  to  one  another,  al- 
though merely  for  the  purpose  of  illustra- 
tion. But  when  the  phenomena  attending 
the  action  of  each  respectively  are  con- 
sidered more  closely,  it  will  in  reality  be 
seen  that  their  influence  depends  upon  the 
same  cause. 

In  dry  air,  and  in  the  absence  of  mois- 
ture, all  these  poisons  remain  for  a  long  time 
unchanged ;  but  when  exposed  to  the  air  in 
the  moist  condition,  they  lose  very  rapidly 
their  peculiar  properties.  In  the  former 
case,  those  conditions  are  afforded  which  ar- 
rrst  their  decomposition  without  destroying 
it ;  in  the  latter,  all  the  circumstances  neces- 
sary for  the  completion  of  their  decomposi- 
tion are  presented. 

The  temperature  at  which  water  boils, 
and  contact  with  alcohol,  render  such  poi- 
sons inert.  Acids,  salts  of  mercury,  sul- 
phurous acid,  chlorine,  iodine,  bromine, 
aromatic  substances,  volatile  oils,  and  parti- 
cularly empyreumatic  oils,  smoke,  and  a 
decoction  of  coffee,  completely  destroy  their 
contagious  properties,  in  some  cases  com- 
bining with  them  or  otherwise  effecting 
their  decomposition.  Now  all  these  agents, 
without  exception,  retard  fermentation,  pu- 
trefaction, and  decay,  and  when  present  in 
sufficient  quantity,  completely  arrest  these 
processes  of  deco  nposition. 
16 


A  peculiar  matter,  to  which  the  poisonous 
action  is  due,  cannot,  we  have  seen,  be  ex- 
tracted from  decayed  sausages :  and  it  is 
equally  impossible  to  obtain  such  a  principle 
from  the  virus  of  small-pox  or  plague,  and 
for  this  reason,  that  their  peculiar  power  is 
due  to  an  active  condition  recognisable  ny 
our  senses,  only  through  the  phenomena 
which  it  produces. 

In  order  to  explain  the  effects  of  conta- 
gious matters,  a  peculiar  principle  of  life  has 
been  ascribed  to  them — a  life  similar  to  that 
possessed  by  the  germ  of  a  seed,  which 
enables  it  under  favourable  conditions  to  de- 
velope  and  multiply  itself.  It  would  be  im- 
possible to  find  a  more  correct  figurative 
representation  of  these  phenomena ;  it  is  one 
which  is  applicable  to  contagions,  as  well 
as  to  ferment,  to  animal  and  vegetable  sub- 
stances in  a  state  of  fermentation,  putrefac- 
tion or  decay,  and  even  to  a  piece  of  decay- 
ing wood,  which  by  mere  contact  with  fresh 
wood,  causes  the  latter  to  undergo  gradually 
the  same  change  and  become  decayed  and 
mouldered. 

If  the  properly  possessed  by  a  body  of 
producing  such  a  change  in  any  other  sub- 
stance as  causes  the  reproduction  of  itself, 
with  all  its  properties,  be  regarded  as  life, 
then,  indeed,  all  the  above  phenomena  may 
be  ascribed  to  life.  But  in  that  case  the} 
must  not  be  considered  as  the  only  processes 
due  to  vitality,  for  the  above  interpretation 
of  the  expression  embraces  the  majority  ^t' 
the  phenomena  which  occur  in  organic  che  - 
mistry.  Life  would,  according  to  that  view, 
be  admitted  to  exist  in  every  body  in  which 
chemical  forces  act. 

If  a  body  A ,  for  example  oxamide,  (a  sub- 
stance  scarcely  soluble  in  water,  and  without 
the  slightest  taste,)  be  brought  into  contact 
with  another  compound  B,  which  is  to  be 
reproduced;  and  if  this  second  body  be  oxalic 
acid  dissolved  in  water;  then  the  following 
changes  are  observed  to  take  place : — The 
oxamide  is  decomposed  by  the  oxalic  acid, 
provided  the  conditions  necessary  for  their 
exercising  an  action  upon  one  another  are 
present.  The  elements  of  water  unite  with 
the  constituents  of  oxamide,  and  ammonia  is 
one  product  formed,  and  oxalic  acid  the 
other,  both  in  exactly  the  proper  proportions 
to  combine  and  form  a  neutral  salt. 

Here  the  contact  of  oxamide  and  oxalic 
acid  induces  a  transformation  of  the  oxa- 
mide, which  is  decomposed  into  oxalic  acid 
and  ammonia.  The  oxalic  acid  thus  formed, 
as  well  as  that  originally  added,  are  shared 
by  the  ammonia — or  m  other  words,  as 
much  free  oxalic  acid  exists  after  the  de- 
composition as  before  it,  und  is  of  course 
still  possessed  of  its  original  power.  It  mat- 
ters not  whether  the  free  oxalic  acid  is  that 
originally  added,  or  that  newly  produced; 
it  is  certain  that  it  has  been  reproduced  in  an 
equal  quantity  by  the  decomposition. 

If  we  now  add  to  the  same  mixture  a  fresh 
portion  of  oxamide,  exactly  equal  in  quan- 
tity to  that  first  used,  and  treat  it  in  the  same 


122 


AGRICULx 


manner,  the  same  decomposition  is  repeated ; 
the  free  oxalic  acid  enters  into  combination,, 
whilst  another  portion  is  liberated.  In  this 
manner  a  very  minute  quantity  of  oxalic 
acid  may  be  made  to  effect  the  decomposi- 
tion of  several  hundred  pounds  of  oxamide; 
and  one  grain  of  the  acid  to  reproduce  itself 
ji  unlimited  quantity. 

We  know  that  the  contact  of  the  virus  of 
small-pox  causes  such  a  change  in  the  blood, 
as  gives  rise  to  the  reproduction  of  the  poi- 
son from  the  constituents  of  the  fluid.  This 
transformation  is  not  arrested  until  all  the 
particles  of  the  blood  which  are  susceptible 
of  the  decomposition  have  undergone  the 
metamorphosis.  We  have  just  seen  that 
the  contact  of  oxalic  acid  with  oxamide 
caused  the  production  of  fresh  oxalic  acid, 
which  in  its  turn  exercised  the  same  action 
on  a  new  portion  of  oxamide.  The  trans- 
formation was  only  arrested  in  consequence 
of  the  quantity  of  oxamide  present  being 
limited.  In  their  form  both  these  transform- 
ations belong  to  the  same  class.  But  no 
one  except  a  person  quite  unaccustomed  to 
view  such  changes  will  ascribe  them  to  a 
vital  power,  although  we  admit  they  cor- 
respond remarkably  to  our  common  concep- 
tions of  life;  they  are  really  chemical  pro- 
cesses dependent  upon  the  common  chemical 
forces. 

Our  notion   of  life  involves  something 
more  than  mere  reproduction,  namely,  the  ! 
idea  of  an  active  power  exercised  by  virtue  ^ 
of  a  definite  form,  and  production  and  gene-  j 
ration  in  a  definite   form.      By  chemical 
agency  we  can  produce  the  constituents  of  j 
muscular  fibre,  skin,  and  hair ;  but  we  can 
form  by  their  means  no  organized  tissue,  no 
organic  cell. 

The  production  of  organs,  the  co-opera- 
tion of  a  system  of  organs,  and  their  power 
not  only  to  produce  their  component  parts 
from  the  food  presented  to  them,  but  to 
generate  themselves  in  their  original  form 
and  with  all  their  properties,  are  characters 
belonging  exclusively  to  organic  life,  and 
constitute  a  form  of  reproduction  indepen- 
dent of  chemical  powers. 

The  chemical  forces  are  subject  to  the 
invisible  cause  by  which  this  form  is  pro- 
duced. Of  the  existence  of  this  cause  itself 
we  are  made  aware  only  by  the  phenomena 
which  it  produces.  Its  laws  must  be  inves- 
tigated just  as  we  investigate  those  of  the 
other  powers  which  affect  motion  and 
changes  in  matter. 

The  chemical  forces  are  subordinate  to 
this  cause  of  life,  just  as  they  are  to  elec- 
tricity, heat,  mechanical  motion,  and  fric- 
tion. By  the  influence  of  the  latter  forces, 
they  suffer  changes  in  their  direction,  an  in- 
crease or  diminution  of  their  intensity,  or  a 
complete  cessation  or  reversal  of  their  action. 

Such  an  influence  and  no  other  is  exer- 
tised  by  the  vital  principle  over  the  chemical 
forces;  but  in  every  case  where  combination 
or  decomposition  takes  place,  chemical  affini- 
ty and  cohesion  are  in  action 


The  vital  principle  is  only  known  to  us 
through  the  peculiar  form  of  its  instruments, 
that  is,  through  the  organs  in  which  it  re- 
sides. Hence,  whatever  kind  of  energy  a 
a  substance  may  possess,  if  it  is  amorphous 
and  destitute  of  organs  from  which  the  im- 
pulse, motion  or  change  proceeds,  it  does 
not  live.  Its  energy  depends  in  this  case  on 
a  chemical  action.  Light,  heat,  electricity, 
or  other  influences  may  increase,  diminish, 
or  arrest  this  action,  but  they  are  not  its  effi 
cient  cause. 

In  the  same  way  the  vital  principle  go- 
verns the  chemical  powers  in  the  living  body. 
All  those  substances  to  which  we  apply  the 
general  name  of  food,  and  all  the  bodies 
formed  from  them  in  the  organism,  are  che- 
mical compounds.  The  vital  principle  has, 
therefore,  no  other  resistance  to  overcome, 
in  order  to  convert  these  substances  into 
component  parts  of  the  organism,  than  the 
chemical  powers  by  which  their  constituents 
are  held  together.  If  the  food  possessed 
life,  not  merely  the  chemical  forces,  but  this 
vitality,  would  offer  resistance  to  the  vital 
force  of  the  organism  it  nourished. 

All  substances  adapted  for  assimilation 
are  bodies  of  a  very  complex  constitution ; 
their  atoms  are  highly  complex,  and  are 
held  together  only  by  a  weak  chemical 
action.  They  are  formed  by  the  union 
of  two  or  more  simple  compounds;  and  in 
proportion  as  the  number  of  their  atoms 
augments  their  disposition  to  enter  into  new 
combinations  is  diminished ;  that  is,  they 
lose  the  power  of  acting  chemically  upon 
other  bodies. 

Their  complex  nature,  however,  renders 
them  more  liable  to  be  changed,  by  the 
agency  of  external  causes,  and  thus  to  suffer 
decomposition.  Any  external  agency,  in 
many  cases  even  mechanical  friction,  is 
sufficient  to  cause  a  disturbance  in  the  equi- 
librium of  the  attraction  of  their  constitu- 
ents; they  arrange  themselves  either  into 
new,  more  simple,  and  permanent  combina- 
tions, or  if  a  foreign  attraction  exercise  its 
influence  upon  it,  they  arrange  themselves 
in  accordance  with  that  attraction. 

The  special  characters  of  food,  that  is,  of 
substances  fitted  for  assimilation,  are  absence 
of  active  chemical  properties,  and  the  capa- 
bility of  yielding  to  transformations. 

The  equilibrium  in  the  chemical  attrac- 
tions of  the  constituents  of  the  food  is  dis- 
turbed by  the  vital  principle,  as  we  know  it 
may  be  by  many  other  causes.  But  the 
union  of  its  elements,  so  as  to  produce  new 
combinations  and  forms,  indicates  the  pre- 
sence of  a  peculiar  mode  of  attraction,  and 
the  existence  of  a  power  distinct  from  all 
other  powers  of  nature,  namely,  the  vital 
principle. 

All  bodies  of  simple  composition  possess 
a  greater  or  less  disposition  to  form  combi- 
nations. Thus  oxalic  acid  is  one  of  the 
simplest  of  the  organic  acids,  while  stearic 
acid  is  one  of  the  most  complex ;  and  the 
former  is  the  strongest,  the  latter  one  of  the 


POISONS,   CONTAGIONS,   MIASMS. 


123 


weakest,  in  respect  to  active  chemical  cha- 
racter. By  virtue  of  this  disposition,  simple 
compounds  produce  changes  in  every  body 
which  offers  no  resistance  to  their  action; 
they  enter  into  combination  and  cause  de- 
composition. 

The  vital  principle  opposes  to  the  con- 
tinual action  of  the  atmosphere,  moisture 
and  temperature  upon  the  organism,  a  re- 
sistance which  is,  in  a  certain  degree,  invin- 
cible. It  is  by  the  constant  neutralization 
and  renewal  of  these  external  influences 
that  life  and  motion  are  maintained. 

The  greatest  wonder  in  the  living  organ- 
ism is  the  fact  that  an  unfathomable  wisdom 
has  made  the  cause  of  a  continual  decom- 
position pr  destruction,  namely,  the  support 
of  the  process  of  respiration,  to  be  the  means 
of  renewing  the  organism,  and  of  resisting 
all  the  other  atmospheric  influences,  such 
as  those  of  moisture  and  changes  of  tem- 
perature. 

When  a  chemical  compound  of  simple 
constitution  is  introduced  into  the  stomach, 
or  any  other  part  of  the  organism,  it  must 
exercise  a  chemical  action  upon  all  sub- 
stances with  which  it  comes  in  contact ;  for  we 
know  the  peculiar  character  of  such  a  body 
to  be  an  aptitude  and  power  to  enter  into 
combinations  and  effect  decompositions. 

The  chemical  action  of  such  a  compound 
is  of  course  opposfed  by  the  vital  principle. 
The  results  produced  depend  upon  the 
strength  of  their  respective  actions :  either 
an  equilibrium  of  both  powers  is  attained, 
a  change  being  effected  without  the  destruc- 
tion of  the  vital  principle,  in  which  case  a 
medicinal  effect  is  occasioned ;  or  the  acting 
body  yields  to  the  superior  force  of  vitality, 
that  is,  it  is  digested;  or  lastly,  the  chemical 
action  obtains  the  ascendency  and  acts  as  a 
poison. 

Every  substance  may  be  considered  as 
nutriment,  which  loses  its  former  properties 
when  acted  on  by  the  vital  principle,  and 
does  not  exercise  a  chemical  action  upon  the 
living  organ. 

Another  cla^s  of  bodies  change  the  direc- 
tion, the  strength,  and  intensity  of  the  re- 
sisting force,  (the  vital  principle,)  and  thus 
exert  a  modifying  influence  upon  the  func- 
tions of  its  organs.  They  produce  a  dis- 
turbance in  the  system,  either  by  their  pre- 
sence, or  by  themselves  undergoing  a  change ; 
these  are  medicaments. 

A  third  class  of  compounds  are  called 
poisons,  when  they  possess  the  property  of 
uniting  with  organs  or  with  their  component 
parts,  and  when  their  power  of  effecting 
this  is  stronger  than  the  resistance  offered 
by  thp  vital  principle. 

The  quantity  of  a  substance  and  its  con- 
dition must,  obviously,  completely  change 
the  mode  of  its  chemical  action. 

Increase  of  quantity  is  known  to  be  equi- 
valent to  superior  affinity.     Hence  a  medica- 
ment administered  in  excessive  quantity  may  i 
act  as  a  poison,  and  a  poison  in  small  doses 
as  a  medicament. 


Food  will  act  as  a  poison,  that  is,  i.  will 
produce  disease,  when  it  is  able  to  exercise 
a  chemical  action  by  virtue  of  its  quantity ; 
or,  when  either  its  condition  or  its  presence 
retards,  prevents,  or  arrests  the  motion  ot 
any  organ. 

A  compound  acts  as*  a  poison  when  all  the 
parts  of  an  organ  with  which  it  is  brought 
into  contact  enter  into  chemical  combination 
with  it,  while  it  may  operate  as  a  medicine, 
when  it  produces  only  a  partial  change. 

No  other  component  part  of  the  organism 
can  be  compared  to  the  blood,  in  respect  of 
the  feeble  resistance  which  it  offers  to  exte- 
rior influences.  The  blood  is  not  an  organ 
which  is  formed,  but  an  organ  in  the  act  of 
formation  ;  indeed,  it  is  the  sum  of  all  the 
organs  which  are  being  formed.  The  che^ 
mical  force  and  the  vital  principle  hold  each 
other  in  such  perfect  equilibrium,  that  every 
disturbance,  however  trifling,  or  from  what- 
ever cause  it  may  proceed,  effects  a  change 
in  the  blood.  This  liquid  possesses  so  little 
of  permanence,  that  it  cannot  be  removed 
from  the  body  without  immediately  suffer- 
ing a  change,  and  cannot  come  in  contact 
with  any  organ  in  the  body,  without  yielding 
to  its  attraction. 

The  slightest  action  of  a  chemical  agent 
upon  the  blood  exercises  an  injurious  influ- 
ence ;  even  the  momentary  contact  with  the 
air  in  the  lungs,  although  effected  through 
the  medium  of  cells  and  membranes,  alters 
the  colour  and  other  qualities  of  the  blood. 
Every  chemical  action  propagates  itself 
through  the  mass  of  the  blood ;  for  exam- 
ple, the  active  chemical  condition  of  the 
constituents  of  a  body  undergoing  decom- 
position, fermentation,  putrefaction,  or  de- 
cay, disturbs  the  equilibrium  between  the 
chemical  force  and  the  vital  principle  in  the 
circulating  fluid.  Numerous  modifications 
in  the  composition  and  condition  of  the 
compounds  produced  from  the  elements  of 
the  blood,  result  from  the  conflict  of  the  vital 
force  with  the  chemical  affinity,  in  their  in  - 
cessant  endeavour  to  overcome  one  another. 

All  the  characters  of  the  phenomena  of 
contagion  tend  to  disprove  the  existence  of 
life  in  contagious  matters.  They  without 
doubt  exercise  an  influence  very  similar  to 
some  processes  in  the  living  organism;  but 
the  cause  of  this  influence  is  chemical  ac- 
tion, which  is  capable  of  being  subdued  by 
other  chemical  actions,  by  opposed  agencies. 

Several  of  the  poisons  generated  in  the 
body  by  disease  lose  all  their  power  when 
introduced  into  the  stomach,  but  others  are 
not  thus  destroyed. 

It  is  a  fact  very  decisive  of  their  chemical 
nature  and  mode  of  action,  that  those  poi- 
sons which  are  neutral  or  alkaline,  such  as 
t«he  poisonous  matter  of  the  contagious  fever 
in  cattle  (typhus  conta^iosm  ruminantium.) 
or  that  of  the  srnail-pox,  lose  their  whole 
power  of  contagion  in  the  stomach  ;  whilst 
that  of  sausages,  which  has  an  acid  reac- 
tion, retains  all  its  frightful  properties  under 
the  same  circumstances. 


124 


AGRICULTURAL   CHEMISTRY. 


In  the  former  of  these  cases,  the  free  acid 
present  in  the  stomach  destroys  the  action 
of  the  poison,  the  .chemical  properties  of 
which  are  opposed  to  it ;  whilst  in  the  latter 
it  strengthens,  or  at  ail  events  does  not  offer 
any  impediment  to  poisonous  action. 
,  Microscopical  examination  has  detected 
peculiar  bodies  resembling  the  globules  of 
the  blood  in  malignant'  putrefying  pus,  in 
the  matter  of  vaccine,  &c.  The  presence 
of  tnese  bodies  has  given  weight  to  the 
opinion,  that  contagion  proceeds  from  the 
developement  of  a  diseased  organic  life ; 
and  these  formations  have  been  regarded  as 
the  living  seeds  of  disease. 

This  view,  which  is  not  adapted  to  dis- 
cussion, has  led  those  philosophers  who  are 
accustomed  to  search  for  explanations  of 
phenomena  in  forms,  to  consider  the  yeast 
produced  by  the  fermentation  of  beer  as  pos- 
sessed of  life.  They  have  imagined  it  to 
be  composed  of  animals  or  plants,  which 
nourish  themselves  from  the  sugar  in  which 
they  are  placed,  and  at  the  same  time  yield 
alcohol  and  carbonic  acid  as  excrementitious 
matters.* 

It  would  perhaps  appear  wonderful  if 
bodies,  possessing  a  crystalline  structure  and 
geometrical  figure,  were  formed  during  the 
processes  of  fermentation  and  putrefaction 
from  the  organic  substances  .and  tissues  of 
organs.  We  know,  on  the  contrary,  that 
the  complete  dissolution  into  organic  com- 
pounds is  preceded  by  a  series  of  trans- 
formations, in  which  the  organic  structures 
gradually  resign  their  forms. 

Blood,  in  a  state  of  decomposition,  may 
appear  to  the  eye  unchanged ;  and  when  we 
recognise  the  globules  of  blood  in  a  liquid 
contagious  matter,  the  utmost  that  we  can 
thence  infer  is,  that  those  globules  have 
taken  no  part  in  the  process  of  decomposi- 
tion. All  the  phosphate  of  lime  may  be 
removed  from  bones,  leaving  them  trans- 
parent and  flexible  like  leather,  without  the 
form  of  the  bones  being  in  the  smallest  de- 
gree lost  Again,  bones  may  be  burned 
until  they  be  quite  white,  and  consist  merely 
of  a  skeleton  of  phosphate  of  lime,  but  they 
will  still  possess  their  original  form.  In  the 
same  way  processes  of  decomposition  in 
the  blood  may  affect  individual  constitu- 
ents only  of  that  fluid,  which  will  become 
destroyed  and  disappear,  whilst  its  other 
parts  will  maintain  the  original  form. 

Several  kinds  of  contagion  are  propagated 
through  the  air:  so  that,  according  to  the 
view  already  mentioned,  we  must  ascribe 
life  to  a  gas,  that  is,  to  an  aeriform  body. 

A I  the  supposed  proofs  of  the  vitality  of 
contagions  are  merely  ideas  and  figurative 
representations,  fitted  to  render  the  pheno- 
mena more  easy  of  apprehension  by  our 
senses,  without  explaining  them.  These 
figurative  expressions,  with  which  we  are 
BO  willingly  and  easily  satisfied  in  all 

*  Annalen  der  Pharmacie,  Band  xxix.  S.  93 
ttnd  100. 


sciences,  are  the  foes  of  all  inquiries  into  the 
mysteries  of  nature ;  they  are  like  the  fata 
morgana,  which  show  us  deceitful  views  of 
seas,  fertile  fields,  and  luscious  fruits,  but 
leave  us  languishing  when  we  have  most 
need  of  what  they  promise. 

It  is  certain  that  the  action  of  contagions 
is  the  result  of  a  peculiar  influence  depend- 
ent on  chemical  forces,  and  in  no  way  con- 
nected with  the  vital  principle.  This  in- 
fluence is  destroyed  by  chemical  actions, 
and  manifests  itself  wherever  it  is  not  sub- 
dued by  some  antagonist  power.  Its  exist- 
ence is  recognised  in  a  connected  series  of 
changes  and  transformations,,  in  which  it 
causes  all  substances  capable  of  undergoing 
similar  changes  to  participate. 

An  animal  substance  in  the  act  of  decom- 
position, or  a  substance  generated  from  the 
component  parts  of  a  living  body  by  disease, 
communicates  its  own  condition  to  all  parts 
of  the  system  capable  of  entering  into  the 
same  state,  if  no  cause  exist  in  these  parts 
by  which  the  change  is  counteracted  or  de- 
stroyed. 

Disease  is  excited  by  contagion. 

The  transformations  produced  by  the  dis- 
ease assume  a  series  of  forms. 

In  order  to  obtain  a  clear  conception  of 
these  transformations,  we  may  consider  the 
changes  which  substances,  more  simply 
composed  than  the  living  body,  suffer  from 
the  influence  of  similar  causes.  When  pu- 
trefying blood  or  yeast  in  the  act  of  trans- 
formation is  placed  in  contact  with  a  solu- 
tion of  sugar,  the  elements  of  the  latter 
substance  are  transposed,  so  as  to  form  al- 
cohol and  carbonic  acid. 

A  piece  of  the  rennet-stomach  of  a  calf 
in  a  state  of  decomposition  occasions  the 
elements  of  sugar  to  assume  a  different  ar- 
rangement. The  sugar  is  converted  into 
lactic  acid  without  the  addition  or  loss  of 
any  element.  (1  atom  of  sugar  of  grapes 
C1'2  H12  O12  yields  two  atoms  of  lactic 
acid=2  (C6  H6/O6.) 

When  the  juice  of  onions  or  of  beet- root 
is  made  to  ferment  at  high  temperatures, 
lactic  acid,  mannite,  and  gum  are  formed. 
Thus,  according  to  the  different  states  of  the 
transposition  of  the  elements  of  the  exciting 
body,  the  elements  of  the  sugar  arrange 
themselves  in  different  manners,  that  is,  dif- 
ferent products  are  formed. 

The  immediate  contact  of  the  decompos- 
ing substance  with  the  sugar  is  the  cause 
by  which  its  particles  are  made  to  .assume 
new  forms  and  natures.  The  removal  of 
that  substance  occasions  the  cessation  of  the 
decomposition  of  the  sugar,  so  that  should 
its  transformation  be  completed  before  the 
sugar,  the  latter  can  suffer  no  further 
change. 

In  none  of  these  processes  of  decomposi- 
tion is  the  exciting  body  reproduced;  for 
the  conditions  necessary  tc  its  reproduction 
do  not  exist  in  the  elements  of  the  sugar. 

Just  as  yeast,  putrefying  flesh,  and  the 
stomach  of  a  calf  in  a  state  of  decompcsi 


POISONS,   CONTAGIONS,   MIASMS. 


125 


tion,  when  introduced  into  solutions  of 
sugar,  effect  the  transformation  of  this  sub- 
stance, without  being  themselves  regene- 
rated; in  the  same  manner,  miasms  and 
certain  contagious  matters  produce  diseases 
in  the  human  organism,  by  communicating 
the  state  of  decomposition  of  which  they 
themselves  are  the  subject,  to  certain  parts 
of  the  organism,  without  themselves  being 
reproduced  in  their  peculiar  form  and  na- 
ture during  the  progress  of  the  decompo- 
sition. 

The  disease  in  this  case  is  not  contagious. 

Now  when  yeast  is  introduced  into  a 
mixed  liquid  containing  both  sugar  and  glu- 
ten, such  as  wort,  the  act  of  decomposition 
of  the  sugar  effects  a  change  in  the  form  and 
mature  of  the  gluten,  which  is,  in  conse- 
quence, also  subjected  to  transformation. 
As  long  as  some  of  the  fermenting  sugar  re- 
mains, gluten  continues  to  be  separated  as 
yeast,  and  this  new  matter  in  its  turn  ex- 
cites fermentation  in  a  fresh  solution  of 
sugar  or  wort.  If  the  sugar,  however, 
should  be  first  decomposed,  the  gluten  which 
remains  in  solution  is  not  converted  into 
yeast.  We  see,  therefore,  that  the  repro- 
duction of  the  exciting  body  here  depends — 

1 .  Upon  the  presence  of  that  substance 
from  which  it  was  originally  formed ; 

2.  Upon  the  presence   of  a  compound 
which  is  capable  of  being  decomposed  by 
contact  with  the  exciting  body. 

If  we  express  in  the  same  terms  the  re- 
production of  contagious  matter  in  conta- 
gious diseases,  since  it  is  quite  certain  that 
they  must  have  their  origin  in  the  blood,  we 
must  admit  that  the  blood  of  a  healthy  indi- 
vidual contains  substances,  by  the  decompo- 
sition of  which  the  exciting  body  or  conta- 
gion can  be  produced.  It  must  further  be 
admitted,  when  contagion  results,  that  the 
blood  contains  a  second  constituent  capable 
of  being  decomposed  by  the  exciting  body. 
It  is  only  in  consequence  of  the  conversion 
of  the  second  constituent,  that  the  original 
exciting  body  can  be  reproduced. 

A  susceptibility  of  contagion  indicates  the 
presence  of  a  certain  quantity  of  this  second 
body  in  the  blood  of  a  healthy  individual. 
The  susceptibility  for  the  disease  and  its  in- 
tensity must  augment  according  to  the  quan- 
tity of  that  body  present  in  the  blood  j  and 
in  proportion  to  its  diminution  or  disappear- 
ance, the  course  of  the  disease  will  change. 

When  a  quantity,  however  small,  of  con- 
tagious matter,  that  is  of  the  exciting  body, 
is  introduced  into  the  blood  of  a  healthy  in- 
dividual, it  will  be  again  generated  in  the 
blood,  just  as  yeast  is  reproduced  from  wort. 
Its  condition  of  transformation  will  be  com- 
municated to  a  constituent  of  the  blood ;  and 
in  consequence  of  the  transformation  suf- 
fered Hy  this  substance,  a  body  identical  with 
or  similar  to  the  exciting  or  contagious  mat- 
ter will  be  produced  from  another  consti- 
tuent substance  of  the  blood.  The  quantity 
of  the  exciting  body  newly  produced  must 
constantly  augment,  if  its  Jturther  trans- 


formation or  decomposition  proceeds  more 
slowly  than  that  of  the  compound  in  the 
blood,  the  decomposition  of  which  it  effects. 

If  the  transformation  of  the  yeast  gene- 
rated in  the  fermentation  of  wort  proceeded 
with  the  same  rapidity  as  that  of  the  parti- 
cles of  the  sugar  contained  in  it,  both  would 
simultaneously  disappear  when  the  ferment- 
ation was  completed.  But  yeast  requires  a 
much  longer  time  for  decomposition  than 
sugar,  so  that  after  the  latter  has  completely 
disappeared,  there  remains  a  much  larger 
quantity  of  yeast  than  existed  in  the  fluid  at 
the  commencement  of  the  fermentation,— 
yeast  which  is  still  in  a  state  of  incessant 
progressive  transformation,  and  therefore 
possessed  of  its  peculiar  property. 

The  state  of  change  or  decomposition 
which  affects  one  particle  of  blood,  is  im- 
parted to  a  second,  a  third,  and  at  last  to  all 
the  particles  of  blood  in  the  whole  body. 
It  is  communicated  in  like  manner  to  the 
blood  of  another  individual,  to  that  of  a 
third  person,  and  so  on — or  in  other  words, 
the  disease  is  excited  in  them  also. 

It  is  quite  certain  that  a  number  of  pecu- 
liar substances  exist  in  the  blood  of  some 
men  and  animals,  which  are  absent  from 
the  blood  of  others. 

The  blood  of  the  same  individual  contains, 
in  childhood  and  youth,  variable  quantities 
of  substances,  which  are  absent  from  it  in 
other  stages  of  growth.  The  susceptibility 
of  contagion  by  peculiar  exciting  bodies  in 
childhood,  indicates  a  propagation  and  re- 
generation of  the  exciting  bodies,  in  con- 
sequence of  the  transformation  of  certain 
substances  which  are  present  in  the  blood, 
and  in  the  absence  of  which  no  contagion 
could  ensue.  The  form  of  a  disease  is 
termed  benignant,  when  the  tranformations 
are  perfected  on  constituents  of  the  body 
which  are  not  essential  to  life,  without  the 
other  parts  taking  a  share  in  the  decomposi- 
tion ;  it  is  termed  malignant  when  they 
affect  essential  organs. 

It  cannot  be  supposed  that  the  different 
changes  in  the  blood,  by  which  its  constitu- 
ents are  converted  into  fat,  muscular  fibre, 
substance  of  the  brain  and  nerves,  bones, 
hair,  &c.,  and  the  transformation  of  food  into 
blood,  can  take  place  without  the  simulta- 
neous formation  of  new  compounds  which 
require  to  be  removed  from  the  body  by  the 
organs  of  excretion. 

In  an  adult  these  excretions  do  not  vary 
much  either  in  their  nature  or  quantity. 
The  food  taken  is  not  employed  in  increasing 
the  size  of  the  body,  but  merely  for  the  pur- 
pose of  replacing  any  substances  which  may 
be  consumed  by  the  various  actions  in  the 
organism ;  every  motion,  every  manifesta- 
tion of  organic  properties,  and  every  organic 
action  being  attended  by  a  change  in  the 
material  of  the  body,  and  by  the  assumption 
of  a  new  form  by  its  constituents.* 


*  The  experiments  of  Barruel  upon  the  dif- 
ferent odours  emitted  from  blood  on  the  addition 


126 


AGRICULTURAL  CHEMISTRY. 


But  in  a  child  this  normal  condition  of 
sustenance  is  accompanied  by  an  abnormal 
condition  of  growth  and  increase  in  the  size 
of  the  body,  and  of  each  individual  part  of 
it.  Hence  there  must  be  a  much  larger 
quantity  of  foreign  substances,  not  belong- 
ing to  the  organism,  diffused  through  every 
part  of  the  blood  in  the  body  of  a  young 
individual. 

When  the  organs  of  secretion  are  in  pro- 
per action,  these  substances  will  be  re- 
moved from  the  system ;  but  when  the  func- 
tions of  those  organs  are  impeded,  they  will 
remain  in  the  blood  or  become  accumulated 
in  particular  parts  of  the  body.  The  skin, 
lungs,  and  other  organs,  assume  the  func- 
tions of  the  diseased  secreting  organs,  and 
the  accumulated  substances  are  eliminated 
by  them.  If,  when  thus  exhaled,  these  sub- 
stances happen  to  be  in  the  state  of  progres- 
sive transformation,  they  are  contagious; 
that  is,  they  are  able  to  produce  the  same 
state  of  disease  in  another  healthy  organism, 
provided  the  latter  organism  is  susceptible 
of  their  action — or  in  other  words,  contains 
a  matter  capable  of  suffering  the  same  pro- 
cess of  decomposition. 

The  production  of  matters  of  this  kind, 
which  render  the  body  susceptible  of  conta- 
gion, may  be  occasioned  by  the  manner  of 
living,  or  by  the  nutriment  taken  by  an  in- 
dividual. A  superabundance  of  strong  and 
otherwise  wholesome  food  may  produce 
them,  as  well  as  a  deficiency  of  nutriment, 
uncleanliness,  or  even  the  use  of  decayed 
substances  as  food. 

All  these  conditions  for  contagion  must  be 
considered  as  accidental.  Their  formation 
and  accumulation  in  the  body  may  be  pre- 
vented, and  they  may  even  be  removed  from 
it  without  disturbing  its  most  important 
functions  of  health.  Their  presence  is  not 
necessary  to  life. 

The  action,  as  well  as  the  generation  of 
the  matter  of  contagion  is,  according  to  this 
view,  a  chemical  process  participated  in  by 
all  substances  in  the  living  body,  and  by  all 
the  constituents  of  those  organs  in  which 
the  vital  principle  does  not  overcome  the 
chemical  action.  The  contagion,  accord- 
ingly, either  spreads  itself  over  every  part 
of  the  body,  or  is  confined  particularly  to 
certain  organs,  that  is,  the  disease  attacks 
all  the  organs  or  only  a  few  of  them,  ac- 
cording to  the  feebleness  or  intensity  of  their 
resistance. 

In  the  abstract  chemical  sense,  reproduc- 
tion of  a  contagion  depends  upon  the  pre- 
sence of  two  substances,  one  of  which  be- 
comes completely  decomposed,  but  commu- 
nicates its  own  state  of  transformation  to 
the  second.  The  second  substance  thus 

of  sulphuric  acid,  prove  that  peculiar  substances 
arc  contained  in  the  blood  of  different  individuals ; 
the  blood  of  a  man  of  a  fair  complexion  and  that 
of  a  man  of  dark  complexion  were  found  to  yield 
different  odours  ;  the  blood  of  animals  also  dif- 
fered in  this  respect  very  perceptibly  from  that  of 


thrown  into  a  state  of  decomposition  is  the 
newly-formed  contagion. 

The  second  substance  must  have  been 
originally  a  constituent  of  the  blood :  the 
first  may  be  a  body  accidentally  present; 
but  it  may  also  be  a  matter  necessary  to  life. 
If  both  be  constituents  indispensable  for  the 
support  of  the  vital  functions  of  certain 
principal  organs,  death  is  the  consequence 
of  their  transformation.  But  if  the  abronoe 
of  the  one  substance  which  was  a  constitu- 
ent of  the  blood  do  not  cause  an  immediate 
cessation  of  the  functions  of  the  most  im- 
portant organs,  if  they  continue  in  their 
action,  although  in  an  abnormal  condition, 
convalescence  ensues.  In  this  case  the  pro- 
ducts of  the  transformations  still  existing  in 
the  blood  are  used  for  assimilation  and  at 
this  period  secretions  of  a  peculiar  nature 
are  produced. 

When  the  constituent  removed  from  the 
blood  is  a  product  of  an  unnatural  manner 
of  living,  or  when  its  formation  takes  place 
only  at  a  certain  age,  the  susceptibility  of 
contagion  ceases  upon  its  disappearance. 

The  effects  of  vaccine  matter  indicate  that 
an  accidental  constitution  of  the  blood  is 
destroyed  by  a  peculiar  process  of  decom- 
position, which  does  not  affect  the  other 
constituents  of  the  circulating  fluid. 

If  the  manner  in  which  the  precipitated 
yeast  of  Bavarian  beer  acts  (page  107)  be 
called  to  mind,  the  modus  operandi  of  vac- 
cine lymph  can  scarcely  be  matter  of  doubt. 

Both  the  kind  of  yeast  here  referred  to 
and  the  ordinary  ferment  are  formed  from 
gluten,  just  as  the  vaccine  virus  and  the 
matter  of  small  pox  are  produced  from  the 
blood.  Ordinary  yeast  and  the  virus  of 
human  small-pox,  however,  effect  a  violent 
tumultuous  transformation,  the  former  in 
vegetable  juices,  the  latter  in  blood,  in  both 
of  which  fluids  respectively  their  constitu- 
ents are  contained,  and  they  are  reproduced 
from  these  fluids  with  all  their  charac- 
teristic properties.  The  precipitated  yeast 
of  Bavarian  beer  on  the  other  hand  acts  en- 
tirely upon  the  sugar  of  the  fermenting 
liquid  and  occasions  a  very  protracted  de- 
composition of  it,  in  which  the  gluten  which 
is  also  present  takes  no  part.  But  the  air 
exercises  an  influence  upon  the  latter  sub- 
stance, and  causes  it  to  alssume  a  new  form 
and  nature,  in  consequence  of  which  this 
kind  of  yeast  also  is  reproduced. 

The  action  of  the  virus  of  cow-pox  is 
analogous  to  that  of  the  low  yeast;  it  com- 
municates its  own  state  of  decomposition  to 
a  matter  in  the  blood,  and  from  a  second 
matter  is  itself  regenerated,  but  by  a  totally 
different  mode  of*  decomposition;  the  pro- 
duct possesses  the  mild  form,  and  all  the 
properties  of  the  lymph  of  cow-pox. 

The  susceptibility  of  infection  by  the  virus 
of  human  small-pox  must  cease  after  vacci- 
nation, for  the  substance  to  the  presence  of 
which  this  susceptibility  is  owing  has  been 
remoi  ed  from  the  body  by  a  peculiar  pro- 
cess of  decomposition  artificially  excited. 


POISONS,   CONTAGIONS,   MIASMS. 


127 


But  this  substance  may  be  again  generated 
in  the  same  individual,  so  thai  he  may  again 
become  liable  to  contagion,  and  a  second  or 
a  third  vaccination  will  again  remove  the 
peculiar  substance  from  the  system. 

Chemical  actions  are  propagated  in  no 
organs  so  easily  as  in  the  lungs,  and  it  is 
well  known  that  diseases  of  the  lungs  are 
above  all  others  frequent  and  dangerous. 

If  it  is  assumed  that  chemical  action  and 
the  vital  principle  mutually  balance  each 
other  in  the  blood,  it  must  farther  be  sup- 
posed that  the  chemical  powers  will  have 
a  certain  degree  of  preponderance  in  the 
lungs,  where  the  air  and  blood  are  in  imme- 
diate contact;  for  these  organs  are  fitted  by 
nature  to  favour  chemical  action ;  they  offer 
no  resistance  to  the  changes  experienced  by 
the  venous  blood. 

The  contact  of  air  with  venous  blood  is 
limited  to  a  very  short  period  of  time  by  the 
motion  of  the  heart,  and  any  change  be- 
yond a  determinate  point  is,  in  a  certain 
degree,  prevented  by  the  rapid  removal  of 
the  blood  which  has  become  a-rterialised. 
Any  disturbance  in  the  functions  of  the 
heart,  and  any  chemical  action  from  with- 
out, even  though  weak,  occasions  a  change 
in  the  process  of  respiration.  Solid  sub- 
stances also,  such  as  dust  from  vegetable, 
animal,  or  inorganic  bodies,  act  in  the  same 
way  as  they  do  in  a  saturated  solution  of  a 
salt  in  the  act  of  crystallization,  that  is,  they 
occasion  a  deposition  of  solid  matters  from 
the  blood,  by  which  the  action  of  the  air 
upon  the  latter  is  altered  or  prevented. 

When  gaseous  and  decomposing  sub- 
stances, or  those  which  exercise  a  chemical 
action,  such  as  sulphuretted  hydrogen  and 
carbonic  acid,  obtain  access  to  the  lungs, 
they  meet  with  less  resistance  in  this"  organ 
than  in  any  other.  The  chemical  process 
of  slow  combustion  in  the  lungs  is  accele- 
rated by  all  substances  in  a  state  of  decay 
or  putrefaction,  by  ammonia  and  alkalies ; 
but  it  is  retarded  by  empyreumatic  sub- 
stances, volatile  oils,  and  acids.  Sulphu- 
retted hydrogen  produces  immediate  decom- 
position of  the  blood,  and  sulphurous  acid 
combines  with  the  substance  of  the  tissues, 
the  cells,  and  membranes. 

When  the  process  of  respiration  is  modi- 
fied by  contact  with  a  matter  in  the  pro- 
gress of  decay,  when  this  matter  commu- 
nicates the  state  of  decomposition,  of  which 
it  is  the  subject,  to  the  blood,  disease  is  pro- 
duced. 

If  the  matter  undergoing  decomposition 
is  the  product  of  a  disease,  it  is  called  con- 
tagion; but  if  it  is  a  product  of  the  decay 
or  putrefaction  of  animal  and  vegetable 
substances,  or  if  it  acts  by  its  chemical  pro- 
perties, (not  by  the  state  in  which  it  is,)  and 
therefore  enters  into  combination  with  parts 
of  the  body,  or  causes  their  decomposition, 
it  is  termed  miasm. 

Gaseous  contagious  matter  is  a  miasm 
emitted  from  blood,  and  capable  oJ  gene- 
rating itself  again  in  blood 


I      But  miasm,  properly  so   called,  causes 
disease  without  being  itself  reproduced. 

All  the  observations  hitherto  made  upon 
gaseous  contagious  matters  prove,  that  they 
also  are  substances  in  a  state  of  decompo- 
sition. When  vessels  filled  with  ice  are 
placed  in  air  impregnated  with  gaseous  con- 
tagious matter,  their  outer  surfaces  become 
covered  with  water  containing  a  certain 
quantity  of  this  matter  in  solution.  This 
water  soon  becomes  turbid,  and  in  common 
language  putrefies,  or,  to  describe  the  chanp-e 
more  correctly,  the  state  of  decomposition 
of  the  dissolved  contagious  matter  is  com- 
pleted in  the  water. 

All  gases  emitted  from  putrefying  animal 
and  vegetable  substances  in  processes  of 
disease,  generally  possess  a  peculiar  nau- 
seous offensive  smell,  a  circumstance  which, 
in  most  cases,  proves  the  presence  of  a  body 
in  a  state  of  decomposition.  Smell  itself 
may  in  many  cases  be  considered  as  a  re- 
action of  the  nerves  of  smell,  or  as  a  resist- 
ance offered  by  the  vital  powers  to  chemical 
action. 

Many  metals  emit  a  peculiar  odour  when 
rubbed,  but  this  is  the  case  with  none  of 
the  precious  metals, — those  which  suffer  no 
change  when  exposed  to  air  and  moisture. 
Arsenic,  phosphorus,  musk,  the  oils  of  lin- 
seed, lemons,  turpentine,  rue,  and  pepper- 
mint, possess  an  odour  only  when  they  are 
in  the  act  of  eremacausis  (oxidation  at  com- 
mon temperatures.) 

The  odour  of  gaseous  contagious  matters 
is  owing  to  the  same  cause ;  but  it  is  also 
generally  accompanied  by  ammonia,  which 
may  be  considered  in  many  cases  as  the 
means  through  which  the  contagious  matter 
receives  a  gaseous  form,  just  as  it  is  the 
means  of  causing  the  smell  of  innumerable 
substances  of  little  volatility,  and  of  many 
which  have  no  odour.  (Robiquet.)* 

Ammonia  is  very  generally  produced  in 
cases  of  disease;  it  is  always  emitted  in 
those  in  which  contagion  is  generated,  and 
is  an  invariable  pioductof  the  decomposition 
of  animal  matter.  The  presence  of  ammo- 
nia in  the  air  of  chambers  in  which  diseased 
patients  lie,  particularly  of  those  afflicted 
with  a  contagious  disease,  may  be  readily 
detected;  for  the  moisture  condensed  by  ice 
in  the  manner  just  described,  produces  a 
white  precipitate  in  a  solution  of  corrosive 
sublimate,  just  as  a  solution  of  ammonia 
does.  The  ammoniacal  salts  also,  which 
are  obtained  by  the  evaporation  of  rain- 
water after  an  acid  has  been  added,  when 
treated  with  lime  so  as  to  set  free  their  am- 
monia, emit  an  odour  most  closely  resem- 
bling that  of  corpses,  or  the  peculiar  smell 
of  dunghills. 

By  evaporating  acids  in  air  containing 
gaseous  contagions,  the  ammonia  is  neu- 
tralised, and  we  thus  prevent  further  de- 
composition, and  destroy  the  power  of  the 
contagion,  that  is,  its  state  of  chemical 

*  Ann.  de  Chim.  et  de  Phys.  XV.  27. 


128 


AGRICULTURAL   CHEMISTRY. 


change.  Muriatic  and  acetic  acids,  and  in 
several  cases  nitric  acid,  are  to  be  preferred 
for  this  purpose  before  all  others.  Chlorine 
also  is  a  substance  which  destroys  ammonia 
and  organic  bodies  with  much  facility ;  but 
it  exerts  such  ao  injurious  and  prejudicial 
influence  upon  the  lungs,  that  it  may  be 
classed  amongst  the  most  poisonous  bodies 
known,  and  should  never  be  employed  in 
places  in  which  men  breathe. 

Carbonic  acid  and  sulphuretted  hydrogen, 
which  are  frequently  evolved  from  the  earth 
in  cellars,  mines,  wells,  sewers,  and  other 
places,  are  amongst  the  most  pernicious  mi- 
asms.  The  former  may  be  removed  from 
the  air  by  alkalies,  the  latter,  by  burning 
sulphur,  (sulphurous  acid,)  or  by  the  evapo- 
ration of  nitric  acid. 

The  characters  of  many  organic  com- 
pounds are  well  worthy  of  the  attention  and 
study  both  of  physiologists  and  pathologists, 
more  especially  in  relation  to  the  mode  of 
action  of  medicines  and  poisons. 

Several  of  such  compounds  are  known, 
which  to  all  appearance  are  quite  indifferent 
substances,  and  yet  cannot  be  brought  into 
contact  with  one  another  in  water  without 
suffering  a  complete  transformation.  All 
substances  which  thus  suffer  a  mutual  de- 
composition, possess  complex  atoms ;  they 
belong  to  the  highest  order  of  chemical  com- 
pounds. For  example,  amygdalin,  a  con- 
stituent of  bitter  almonds,  is  a  perfectly  neu- 
tral body,  of  a  slightly  bitter  taste,  and  very 
easily  soluble  in  water.  But  when  it  is  in- 
troduced into  a  watery  solution  of  synaptas, 
(a  constituent  of  sweet  almonds,)  it  disap- 
pears completely  without  the  disengagement 
of  any  gas,  and  the  water  is  found  to  con- 
tain free  hydrocyanic  acid,  hydruret  of  ben- 
zule  (oil  of  bitter  almonds,)  a  peculiar  acid 
and  sugar,  all  substances  of  which  merely 
the  elements  existed  in  the  amygdalin.  The 
same  decomposition  is  effected  when  bitter 
almonds,  which  contain  the  same  white 
matter  as  the  sweet,  are  rubbed  into  a  pow- 
der and  moistened  with  water.  Hence  it 
happens  that  bitter  almonds  pounded  and 
digested  in  alcohol,  yield  no  oil  of  bitter  al- 
monds containing  hydrocyanic  acid,  by  dis- 
tillation with  water ;  for  the  substance  which 
occasions  the  formation  of  those  volatile  sub- 
stances, is  dissolved  by  alcohol  without 
change,  and  is  therefore  extracted  from  the 
pounded  almonds.  Pounded  bitter  almonds 
contain  no  amygdalin,  also,  after  having 
been  moistened  with  water,  for  that  sub- 
stance is  completely  decomposed  when  they 
are  thus  treated. 

No  volatile  compounds  can  be  detected  by 
their  smell  in  the  seeds  of  the  Sinapis  alba 
and  S.  rug-ra.  A  fixed  oil  of  a  mild  taste  is 
obtained  from  them  by  pressure,  but  no  trace 
of  a  volatile  substance.  If,  however,  the 
seeds  are  rubbed  to  a  fine  powder,  and  sub- 
jected to  distillation  with  water,  a  volatile 
oil  of  a  very  pungent  taste  and  smell  passes 
over  along  with  the  steam.  But  if,  on  the 
Contrary,  the  seeds  are  treated  with  ilcohol 


previously  to  their  distillation  w/th  water,  tne 
residue  does  not  yield  a  volatile  oil.  The 
alcohol  contains  a  crystalline  body  called 
sinapin,  and  several  other  bodies.  Those  do 
not  possess  the  characteristic  pungency  of 
the  oil,  but  it  is  by  the  contact  of  them  with 
water,  and  with  the  albuminous  constituents 
of  the  seeds,  that  the  volatile  oil  is  formed. 

Thus  bodies  regarded  as  absolutely  indif- 
ferent in  inorganic  chemistry,  on  account  of 
their  possessing  no  prominent  chemical 
characters,  when  placed  in  contact  with  one 
another,  mutually  decompose  each  other. 
Their  constituents  arrange  themselves  in  a 
peculiar  manner,  so  as  to  form  new  com- 
binations j  a  complex  atom  dividing  into  two 
or  more  atoms  of  less  complex  constitution, 
in  consequence  of  a  mere  disturbance  in  the 
attraction  of  their  elements. 

The  white  constituents  of  the  almonds 
and  mustard,  which  resemble  coagulated  al- 
bumen, must  be  in  a  peculiar  state  in  order 
to  exert  their  action  upon  amygdalin,  and 
upon  those  constituents  of  mustard  from 
which  the  volatile  pungent  oil  is  produced. 
If  almonds,  after  being  blanched  and 
pounded,  are  thrown  into  boiling  water,  or 
treated  with  hot  alcohol,  with  mineral  acids, 
or  with  salts  of  mercury,  their  power  to 
effect  a  decomposition  in  amygdalin  is  com- 
pletely destroyed.  Synaptas  is  an  azotised 
body  which  cannot  be  preserved  when  dis- 
solved in  water.  Its  solution  becomes 
rapidly  turbid,  deposits  a  white  precipitate, 
and  acquires  the  offensive  smell  of  putrefy- 
ing bodies. 

It  is  exceedingly  pwobable  that  the  pecu- 
liar state  of  transposition  into  which  the  ele- 
ments of  synaptas  are  thrown  when  dis- 
solved, in  water,  may  be  the  cause  of  the 
decomposition  of  amygdalin,  and  formation 
of  the  new  products  arising  from  it.  The 
action  of  synaptas  in  this  respect  is  very 
similar  to  that  of  rennet  upon  sugar. 

Malt,  and  the  germinating  seeds  of  corn 
in  general,  contain  a  substance  called  dias- 
tase, which  is  formed  from  the  gluten  con- 
tained in  them,  and  cannot  be  brought  in 
contact  with  starch  and  water,  without  effect- 
ing a  change  in  the  starch. 

When  bruised  malt  is  strewed  upon  warm 
starch  made  into  a  paste  with  water,  the 
paste  after  a  few  minutes  becomes  quite 
liquid,  and  the  water  is  found  to  contain,  in 
place  of  starch,  a  substance  in  many  respects 
similar  to  gum.  But  when  more  malt  is 
added  and  the  heat  longer  continued,  the 
liquid  acquires  a  sweet  taste,  and  all  the 
starch  is  found  to  be  converted  into  sugar  of 
srrapes. 

The  elements  of  diastase  have  at  the  same 
time  arranged  themselves  mto  new  combina- 
tions. 

The  conversion  of  the  starch  contained  in 
food  into  sugar  of  grapes  in  diabetes  indi- 
cates that  amongst  the  constituents  of  some 
one  organ  of  the  body  a  substance  or  sub- 
stances exist  in  a  state  of  chemical  acfion, 

which  the  vital  principle  of  the  diseased 


POISONS,  CONTAGIONS,  MIASMS. 


129 


organ  opposes  no  resistance.  The  compo- 
nent parts  of  the  organ  must  suffer  changes 
simultaneously  with  the  starch,  so  that  the 
more  starch  is  furnished  to  it,  the  more  ener- 
getic and  intense  the  disease  must  become ; 
while  if  only  food  which  is  incapable  of 
suffering  such  transformations  from  the 
same  cause  is  supplied,  and  the  vital  energy 
is  strengthened  by  stimulant  remedies  and 
nourishment,  the  chemical  action  may  finally 
be  subdued,  or,  in  other  words,  the  disease 
cured. 

The  conversion  of  starch  into  sugar  may 
also  be  effected  by  pure  gluten,  and  by  dilute 
mineral  acids. 

From  all  the  preceding  facts,  we  see  that 
very  various  transpositions,  and  changes  of 
composition  and  properties,  may  be  pro- 
duced in  complex  organic  molecules,  by 
every  cause  which  occasions  a  disturbance 
in  the  attraction  of  their  elements. 

When  moist  copper  is  exposed  to  air  con- 
taining carbonic  acid,  the  contact  of  this 
acid  increases  the  affinity  of  the  metal  for 
the  oxygen  of  the  air  in  so  great  a  degree 
that  they  combine,  and  the  surface  of  the 
copper  becomes  covered  with  green  carbo- 
nate of  copper.  Two  bodies,  which  pos- 
sess the  power  of  combining  together,  as- 
sume, however,  opposite  electric  conditions 
at  the  moment  at  which  they  come  in 
contact. 

When  copper  is  placed  in  contact  with 
iron,  a  peculiar  electric  condition  is  excited, 
in  consequence  of  which  the  property  of 
the  copper  to  unite  with  oxygen  is  destroyed, 
and  the  metal  remains  quite  bright. 

When  formate  of  ammonia  is  exposed  to 
a  temperature  of  388°  F.  (180°  C.)  the  in- 
tensity and  direction  of  the  chemical  force 
undergo  a  change,  and  the  conditions  under 
which  the  elements  of  this  compound  are 
enabled  to  remain  in  the  same  form  ceases 
to  be  present.  The  elements,  therefore,  ar- 
range themselves  in  a  new  form;  hydro- 
cyanic acid  and  water  being  tne  result  of 
the  change. 

Mechanical  motion,  friction,  or  agitation, 
is  sufficient  to  cause  a  new  disposition  of 
the  constituents  of  fulminating  silver  and 
mercury,  that  is,  to  effect  another  arrange- 
ment of  their  elements,  in  consequence  of 
which,  new  compounds  are  formed. 

We  know  that  electricity  and  heat  possess 
a  decided  influence  upon  the  exercise  of 
chemical  affinity;  and  that  the  attractions 
of  substances  for  one  another  are  subordi- 
nate to  numerous  causes  which  change  the 
condition  of  these  substances,  by  altering 
the  direction  of  their  attractions.  In  the 
same  manner,  therefore,  the  exercise  of 
chemical  powers  in  the  living  organism  is 
dependent  upon  the  vital  principle. 

The  power  of  elements  to  unite  together, 
and  to  form  peculiar  compounds,  which  are 
generated  in  animals  and  vegetables,  is 
chemical  affinity ;  but  the  cause  by  which 
they  are  prevented  from  arranging  them- 
selves according  to  the  degrees  of  their  natu- 


ral attractions — the  cause,  therefore,  by 
which  they  are  made  to  assume  their  pecu- 
liar order  and  form  in  the  body — is  the  vital 
principle. 

After  the  removal  of  the  cause  which 
forced  their  union — that  is,  after  the  extinc- 
tion of  life — most  organic  atoms  retain  their 
condition,  form,  and  nature,  only  by  a  vis  in- 
ertia ;  for  a  great  law  of  nature  proves  that 
matter  does  not  possess  the  power  of  spon- 
taneous action.  A  body  in  motion  loses  its 
motion  only  when  a  resistance  is  opposed  to 
it ;  and  a  body  at  rest  cannot  be  put  in  mo- 
tion, or  into  any  action  whatever,  without 
the  operation  of  some  exterior  cause. 

The  same  numerous  causes  which  are 
opposed  to  the  formation  of  complex  organic 
molecules,  under  ordinary  circumstances, 
occasion  their  decomposition  and  transform- 
ations when  the  only  antagonist  power,  the 
vital  principle,  no  longer  counteracts  the  in. . 
fluence  of  those  causes.  Contact  with  air 
and  the  most  feeble  chemical  action  now 
effect  changes  in  the  complex  molecules ; 
even  the  presence  of  any  body  the  particles 
of  which  are  undergoing  motion  or  transpo- 
sition, is  often  sufficient  to  destroy  their  state 
of  rest,  and  to  disturb  the  statical  equilibrium 
in  the  attractions  of  their  constituent  ele- 
ments. An  immediate  consequence  of  this 
is  that  they  arrange  themselves  according  to 
the  different  degrees  of  their  mutual  attrac- 
tions, and  that  new  compounds  are  formed 
in  which  chemical  affinity  has  the  ascend- 
ency, and  opposes  any  further  change, 
while  the  conditions  under  which  these 
compounds  were  formed  remained  unaltered. 


TABLES: 

SHOWING    THE    PROPORTION    BETWEEN    THE 

HESSIAN  AND  ENGLISH  STANDARD  OF 

WEIGHTS  AND  MEASURES. 

IN  general  all  the  weights  and  measures 
employed  in  this  edition  are  those  of  the 
English  standard.  In  a  few  cases  only,  the 
Hessian  weights  and  measures  have  been 
retained.  In  these  the  numbers  do  not  re- 
present absolute  quantities,  but  are  merely 
intended  to  denote  a  proportion  to  other 
numbers.  This  has  been  done  to  avoid  any 
unnecessary  intricacy  in  the  calculations, 
and  to  present  whole  numbers  to  the  reader, 
without  distracting  his  attention  by  decimal 
parts.  For  those,  however,  who  wish  to  be 
acquainted  with  the  exact  English  quanti- 
ties, a  table  is  given  below. 

1  Ib.  English  is  equal  to  0-90719  Ibs.  Hes- 
sian, hence,  about  one-tenth  less  than  the 
latter. 

1  Ib.  Hessian  is  equal  to      T102  Ibs.  English. 

2  Ibs.  Hessian  are  equal  to  2'204  " 

3 3-306  " 

4         -        -        -        -        4-409 

5 5-511  " 

6         ....  6-612  " 

7 7-716  " 

8  -  8-818  " 


130 


AGRICULTURAL   CHEMISTRY. 


9  Ibs.  Hessian  are  equal  to  9'92  Ibs.  Eng 
10        •        -        .        -      11-02 
20   22-04 
30        ....      33-06 

lish. 

t 

fig 
of 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 

( 

of 
En 
eqi 

50 
fiO    . 

.      55-11 
•        -  66*12 

70 

-      77-16 

90 
100            . 
200 
300 
400 
500    -         - 
600         •• 
700    ... 
800 
900    . 
1000 

.      99-29 
110-2 
.    220-4 
330-6 
.    440-9 
551-1 
.    661-2 
771-6 
.    881-8 
992-0 
.  1102-0                • 

SQUARE  FEET. 

The  Hessian  acre  is  equal  to  40,000  Hes- 
eian  square  feet,  or  26,91 1  English  square 
feet;  1  English  square  foot  being  equal  to 
1-4864  Hessian.  The  following  is  a  table 
to  save  the  trouble  of  calculation.  The 
table  is  only  stated  to  the  figure  10,  but  by 
removing  the  decimal  point  one  or  two 


figures,  the  whole  series  given  in  the  cas4 
of  the  pounds  will  also  be  obtained. 
1  Sq.  foot  Hessian  is  equal  to  0'6 12  Sq.  foot  Eng. 


2-018 
2-691 
3-363 
4-036 
4-709 
5-382 
6-054 
6-727 


feet 


CUBIC  FEET. 

One  English  cubic  foot  contains  1-81218 
of  a  Hessian  cubic  foot;  the  Hessian  and 
English  cubic  inch  may  be  considered  as 

ual,  one  English  cubic  inch  containing 
1-048715  Hessian  cubic  inch. 

1  cub.  foot  Hessian  is  eq.  to  0*551  cub.  foot  Eng. 

2  feet  -        -        -    1-103 


3          ....  1-665 

4 2-207 

5          ....  2-759 

6 3-311 

7  3-863 

8 4-415 

9          ....  4-966 

10 5-518 


feet 


THE  END, 


INDEX. 


A. 

Absorption,  by  roots,  37 — Of  salts,  39. 

Acid,  acetic,  emitted  by  plants,  51 — transforma- 
tion of,  92 — formation  of,  100,  102 — Boracic, 
42 — Carbonic,  10 — contained  in  the  atmo- 
sphere, 11 — decomposed  by  plants,  16 — from 
respiration,  16 — why  necessary  to  plants,  36 
— Cyanic,  transformation  of,  94 — Formic,  25, 
26,  88 — Hippuric,  33 — Humic,  12 — proper- 
ties of,  13 — Hydrocyanic,  25,  88 — Kinic,  39 — 
Lactic,  64 — production  of,  98 — Meconic,  39 — 
Melanic,  99 — Nitric,  source  of,  32 — Phosphoric, 
in  ashes  of  plants,  53 — Rocellic,  in  plants,  37 
— Succinic,  112 — Sulphuric,  action  of,  on  soils, 
70,  84 — Tartaric,  in  grapes,  37. 

Acids,  action  of  upon  sugar,  92 — Arrest  decay, 
1 1 1 — Capacity  for  saturation,  36 — Organic,  in 
plants,  11,  36 — when  formed,  18. 

Affinity,  action  of,  25 — Chemical,  examples  of, 
88— Weak,  example  of,  88. 

Agave  Americana,  absorbs  oxygen,  18. 

Agriculture,  in  China,  65— Object  of,  34,  49,  57 
— how  attained,  49 — Its  importance,  49 — A 
principle  in,  63. 

Air,  access  of,  favoured,  27 — Ammonia  in,  11, 32 
— Carbonic  acid  in,  15 — Effect  of  upon  juices, 
100 — on  soils,  56 — Improved  by  plants,  17 — 
Necessary  to  plants,  44. 

Albumen,  33. 

Alcohol,  effect  of  heat  on,  93— Exhaled,  25— 
Products  of  its  oxidation,  99 — From  sugar,  95. 

Aldehyde,  99. 

Alkalies,  from  granitic  soils,  40 — Presence  of,  in- 
dicated, 72 — Promote  decay  in  wood,  111 — 
Quantity  in  aluminous  minerals,  50. 

Alkaline  bases,  in  plants,  on  what  their  existence 
depends,  38 — Salts  in  plants,  sources  of,  51 — 
contained  in  fertile  soils,  52. 

Alloxan,  108. 

Alloxantin,  108. 

Alumina,  in  fertile  soils,  49 — Its  influence  on 
vegetation,  49. 

Amber,  origin  of,  112. 

Ammonia,  carbonate  of,  from  wine,  64 — how  fixed, 
64 — Cause  of  nitrification,  103 — Changes  co- 
lours, 30 — Condensed  by  charcoal,  35 — Con- 
version of,  into  nitric  acid,  103 — Early  exist- 
ence of,  42 — Fixed  by  gypsum,  64 — From 
animals,  58 — Contained  in  beet-root,  &c.,  32 
— maple  juice,  33 — stables,  &c.,  64 — Fur- 
nishes nitrogen,  36 — Loss  from  evaporation, 
34 — Produced  by  animal  organism,  42 — Pro- 
duct of  decay,  30 — disease,  129 — Properties 
of,  31 — Quantity  absorbed  by  charcoal,  35 — 
by  decayed  wood,  35 — In  rain-water,  31 — Se- 
parated from  soils  by  rain,  35 — In  snow  water, 
32 — Solubility  of,  31 — Transformation  of,  30. 

Amylin,  its  effect,  26. 

Analysis  of  decayed  wood,  111 — Of  fire-damp, 
115— Of  guano,  67— Of  lentils,  54— Of  oak- 


wood,  110— Of  night-soil,  60— Of  salt  waU 
43— Of  soils,  73— 113— Of  wood  coal,  1U 

Animal  food,  preservation  of,  101 — Life,  con- 
nexion of,  with  plants,  9 — Bodies,  products  of 
decay,  30. 

Animals,  excrements  of,  18,  63. 

Annual  plants,  how  nourished,  46. 

Anthoxanthum  odoratum,  acid  in,  33. 

Anthracite,  115. 

Antidotes  to  poisons,  118. 

Apatite,  53. 

Arable  land,  50. 

Aromatics,  their  influence  on  fermentation,  !  05. 

Argillaceous  earth,  its  origin,  50. 

Arragonite,  transformation  of,  90. 

Argenious  acid,  action  of,  118. 

Ashes,  as  manure,  67 — Comparative  value  of,  61 
—Of  fire-wood,  38— Of  pine  trees,  37— Of 
plants,  origin  of  salt  in,  43 — Importance  of  ex- 
amination of,  38 — Of  wheat,  53 — used  as  a 
manure,  72 — Of  bones,  62 — Of  peat,  62 — Of 
coals,  67. 

Assimilation,  of  carbon,  12,  23 — Of  carbonic  acid, 
and  ammonia,  45 — Of  hydrogen,  28,  29 — Of 
nitrogen,  30,  36 — Its  power,  48. 

Atmosphere,  ammonia  in,  11,  32 — Composition 
of,  11 — How  maintained,  16 — Composition  is 
invariable,  15 — Carbonic  acid  in  the,  11 — Mo- 
tion of,  17. 

Atoms,  motions  of  89 — Permanence  in  position 
of,  89. 

Attraction,  powerful,  overcome,  94. 

Azotised  matter  in  juices  of  plants,  47 — Sub- 
stances, combustion  of,  102. 

B. 

Bamboo,  silica  in,  58. 

Bark  of  trees,  products  in,  18. 

Barley,  analysis  of,  53. 

Barruel,  his  experiments  on  the  blood,  125. 

Base,  what,  36. 

Bases,  alkaline,  in  plants,  on  what  their  existence 
depends,  38 — Organic,  11 — Oxygen  contained 
in,  36— In  plants,  37— Substitution  of,  37. 

Beans,  alkalies  in,  54 — Nutritive  power  of,  54 

Becquerrel,  experiments  of,  51. 

Beech,  ashes  of,  30. 

Beer,  107— 109— Bavarian,  107— Varieties  of. 
106. 

Beet-root  sugar,  14 — Ammonia  from,  32 — From 
sandy  soils,  47. 

Benignant  disease,  126. 

Benzoic  acid,  formed,  33. 

Birch  tree,  ammonia  from,  33. 

Blood,  its  office,  46 — Action  of  chemical  agents 
upon,  123 — Its  feeble  resistance  to  exterior  in- 
fluences, 123 — Organic  salts  in,  116-  Its  cha- 
racter, 120. 

Blossoms,  when  produced,  24 — Increased,  45- 
Removal  of,  from  potatoes,  46. 


132 


INDEX. 


Bones,  dust  of,  62 — Durability  of,  68 — Gelatine 

in,  68 — Use  in  compost,  72. 
Bouquet  of  wines,  105. 
Boracic  acid,  41. 

Botanists,  neglect  of  chemistry  by,  20. 
Brandy,  from  corn,  105— Oil  of,  105. 
Brazil,  wheat  in,  52. 
Brown  coal,  113. 
Buckwheat,  ashes  of,  54. 
Bulbs,  how  nourished,  27. 

C. 

Calcareous  spar,  90. 

Calpium,  fluoride  of,  53 — Chloride  of,  64. 

Calculous  disorders,  26. 

Calico  printing,  use  of  cow-dung  in,  63. 

Caoutchouc,  in  plants,  27. 

Carbon,  10 — Afforded  to  the  soil  by  plants,  27 — 
Assimilation  of,  12-23 — Combination  of,  with 
Oxygen,  10 — Of  decaying  substances  seldom 
affected  by  oxygen,  111 — Derived  from  air,  16 
— In  decaying  wood,  1 1 1 — In  decaying  woody 
fibre,  111 — In  sea-water,  16 — Oxide  of,  formed, 
92 — Quantity  in  grain,  14 — in  land,  14 — in 
straw,  14 — Restored  to  the  soil,  27 — Received 
by  leaves,  16 — Its  affinity  for  oxygen,  100. 

Carbonate  of  ammonia  decomposed  by  gypsum, 
34 — Of  lime  in  caverns  and  vaults,  43. 

Carbonic  acid  in  the  atmosphere,  11 — Changes 
in  the  leaves,  48 — Decomposed  by  plants,  16 — 
Emission  of,  at  night,  18 — Evaporation  of,  20 
— Evolution  from  decaying  bodies,  100 — From 
decaying  plants,  29 — excrements,  34 — humus, 
23 — respiration,  25 — springs,  29 — woody  fibre, 
23 — Increase  of,  prevented,  16 — Influence  of 
light  on  its  decomposition,  19. 

Carburetted  hydrogen  with  coal,  115. 

Caverns,  stalactites  in,  43. 

Charcoal  condenses  ammonia,  35 — Experiments 
of  Lukas  on,  84 — May  replace  humus,  27 — 
Theory  of  its  action,  27 — Promotes  growth  of 
plants,  84. 

Chemical  effects  of  light,  48 — Forces  can  replace 
the  vital  principle,  26 — Processes  in  nutrition 
of  vegetables,  9 — Transformations,  25,  87. 

Chemistry,  definition  of,  9 — Organic,  what  is,  9 
— Neglected  by  botanists,  20 ;  and  physiolo- 
gists, 20. 

China,  its  agriculture,  65 — Collection  and  use  of 
manure  in,  65. 

Chloride  of  calcium,  64 — Of  nitrogen,  88— Of 
potassium,  its  effect,  39 — Of  sodium,  its  vola- 
tility, 42. 

Clay,  burned,  advantages  of,  as  a  manure,  35. 

Clays,  potash  in,  50. 

Clay  slate,  53. 

Coal,  formation  of,  113 — Inflammable  gases  from, 
1 1 5 — Origin  of  substances  in,  1 12 — Of  humus, 
12,  44— Wood  or  brown,  113. 

Colours  of  flowers,  33. 

Combustion  at  low  temperatures,  100 — Of  de- 
cayed wood,  112 — Induction  of,  102 — Re- 
moves oxygen,  16 — Spontaneous,  94. 

Compost  manure,  72. 

Concretions  from  horses,  53. 

Constituents  of  plants,  10. 

Contagions,  reproduction  of,  on  what  dependent, 

121 — Susceptibility  to,  how  occasioned,  125. 
Contagions,  how  produced,  121 — Propagation  of, 

124. 
Contagious  matters,  action  of,  124,  122,  129— 


Their  effects  explained,  121 — Life  in,  disproved 

121 — Reproduction  of,  121. 
Copper  alloy,  its  action,  on  sulphuric  acid,  88. 
3orn,  how  cultivated  in  Italy,  52 — Phosphate  of 

magnesia  in,  53. 
3orn  brandy,  105. 
Corrosive  sublimate,  action  of,  118. 
3ow,  excrements  of  the,  41,  59,  60 — Variable  in 

value,  60 — Urine  of  the,  60 ;  rich  in  potash, 

41. 

Cow-pox,  action  of  virus  of,  127. 
Urops,  rotation  of,  54 — Favorable  effects  of,  55— 

Principles  regulating,  59. 
Cultivation,  its  benefits,  17 — Different  methods  of, 

49_Object  of,  49. 
Culture,  art  of,  43— Of  plants,  principles  of  the, 

49. 

Cyanic  acid,  transformation  of,  94. 
Cyanogen,  combustion  of,  102 — Transformation 

of,  94. 

D. 

Davis,  his  account  of  Chinese  manure,  65. 

Death  from  nutritious  substances,  21 — The  source 
of  life,  36. 

Decandolle,  his  theory  of  excretion,  55 — Dif- 
ference of  his  views  and  those  of  Macaire- 
Princep,  56. 

Decay,  98 — A  source  of  ammonia,  30 — Of  wood, 
109 — Of  plants  restores  oxygen,  29 — and  pu- 
trefaction, 88. 

Decomposition,  24,  87 — Organic,  chemical,  88. 

Dextrine,  21. 

Diamond,  its  origin,  112. 

Diastase,  46 — Contains  nitrogen,  46. 

Disease,  how  excited,  120. 

Dog,  excrement  of  the,  59. 

Dung  hills,  liquid  from,  64 — Reservoirs,  64. 

E. 

Ebony  wood,  oxygen  and  hydrogen  in,  19. 

Effete  matters  separated,  24. 

Elements  of  plants,  10 — Not  generated  by  or- 
gans, 21. 

Elphinstone,  Sir  Howard,  on  soda-ash,  as  a  ma- 
nure, 69. 

Equilibrium  of  attractions  disturbed,  92. 

Equisetacse  contain  silica,  58. 

Eremacausis,  98 — Analogous  to  putrefaction,  130 
—Arrested,  98— Definition  of,  98— Necessary 
to  nitrification,  102 — Of  bodies  containing  ni- 
trogen, 102 — Of  bodies  destitute  of  nitrogen, 
100. 

Ether,  oenanthic,  105. 

Excrementitious  matter,  production  of,  illus- 
trated, 25. 

Excrement,  animal,  its  chemical  nature,  59 — Of 
the  dog,  cow,  &c.,  59 — Influence  of,  as  ma- 
nure, 61. 

Excrements  of  plants,  55 — Conversion  of,  inta 
humus,  13 — Of  man,  amount  of,  65 — Value  of, 
63 — Propagation  of,  65. 

Excretion,  organs  of,  25— Of  plants,  theory  of,  55. 

Experiments  in  physiology,  object  of,  20 — Of 
physiologists  not  satisfactory,  22. 

F. 

Fallow,  changes  from,  52— Crops,  54— Time,  54. 
Fattening  of  animals,  49. 
Faeces,  analysis  of,  60. 
Ferment,  95,  103. 


INDEX. 


133 


Fermentation,  103 — Of  Bavarian  beer,  107 — Of 

heer^  10? — Gay-Lussac's  experiments  in,  101 

— Of    sugar,  95 — Of   vegetable   juices,  95 — 

Vinous,  103 — Of  wort,  104. 
Fertility  of  fields,  how  preserved,  61. 
Fires,  plants  on  localities  of,  52. 
Fir-wood,  analysis  of  its  ashes,  38. 
Fishes  in  salt-pans,  41. 
Flanders,  manure  in,  65. 
Fleabane,  54. 

Flesh,  effect  of  salt  on,  116. 
Flour,  bran  of,  62. 

Flowers,  colours  due  to  ammonia,  33. 
Fluorine  in  ancient  bones,  53. 
Food,  effects  on  products  of  plants,  47 — Of  young 

plants,  45 — Transformation  and  assimilation 

of,  25. 

Formation  of  wood,  47. 
Formic  acid,  theory  of  its  formation,  25— From 

hydrocyanic  acid,  25. 
Fossil  resin,  origin  of,  112. 
Franconia,  caverns  in,  43. 
Fruit,  increased,  45 — Ripening  of,  29 — Changes 

attending,  45. 
Fulminating  silver,  88. 

G. 

Gaseous  substances  in  the  lungs,  effect  of,  126. 

3asterosteus  aculeatus,  in  salt-pans,  41. 

Gay-Lussac,  his  experiments,  101. 

Germany,  cultivation  in,  61. 

Germination  of  potatoes,  45 — Of  grain,  46. 

Glass  as  a  manure,  63. 

Glue,  manure  from,  62. 

Gluten,   conversion    of,  into    yeast,  106-110 — 

Decomposition  of,  98 — Gas  from,  103. 
orrain,  germination  of,  46 — Manure  for,  40 — Rust 

in,  75. 

Granitic  soil  affords  alkalies,  40. 
Grapes,  fermentation  of,  103- — Juice  of,  differences 

in,  106 — Potash  in,  38. 
Grasses,  seeds  of,  follow  man,  41 — Silica  in,  58 — 

Valued  in  Germany,  57. 
Grauwacke,  soil  from,  50. 
Growth  of  plants,  conditions  for  the,  49. 
Guano,  67. 
Gypsum,  decomposition  of,  34 — 84 — Its  influence, 

34__Use  of,  64. 

H. 

Hay,  carbon  in,  14 — Contains  nitrogen,  59 — 
Silica,  53. 

Haystack,  effect  of  lightning  upon  a,  53. 

Hessian  and  English  weights  and  measures,  130. 

Hibernating  animals,  45. 

Horse,  urine  of  the,  35 — Concretions  in  the,  53. 

Horse  dung,  action  of  water  upon,  60 — Analysis 
of,  60. 

Human  faces,  analysis  of,  60. 

Humate  of  lime,  quantity  received  by  plants,  13. 

Humic  acid,  12,  31 — Action  of,  44 — Properties 
of,  13 — Is  not  contained  in  soils,  31 — Quantity 
received  by  plants,  14 — Insolubility  of,  44. 

Humus,  11 — Action  of,  23 — Analysis  of,  12 — 
Erroneous  opinions  concerning,  17 — Action 
upon  oxygen,  43 — Coal  of,  44 — Conversion  of 
woody  fibre  into,  110 — How  produced,  110 — 
Its  insolubility,  43 — Properties  of,  13 — Re- 
placed by  charcoal,  27 — -Source  of  carbonic 
acid,  23 — Theory  of  its  action,  23 — Unneces- 
sary for  plants,  27. 


Hydrocyanic  acid,  23,  88. 

Hydrogen,  assimilation  of,  28,  29 — Properties  of. 
10 — Excess  of,  in  wood  accounted  for,  28 — 
Of  decayed  wood,  1 1 1 — Of  plants,  source  of, 
28— Peroxide  of,  89. 

Hyett,  Mr.,  on  nitrate  of  soda,  69. 


Ice,  bubbles  of  gas  in,  20. 

Indifferent  substances,  11. 

Ingenhouss,  his  experiments,  18. 

Inorganic  compounds,  91 — Action  of,  115- — In 

what  they  differ  from  organic,  91. 
Inorganic  constituents  of  plants,  36-43. 
Iron,  oxide  of,  attracts  ammonia,  35. 
Irrigation  of  meadows,  effect  of,  43-57. 


Lactic  acid,  production  of,  98. 

Lava,  soil  from,  51. 

Lead,  salts  of,  compounds  with  organic  matter,  118. 

Leaves,  absorb  carbonic  acid,  16 — Ashes  of,  con- 
tain alkalies,  52 — Cessation  of  their  functions, 
24 — Change  colour  from  absorption  of  oxygen, 
24 — Consequence  of  the  production  of  their 
green  principle,  58 — Decompose  carbonic  acid, 
48— Their  office,  46— Power  of  absorbing  nu- 
triment, how  increased,  24 — Quantity  of  car- 
bon received  by,  16 — Contain  azotised  matter, 
63. 

Lentils,  analysis  of,  54. 

Life,  notion  of,  121. 

Light,  absence  of,  its  effect,  18— Chemical  effects 
of,  48 — Influences  decomposition  of  carbonic 
acid,  19. 

Lime,  phosphate  of,  62,  71. 

Lucerne,  phosphate  of  lime  in,  54 — Benefits  at- 
tending its  culture,  58. 

M. 

Macaire-Princep,  his  experiments,  55. 

Magnesia,  phosphate  of,  in  seeds,  22. 

Manure,  59-70 — Animal,  yields  ammonia,  33— 
Artificial,  69-71 — Carbonic  acid  from,  34 — 
Components  of,  should  be  known,  49 — Of  the 
Chinese,  65 — Effect  of,  59 — Bone,  62. 

Maple  juice,  ammonia  from,  33 — Trees,  pugar 
of,  33. 

Meadows,  irrigation  of,  43 — 57. 

Medicine,  action  of,  remedies  in,  62. 

Mellitic  acid.  112. 

Metallic  compounds  required  by  plants,  21. 

Metamorphosis,  88. 

Miasm,  defined,  127. 

Minerals  attract  ammonia,  35. 

Morbid  poisons,  121. 

Motion,  its  influence  on  chemical  forces,  89. 

Mould,  vegetable,  112 — Conversion  of  woody 
fibre  into,  112. 

Mouldering  of  bodies,  113. 

Must,  fermentation  of,  104. 

N. 

Naples,  soils  of,  52. 
Night-soil,  65. 
Nile,  soil  of  its  vicinity,  57. 
Nitrate  of  soda,  as  a  manure,  69. 
Nitric  acid  from  ammonia,  103 — animals,  30— 

How  formed,  102. 

Nitrification,  102 — Condition  for,  103. 
Nitrogen    from  animals,  30 — Account  of,  10- 

M 


134 


INDEX. 


Application  of  substances  containing  it,  34 — 
Assimilation  of,  30-36 — Chloride  of,  88 — 
Compounds  of,  11 — peculiarity  in  97 — In  ex- 
crements, 63 — From  the  atmosphere,  30 — In 
plants,  11 — Production  of,  the  object  of  agri- 
culture, 34— Transformation  of  bodies  con- 
taining, 93 — In  rice,  33 — In  solid  excrements, 
63 — In  urine,  64. 

Nutrition,  conditions  essential  to,  21 — Inorganic 
substances  required  in,  21 — Superfluous,  how 
employed,  24 — Of  young  plants,  58. 

0. 

Oaks,  ashes  of,  52 — Excretions  of,  18 — Dwarf,  23. 

Oak-wood  affords  humic  acid,  13 — Composition 
of,  110— Mouldered,  analysis  of,  111. 

Ddour  of  substances,  106 — Of  gaseous  contagious 
matter,  127. 

(Enanthic  ether,  105. 

Organs  of  excretion,  25. 

Organic  acids,  11 — Decomposition  of,  49 — Che- 
mistry, 9 — Compounds,  29 — Compared  with 
inorganic  salts  in  plants>  91. 

Organised  bodies  do  not  generate  substances,  24. 

Oxamide,  decomposition  of,  121. 

Oxides,  metallic,  in  fir-wood,  38. 

Oxygen,  action  on  alcohol,  99 — Absorption  of,  at 
night,  18 — by  leaves,  18 — respiration,  25 — 
plants,  18 — wood,  110-— Action  upon  woody 
fibre,  111 — Its  action  in  decomposition,  101 — 
Emitted  by  leaves,  15 — Given  to  air  by  land, 
28 — Extracted  from  air  by  mould,  112 — In  air, 
11 — Consumption  of,  15 — In  water,  28 — Pro- 
motes decay,  44 — Separated  during  the  forma- 
tion of  acids,  29 — Is  furnished  by  the  decom- 
position of  water,  28. 

P. 

Perennial  plants,  how  nourished,  46. 

Peroxide  of  hydrogen,  63. 

Petersen  and  Schodler,  their  analysis  of  woods,  19. 

Phosphates  necessary  to  plants,  53. 

Phosphate  of  iron,  the  probable  cause  of  rust,  75. 

Phosphoric  acid  in  ashes  of  plants,  53 — Source 
of,  53. 

Physiologists,  their  experiments  not  satisfactory, 
22 — Neglect  of  chemistry  by,  20. 

Pipe-clay,  ammonia  in,  35. 

Plants  absorb  oxygen,  18 — Ashes  of,  salts  in,  37 
— Conditions  necessary  for  their  life,  22 — De- 
cay of,  a  source  of  oxygen,  29 — Decompose 
carbonic  acid,  16 — Developement  of,  requisites 
for,  11,  40,  46,  48— Effect  of,  on  rocks,  51  — 
Elements  of,  10 — Emit  acetic  acid,  51 — Exha- 
lation of  carbonic  acid  from,  19 — Of  a  former 
world,  27 — Formation  of  their  components, 
29 — Functions  of,  16— Improve  the  air,  17 — 
Influence  of  gases  on,  18 — of  shade,  18 — In- 
organic constituents  of,  36 — Life  of,  connected 
with  that  of  animals,  9 — Milky-juiced,  in  bar- 
ren soils,  27 — Organic  acids  in,  11,  36 — salts 
in,  37 — Perennial,  nourished,  46 — Products  of, 
vary,  47 — Size  of,  proportioned  to  organs  of 
nourishment,  24 — Succession  of,  its  advantage, 
55 — Vital  processes  of,  29 — Wild,  obtain 
nitrogen  from  the  air,  34— Yield  oxygen,  17. 

Platinum  does  not  decompose  nitric  acid,  88. 

Ploughing,  its  use,  44. 

Poisons  generated  by  disease,  115 — Inorganic, 
117 — Peculiar  class  of,  119-  Rendered  inert 
by  heat,  121. 


Poisoning,  superficial,  118—  By  sausages,  120. 

Pompeii,  air  from,  15 — Bones  from,  53. 

Potash,  action  of,  upon  mould,  112 — In  grapes, 
38 — Ley  of,  its  effects  on  excrements,  34 — 
Presence  of,  in  plants,  accounted  for,  50 — Re- 
placed by  soda,  38 — Required  by  plants,  22 — 
Quantity  in  soils,  50 — Silicate  of,  in  soils,  22 
— Sources  of,  50. 

Potatoes,  oil  of,  104— Effect  of,  as  food,  47— Ger- 
mination of,  45 — Produce  of,  increased,  45. 

Products  of  transformations,  25. 

Pus,  globules  in,  124. 

Purgative  effect  of  salts  explained,  117. 

Pusey,  Mr.,  on  nitrate  of  soda,  69. 

Putrefaction,  23,  90 — Of  animals,  59 — Commu- 
nicated, 121. 

Putrefaction,  source  of  ammonia,  30 — of  carbonic 
acid,  34. 

Putrefying  sausages,  death  from,  120 — their  mode 
of  action,  120 — Substances,  their  effect  on 
wounds,  121— alkaline,  123— acid,  123. 

R. 

Rain-water,  alkali  extracted  by,  51. 

Reduction  of  oxides,  89. 

Reeds  and  canes  require  silica,  53. 

Removal  of  branches,  effects  of,  45 

Reservoirs  of  dung,  64. 

Rhine,  soils  in  its  vicinity,  57 — Wines,  105. 

Ripening  of  fruit,  45. 

Root  secretions,  55. 

Roots  absorb,  36 — Emit  extractive  matter,  55— 

Their  office,  43. 
Rotation  of  crops,  54-59. 

S. 

Saliculite  of  potash,  99. 

Saline  plants,  40. 

Salsola  kali,  38. 

Salt,  volatilisation  of,  43. 

Salts,  absorption  of,  39 — Effect  of,  on  the  or* 
ganism,  116 — Effect  of,  on  flesh,  116 — on  th« 
stomach,  116 — Organic,  in  plants,  11 — in  the 
blood,  116 — Passage  of,  through  the  lungs,  116. 

Salt-works,  loss  in,  42. 

Saltwort,  41. 

Sand,  plants  in,  27. 

Sandy  soil,  decay  of  wood  in,  111. 

Saturation,  capacity  of,  36. 

Sausages,  poisonous,  120. 

Saussure,  his  experiments  on  air,  15 — On  the 
growth  of  plants,  53. 

Schubler,  his  observations  on  rain,  31. 

Sea-water,  analysis  of,  42 — Contains  carbon,  l(i 
— Contains  ammonia,  42. 

Silica  in  grasses,  53 — In  reeds  and  canes,  53. 

Silicate  of  potash  in  plants,  22 — As  a  manure, 
63,  72. 

Silver,  carbonate  of,  action  on  organic  acids,  89— 
Salts,  poisonous  effects  of,  118. 

Sinapis  alba,  128. 

Size  of  plants  proportional  to  organs  of  nourish- 
ment, 24. 

Smell,  what,  106. 

Snow-water,  ammonia  in,  32. 

Soda  may  replace  potash,  38. 

Soils,  advantage  of  loosening,  53,  70 — Analysis 
of,  70 — Best  for  meadow-land,  40 — Carbon 
restored  to,  26 — Chemical  nature  of  its  influ- 
ence, 57 — Constituents  of,  70-84-  -Exhaustion 
of,  51 — Ferruginous,  improved,  44 — Fertile, 


INDEX. 


135 


contain  phosphoric  acid,  potash,  &c.,  82,  83 — 
Fertile,  of  Vesuvius,  51 — From  lava,  51 — Im- 
bibe ammonia,  54 — Improved  by  crops,  54 — 
Impoverished  by  crops,  54 — Various  kinds  of, 
70,  53. 

Stagnant  water,  effect  of,  44. 

Stalactites  in  caverns,  43. 

Starch,  accumulation  of,  in  plants,  45 — Compo- 
sition of,  29 — Developement  of  plants  influ- 
enced by,  45 — Effect  of,  on  malt,  26 — Product 
of,  the  life  of  plants,  18— In  willows,  45. 

Staunton,  Sir  G.,  on  Chinese  manure,  65. 

Straw,  analysis  of,  1 4. 

Struve,  experiments  of,  51. 

Substitution  of  bases,  37. 

Sussinic  acid,  112. 

Sugar,  action  of  alkalies  upon,  92 — acids  upon, 
92 — Composition  of,  95 — Carbon  in  sugar,  14 
— Contained  in  the  maple-tree,  32 — In  clero- 
dendron  fragrans,  &c.,  47 — Developement  of 
plants,  influence  on,  45 — Fermentation  of,  95 
— In  beet-roots,  32 — Metamorphosis  of,  95 — 
Organic  compounds,  all  form  sugar,  91 — Pro- 
duct of  the  life  of  plants,  18 — Transformation 
of,  93— When  produced,  24. 

Sulphur,  crystallised,  diamorphous,  90. 

Sulphuric  acid,  action  of,  on  soils,  70,  84. 

Sulphurous  acid  arrests  decay,  111. 

Swine,  urine  of,  68. 

Synaptas,  128. 

T. 

Tabasheer,  58. 

Tables  of  English  and  Hessian  weights,  130. 

Tannic  acid,  29. 

Tartaric  acid,  29 — Converted  into  sugar,  29 — In 
wine,  105. 

Teak  tree,  salts  found  in,  53. 

Teltowa  parsnep,  24,  47. 

Thenard,  his  experiments  on  yeast,  95. 

Tin,  action  on  nitric  acid,  58. 

Tobacco,  juice  contains  ammonia.  53 — Leaves  of, 
106— Nitric  acid  in,  64— In  Virginia,  51— Va- 
lue of,  proportional  to  the  quantity  of  potash  in 
the  soil,  72. 

Transformation,  by  heat,  92 — Chemical,  25,  87 
— Chemical  transformations  differ  from  decom- 
positions, 25 — Of  acetic  acid,  92 — Of  arrago- 
nite,  90 — Of  carbonic  acid,  48 — Of  meoonic 
acid,  92 — Not  affected  by  the  vital  principle, 
26 — Explained,  26 — Of  bodies  containing  ni- 
trogen, 92 — Of  bodies  destitute  of  nitrogen, 
93 — Results  of,  26 — Of  wood,  93 — Of  cyanic 
acid,  94— Of  cyanogen,  94 — Of  gluten,  104. 

Transplantation,  effect  of,  45. 

Trees,  diseases  of,  47 — Require  alkalies,  52. 

U. 

Ulmin,  12. 

Urea,  converted  into  carbonate  of  ammonia,  33 — 
In  wine,  64. 

Uric  acid,  yields  ammonia,  64 — Transformations 
of,  64. 

Urinary  calculi,  treatment  of,  26 — Organs,  elimi- 
nate nitrogen,  26. 


Urine,  contains  nitrogen,  33 — Its  use  as  manure 
68,  71— Of  men,  &c.,  64— Of  horses,  68— 
Human,  analysis  of,  64 — Of  cows,  68 — Its 
use  in  China  and  Flanders,  33,  65 — Of  swine, 
68. 

V. 

Vaccination,  its  effect,  126. 

Vegetable  albumen,  33— Mould,  112— Juices,  fer- 
mentation of,  95. 

Vesuvius,  fertile  soil  of,  51. 

Vines,  new  mode  of  manuring,  86 — Juice  of, 
yields  ammonia,  33. 

Vinous  fermentation,  103. 

Virginia,  early  products  of  its  soils,  51. 

Virus,  of  small  pox,  126— Vaccine,  126. 

Vitality,  what,  21. 

Vital  principle,  26— Value  of  the  term,  26— How 
balanced  in  the  blood,  122. 

Vital  processes  of  plants,  56. 

W. 

Water,  carbonic  acid  of,  absorbed,  16 — Composi- 
tion  of,  28— Dissolves  mould,  112— Plants, 
their  action  upon,  20 — Rain,  contains  ammo- 
nia, 31 — required  by  plants,  11 — required  by 
gypsum,  35— Salt,  analysis  of,  42. 

Wavellite,  53. 

Wheat,  analysis  of,  53 — Ashes  of,  used  as  a  ma- 
nure,  72— Exhausts,  52— Gluten  of,  33— Why 
it  does  not  thrive  on  certain  soils,  52 — In  Vir- 
ginia, 51. 

Willows,  growth  of,  45. 

Wine,  effect  of  gluten  upon,  106 — Fermentation 
of,  106— Properties  of,  106— Substances  in, 
104 — Taste  and  smell,  105 — Varieties  of,  105 

Woad,  decomposition  of,  97. 

Wood,  charcoal  may  replace  humus,  27 — a  ma- 
nure, 87 — Decayed  combustion  of,  112 — Ab- 
sorbs ammonia,  35 — Analysis  of,  19 — Conver- 
sion of,  into  humus,  110 — Decay  of,  110 — 
Requires  air,  110 — Decomposition  of,  87,  97— 
Effect  of  moisture  and  air  on,  110 — Elements 
of,  110 — Formation  of,  47 — Source  of  its  car- 
bon, 14— Transformation  of,  93. 

Wood  coal,  how  produced,  1 13 — Analysis  of,  1 14, 
115. 

Woody  fibre,  changes  in,  110 — Composition  of, 
110 — Decomposition  of,  110 — Difference  be- 
tween it  and  wood,  110 — Formation  of,  18— 
Moist,  evolves  carbonic  acid,  110 — Mould  from, 
113. 

Wormwood,  effect  of  its  culture,  41. 

Wort,  fermentation  of,  107. 

Wounds,  effect  of  putrefying  substances  on, 
120. 

Y. 

Yeast,  96 — Destroyed,  104 — Experiments  on,  98 
—Formed,  104— Its  mode  of  action,  97— Ita 
production,  119— Two  kinds  of,  107. 


Z. 

Zinc,  decomposition  of  water  with,  29 


ANIMAL  CHEMISTRY, 


OB 


ORGANIC  CHEMISTRY 


IN  ITS  APPLICATIONS  TO 


PHYSIOLOGY  AND  PATHOLOGY. 


BY  JUSTUS  LIEBIG,  M.  D.,  PH.  D.  F.  R.  S.,  M.  R.  I.  A.f 

PROFESSOR  OF  CHEMISTRY  IN  THE  UNIVERSITY  OF  GIESSEN. 


EDITED  FROM  THE  AUTHOR'S  MANUSCRIPT, 

BY  WILLIAM  GREGORY,  M.  D.,  F.  R.  S.  K,  M.  R.  I.  A. 

?R«FESSOB  OF  MEDICINE  AND  CHEMISTRY  IN  THE  UNIVERSITY  AND  ZINQ*S  COLLEGE,  ABERDKMC. 


T.  B.  PETERSON,  NO.  102  CHESTNUT  STREET, 


TO 

THE  BRITISH  ASSOCIATION 

...     -  -~-  -?—•—*. 

FOR 

THE   ADVANCEMENT    OF    SCIENCE. 


AT  the  meeting  of  the  British  Association  in  Glasgow,  in  1840, 1  had  the  honour 
to  present  the  first  part  of  a  report  on  the  then  present  state  of  Organic  Chemistry, 
in  which  I  endeavoured  to  -develope  the  doctrines  of  this  science  in  their  bearing 
on  Agriculture  and  Physiology. 

It  affords  me  now  much  gratification  to  be  able  to  communicate  to  the  meeting 
of  the  Association  for  the  present  year  the  second  part  of  my  labours ;  in  which  I 
have  attempted  to  trace  the  application  of  Organic  Chemistry  to  Animal  Physiology 
and  Pathology. 

In  the  present  work  an  extensive  series  of  phenomena  have  been  treated  in 
their  chemical  relations ;  and  although  it  would  be  presumptuous  to  consider  the 
|uestions  here  raised  as  being  definitely  resolved,  yet  those  who  are  familiar  withv 
chemistry  will  perceive  that  the  only  method  which  can  lead  to  their  final  resolu- 
tion, namely,  the  quantitative  method,  has  been  employed.  ^ 

The  formulae  and  equations  in  the  second  part,  therefore,  although  they  are  not 
to  be  viewed  as  ascertained  truths,  and  as  furnishing  a  complete,  or  the  only  ex- 
planation of  the  vital  processes  there  treated  of,  are  yet  true  in  this  sense :  that 
being  deduced  from  facts  by  logical  induction,  they  must  stand  as  long  as  no  new. 
facts  shall  be  opposed  to  them. 

When  the  chemist  shows,  for  example,  that  the  elements  of  the  bile,  added  to 
those  of  the  urate  of  ammonia,  correspond  exactly  to  those  of  blood,  he  presents 
to  us  a  fact  which  is  independent  of  all  hypothesis.  It  remains  for  the  physiolo- 
gist to  determine,  by  experiment,  whether  the  conclusions  drawn  by  the  chemist 
from  such  a  fact  be  accurate  or  erroneous.  And  whether  this  question  be  answered 
in  the  affirmative  or  in  the  negative,  the  fact  remains,  and  will  some  day  find  its 
true  explanation. 

I  have  now  to  perform  the  agreeable  duty  of  expressing  my  sense  of  the  services 
rendered  to  me  in  the  preparation  of  the  English  edition  by  my  friend,  Dr.  Gregory. 
The  distinguished  station  he  occupies  as  a  chemist ;  the  regular  education  which 
he  has  received  in  the  various  branches  of  medicine ;  and  his  intimate  acquaintance 
with  the  German  language — all  these,  taken  together,  are  the  best  securities  that 
the  translation  is  such  as  to  convey  the  exact  sense  of  the  original ;  securities, 
such  as  are  not  often  united  in  the  same  individual. 

It  is  my  intention  to  follow  this  second  part  with  a  third,  the  completion  of 
which,  however,  cannot  be  looked  for  before  the  lapse  of  two  years.  This  third 
part  will  contain  an  investigation  of  the  food  of  man  and  animals,  the  analysis  of 
all  articles  of  diet,  and  the  study  of  the  changes  which  the  raw  food  undergoes  in 
its  preparation ;  as,  for  example,  in  fermentation  (bread,)  baking,  roasting,  boiling, 
&,c.  Already,  it  is  true,  many  analyses  have  been  made  for  the  proposed  work ; 
but  the  number  of  objects  of  investigation  is  exceedingly  large,  and  in  order  to 
determine  with  accuracy  the  absolute  value  of  seed,  or  of  flour,  or  of  a  species  of 
fodder,  8tc.,  as  food,  the  ultimate  analysis  alone  is  not  sufficient;  there  are  required 
comparative  investigations,  which  present  very  great  difficulties. 

DR.  JUSTUS  LIEBIG. 
Giessen*  3d  June.  1852. 

(3) 


NOTE. 

1  WOULD  beg  leave  to  refer  the  chemical  as  well  as  the  physiological  reader 
ticularly  to  the  analyses  (in  Note  (27)  Appendix)  of  the  animal  tissues,  which 
ought  to  have  been  referred  to  on  pages  21  and  42,  and  which  at  present  are  only 
referred  to  in  Note  (7.)  Since  the  work  was  printed,  moreover,  there  has  been 
added,  at  the  end  of  the  Appendix,  an  interesting  paper  by  Keller  (see  page  101,) 
confirming  the  very  important  observation  of  A.  Ure,  junior,  as  to  the  conversion  of 
benzoic  acid  into  hippuric  acid  in  the  human  body ;  a  fact  which,  I  perceive,  by  the 
Philosophical  Magazine  for  June,  has  also  been  confirmed  by  Mr.  Garrod,  probably 
at  an  earlier  period  than  by  M.  Keller.  The  reader  will  perceive  that  this  fact 
strengthens  materially  the  argument  of  the  Author  on  the  action  of  remedies. 

W.  G. 


PREFACE. 


BY  the  application  to  chemistry  of  the  methods  which  had  for  centuries  been 
followed  by  philosophers  in  ascertaining  the  causes  of  natural  phenomena  in 
physics — by  the  observation  of  weight  and  measure — LAVOISIER  laid  the  founda- 
tion of  a  new  science,  which,  having  been  cultivated  by  a  host  of  distinguished 
men,  has,  in  a  singularly  short  period,  reached  a  high  degree  of  perfection. 

It  was  the  investigation  and  determination  of  all  the  conditions  which  are  essen- 
tial to  an  observation  or  an  experiment,  and  the  discovery  of  the  true  principles  of 
scientific  research,  that  protected  chemists  from  error,  and  conducted  them,  by  a 
way  equally  simple  and  secure,  to  discoveries  which  have  shed  a  brilliant  light  on 
those  natural  phenomena  which  were  previously  the  most  obscure  and  incompre- 
hensible. 

The  most  useful  applications  to  the  arts,  to  industry,  and  to  all  branches  of 
knowledge  related  to  chemistry,  sprung  from  the  laws  thus  established ;  and  this 
influence  was  not  delayed  till  chemistry  had  attained  its  highest  perfection,  but 
came  into  action  with  each  new  observation. 

All  existing  experience  and  observation  in  other  departments  of  science  reacted, 
in  like  manner,  on  the  improvement  and  development  of  chemistry;  so  that 
chemistry  received  from  metallurgy  and  from  other  industrial  arts  as  much  benefit 
as  she  had  conferred  on  them.  While  they  simultaneously  increased  in  wealth, 
they  mutually  contributed  to  the  development  of  each  other. 

After  mineral  chemistry  had  gradually  attained  its  present  state  of  development, 
the  labours  of  chemists  took  a  new  direction.  From  the  study  of  the  constituent 
parts  of  vegetables  and  animals,  new  and  altered  views  have  arisen;  and  the 
present  work  is  an  attempt  to  apply  these  views  to  physiology  and  pathology. 

In  earlier  times  the  attempt  has  been  made,  and  often  with  great  success,  to 
apply  to  the  objects  of  the  medical  art  the  views  derived  from  an  acquaintance  with 
chemical  observations.  Indeed,  the  great  physicians,  who  lived  towards  the  end 
of  the  seventeenth  century,  were  the  founders  of  chemistry,  and  in  those  days  the 
only  philosophers  acquainted  with  it.  The  phlogistic  system  was  the  dawn  of  a 
new  day ;  it  was  the  victory  of  philosophy  over  the  rudest  empiricism. 

With  all  its  discoveries,  modern  chemistry  has  performed  but  slender  services  to 
physiology  and  pathology ;  and  we  cannot  be  deceived  as  to  the  cause  of  this 
failure,  if  we  reflect  that  it  was  found  impossible  to  trace  any  sort  of  relation  be- 
tween the  observations  made  in  inorganic  chemistry,  the  knowledge  of  the  charac- 
ters of  the  elementary  bodies  and  of  such  of  their  compounds  as  could  be  formed 
in  the  laboratory,  on  the  one  hand,  and  the  living  body,  with  the  characters  of  its 
constituents,  on  the  other. 

Physiology  took  no  share  in  the  advancement  of  chemistry,  because  for  a  long 
period  she  received  from  the  latter  science  no  assistance  in  her  own  development. 
This  state  of  matters  has  been  entirely  changed  within  five  and  twenty  years.  But 
during  this  period  physiology  has  also  acquired  new  ways  and  methods  of  investi- 
gation within  her  own  province ;  and  it  is  only  the  exhaustion  of  these  sources  oi 

A2  5 


Vi  PREFACE 

discovery  which  has  enabled  us  to  look  forward  to  a  change  in  the  direction  of  the 
labours  of  physiologists.  The  time  for  such  a  change  is  now  at  hand ;  and  a  per- 
severance in  the  methods  lately  followed  in  physiology  would  now,  from  the  want, 
which  must  soon  be  felt,  of  fresh  points  of  departure  for  researches,  render  phy- 
siology more  extensive,  but  neither  more  profound  nor  more  solid. 

No  one  will  venture  to  maintain  that  the  knowledge  of  the  forms  and  of  the 
phenomena  of  motion  in  organized  beings  is  either  unnecessary  or  unprofitable. 
On  the  contrary,  this  knowledge  must  be  considered  as  altogether  indispensable 
to  that  of  the  vital  processes.  But  it  embraces  only  one  class  of  the  conditions 
necessary  for  the  acquisition  of  that  knowledge,  and  is  not  of  itself  sufficient  to 
enable  us  to  attain  it. 

The  study  of  the  uses  and  functions  of  the  different  organs,  and  of  their  mutual 
connection  in  the  animal  body,  was  formerly  the  chief  object  of  physiological  re- 
searches ;  but  lately  this  study  has  fallen  into  the  back-ground.  The  greater  part 
of  all  the  modern  discoveries  has  served  to  enrich  comparative  anatomy  far  more 
than  physiology. 

These  researches  have  yielded  the  most  valuable  results  in  relation  to  the  recog- 
nition of  the  dissimilar  forms  and  conditions  to  be  found  in  the  healthy  and  in  the 
diseased  organism ;  but  they  have  yielded  no  conclusions  calculated  to  give  us  a 
more  profound  insight  into  the  essence  of  the  vital  processes. 

The  most  exact  anatomical  knowledge  of  the  structure  of  the  tissues  cannot 
teach  us  their  uses ;  and  from  the  microscopical  examination  of  the  most  minute 
reticulations  of  the  vessels  we  can  learn  no  more  as  to  their  functions  than  we 
have  learned  concerning  vision  from  counting  the  surfaces  on  the  eye  of  the  fly. 
The  most  beautiful  and  elevated  problem  for  the  human  intellect,  the  discovery  of 
the  laws  of  vitality,  cannot  be  resolved,  nay,  cannot  even  be  imagined,  without  an 
accurate  knowledge  of  chemical  forces  ;  of  those  forces  which  do  not  act  at  sensi- 
ble distances ;  which  are  manifested  in  the  same  way  as  those  ultimate  causes  by 
which  the  vital  phenomena  are  determined ;  and  which  are  invariably  found  active, 
whenever  dissimilar  substances  come  into  contact. 

Physiology,  even  in  the  present  day,  still  endeavours,  but  always  after  the 
fashion  of  the  phlogistic  chemis-ts  (that  is,  by  the  qualitative  method,)  to  apply 
chemical  experience  to  the  removal  of  diseased  conditions;  but  with  all  these 
countless  experiments  we  are  not  one  step  nearer  to  the  causes  and  the  essence  of 
disease. 

With  proposing  well-defined  questions,  experimenters  have  placed  blood,  urine, 
and  all  the  constituents  of  the  healthy  or  diseased  frame,  in  contact  with  acids, 
alkalies,  and  all  sorts  of  chemical  re-agents ;  and  have  drawn,  from  observation  of 
the  changes  thus  produced,  conclusions  as  to  their  behaviour  in  the  body. 

By  pursuing  this  method,  useful  remedies  or  modes  of  treatment  might  by  acci- 
dent be  discovered ;  but  a  rational  physiology  cannot  be  founded  on  mere  re-actions, 
and  the  living  body  cannot  be  viewed  as  a  chemical  laboratory. 

In  certain  diseased  conditions,  in  which  the  blood  acquires  a  viscid  consistence, 
this  state  cannot  be  permanently  removed  by  a  chemical  action  on  the  fluid  circu- 
lating in  the  blood-vessels.  The  deposit  of  a  sediment  from  the  urine  may 
perhaps,  be  prevented  by  alkalies,  while  their  action  has  not  the  remotest  tendency 
to  remove  the  cause  of  disease.  Again,  when  we  observe,  in  typhus,  insoluble  salts 
of  ammonia  in  the  faeces,  and  a  change  in  the  globules  of  the  blood  similar  to  that 
which  may  be  artificially  produced  by  ammonia,  we  are  not,  on  that  account, 


PREFACE  Til 

entitled  to  consider  the  presence  of  ammonia  in  the  body  as  the  cause,  but  only  as 
the  effect  of  a  cause. 

Thus  medicine,  after  the  fashion  of  the  Aristotelian  philosophy,  has  formed 
certain  conceptions  in  regard  to  nutrition  and  sanguification ;  articles  of  diet  have 
been  divided  into  nutritious  and  non-nutritious ;  but  these  theories,  being  founded 
on  observations  destitute  of  the  conditions  most  essential  to  the  drawing  of  just 
conclusions,  could  not  be  received  as  expressions  of  the  truth. 

How  clear  are  now  to  us  the  relations  of  the  different  articles  of  food  to  the 
objects  which  they  serve  in  the  body,  since  organic  chemistry  has  applied  to  the 
investigation  her  quantitative  method  of  research ! 

When  a  lean  goose,  weighing  4  Ibs/,  gains,  in  thirty- six  days,  during  which  it 
has  been  fed  with  24  Ibs.  of  maize,  5  Ibs.  in  weight  and  yields  3  J  Ibs.  of  pure  fat, 
this  fat  cannot  have  been  contained  in  the  food,  ready  formed,  because  maize  does 
not  contain  the  thousandth  part  of  its  weight  of  fat,  or  of  any  substance  resembling 
fat.  And  when  a  certain  number  of  bees,  the  weight  of  which  is  exactly  known, 
being  fed  with  pure  honey,  devoid  of  wax,  yield  one  part  of  wax  for  every  twenty 
parts  of  honey  consumed,  without  any  change  being  perceptible  in  their  health  or 
in  their  weight,  it  is  impossible  any  longer  to  entertain  doubt  as  to  the  formation 
of  fat  from  sugar  in  the  animal  body. 

We  must  adopt  the  method  which  has  thus  led  to  the  discovery  of  the  origin  of 
fat,  in  the  investigation  of  the  origin  and  alteration  of  the  secretions,  as  well  as  in 
the  study  of  all  the  other  phenomena  of  the  animal  body.  From  the  moment  that 
we  begin  to  look  earnestly  and  conscientiously  for  the  true  answers  to  our  ques- 
tions, that  we  take  the  trouble,  by  means  of  weight  and  measure,  to  fix  our  obser- 
vations, and  express  them  in  the  form  of  equations,  these  answers  are  obtained 
without  difficulty. 

However  numerous  our  observations  may  be,  yet,  if  they  only  bear  on  one  side 
of  a  question,  they  will  never  enable  us  to  penetrate  the  essence  of  a  natural  phe- 
nomenon in  its  full  significance.  If  we  are  to  derive  any  advantage  from  them, 
they  must  be  directed  to  a  well  defined  object ;  and  there  must  be  an  organized 
connection  between  them. 

Mechanical  philosophers  and  chemists  justly  ascribe  to  their  methods  of  research 
the  greater  part  of  the  success  which  has  attended  their  labours.  The  result  of 
every  such  investigation,  if  it  bear  in  any  degree  the  stamp  of  perfection,  may 
always  be  given  in  few  words;  but  these  few  words  are  eternal  truths,  to  the 
discovery  of  which  numberless  experiments  and  questions  were  essential.  The 
researches  themselves,  the  laborious  experiments  and  complicated  apparatus,  are 
forgotten  as  soon  as  the  truth  is  ascertained.  They  were  the  ladders,  the  shafts, 
the  tools,  which  were  indispensable  to  enable  us  to  attain  to  the  rich  vein  of  ore ; 
they  were  the  pillars  and  air  passages  which  protected  the  mine  from  water  and 
from  foul  air. 

Every  chemical  or  physical  investigation,  however  insignificant,  which  lays 
claim  to  attention,  must  in  the  present  day  possess  this  character.  From  a  certain 
number  of  observations  it  must  enable  us  to  draw  some  conclusion,  whether  it  be 
extended  or  limited. 

The  imperfection  of  the  method  or  system  of  research  adopted  by  physiologists 
can  alone  explain  the  fact,  that  for  the  last  fifty  years  they  have  established  so  few 
new  and  solid  truths  in  regard  to  a  more  profound  knowledge  of  the  functions  of 
the  most  important  organs,  of  the  spleen,  cf  the  liver,  and  of  the  numerous  glands 


Vlll  PREFACE. 

of  the  body ;  and  the  limited  acquaintance  of  physiologists  with  the  methods  of 
research  employed  in  chemistry  will  continue  to  be  the  chief  impediment  to  the 
progress  of  physiology,  as  well  as  a  reproach  which  that  science  cannot  escape, 

Before  the  time  of  Lavoisier,  Scheele,  and  Priestley,  chemistry  was  not  more 
closely  related  to  physics  than  she  is  now  to  physiology.  At  the  present  day 
chemistry  is  so  fused,  as  it  were,  into  physics,  that  it  would  be  a  difficult  matter 
to  draw  the  line  between  them  distinctly.  The  connection  between  chemistry  and 
physiology  is  the  same,  and  in  another  half  century  it  will  be  found  impossible  to 
separate  them. 

Our  questions  and  our  experiments  intersect  in  numberless  curved  lines  the 
straight  line  that  leads  to  truth.  It  is  the  p6ints  of  intersection  that  indicate  to  us 
the  true  direction ;  but,  owing  to  the  imperfection  of  the  human  intellect,  these 
curve  lines  must  be  pursued.  Observers  in  chemistry  and  physics  have  the  eye 
ever  fixed  on  the  object  which  they  seek  to  attain.  One  may  succeed,  for  a  space, 
in  following  the  direct  line;  but  all  are  prepared  for  circuitous  paths.  Never 
doubting  of  the  ultimate  success  of  their  efforts,  provided  they  exhibit  constancy 
and  perseverance,  their  eagerness  and  courage  are  only  exalied  by  difficulties. 

Detached  observations,  without  connection,  are  points  scattered  over  the  plain, 
which  do*  not  allow  us  to  choose  a  decided  path.  For  centuries  chemistry  pre- 
sented nothing  but  these  points,  and  sufficient  means  were  available  to  fill  up  the 
intervals  between  them.  But  permanent  discoveries  and  real  progress  were  only 
made  when  chemists  ceased  to  make  use  of  fancy  to  connect  them. 
/  My  object  in  the  present  work  has  been  to  direct  attention  to  the  points  of  inlex- 
section  of  chemistry  with  physiology,  and  to  point  out  those  parts  in  which  the 
sciences  become,  as  it  were,  mixed  up  together.  It  contains  a  collection  of 
problems,  such  as  chemistry  at  present  requires  to  be  resolved ;  and  a  number  of 
conclusions  drawn  according  to  the  rules  of  that  science  from  such  observations 
as  have  been  made. 

These  questions  and  problems  will  be  resolved :  and  we  cannot  doubt  that  we 
shall  have  in  that  case  a  new  physiology  and  a  rational  pathology.  Our  sounding 
line,  indeed,  is  not  long  enough  to  measure  the  depths  of  the  sea,  but  is  not  on 
that  account  less  valuable  to  us :  if  it  assist  us,  in  the  mean  time,  to  avoid  rocks 
and  shoals,  its  use  is  sufficiently  obvious.  In  the  hands  of  the  physiologist,  organic 
chemistry  must  become  an  intellectual  instrument,  by  means  of  which  he  will  be 
enabled  to  trace  the  causes  of  phenomena  invisible  to  the  bodily  sight ;  and  if 
among  the  results  which  I  have  developed  or  indicated  in  this  work,  one  alone 
shall  admit  of  a  useful  application,  I  shall  consider  the  object  for  which  it  was 
written  as  fully  attained.  The  path  which  has  led  to  it  will  open  up  other  paths  j 
and  this  I  consider  as  the  most  important  cbject  to  be  gained. 

JUSTUS  LIEB  G. 

Giessen,  April,  1852. 


CONTENTS. 


PART  I. 


Page 
11 


Vital  force,  vis  vitse,  or  vitality    . 
Distinction  between  animal  and  vegeta- 
ble life      11 

Assimilation  the  result  of  chemical  forces     1 2 
Vitality  independent  of  consciousness  .     12 
Laws  of  the  vital  force          .        .        .13 
Conditions  of  animal  life      .        .        .13 
Nutrition  depends  on  chemical  changes     13 
Amount  of  oxygen  inspired  by  an  adult 
man.         ......     14 

It  combines  with  carbon  and  hydrogen 
in  the  body        .         .         .         .         .14 

The  consumption  of  oxygen  varies       .     14 
Effect  of  heat  on  these  variations.        .    15 
The  mutual  action  of  oxygen  and  car- 
bon in  the  body  is  the  true  source  of 
animal  heat       .  •      .    "  *.. .,      .        .     15 
The  amount  of  oxygen  regulates  that  of 

food 16 

Effects  of  climate  on  the  appetite         .     16 
The  process  of  starvation     .        .        .17 
Cause  of  death  in  starvation  and  chro- 
nic diseases       .  .        .        .     17 
Nerves  and  muscles  not  the  source  of 

animal  body  .  .  ,  -.-  '  .  .18 
Amount  of  animal  heat  .  .  .19 
Nervous  and  vegetative  life  .  .  .20 
Nutrition  depends  on  the  constituents  . 

of  blood 21 

Identity  of  organic  composition  infibrme 
and  albumen    .        .        .        .        .21 

Nutrition   in  the  carnivora  the  most 
simple      ......    22 

In  the  herbivora,  depends  on  the  azo- 

tized  products  of  vegetables      .        .    22 
These  products  identical  with  the  con- 
stituents of  blood       .        .        .        .22 

The  blood  of  animals  is  therefore  formed 

by  vegetables 23 

Uses  of  the  non-azotized  ingredients  of 
food          .        .        .        .        .        .23 

Changes  of  the  food  in  the  organism  of 
carnivora  .        .        .        .        .        .t  24 

Carbon  accumulates  in  the  bile    *-.        .    25 
Nitrogen  in  the  urine    .        .        .        .25 

2 


Page 

The  carbon  is  consumed  or  burned  .  26 
True  function  of  the  bile  .  .  ,26 
Amount  of  bile  secreted  .  .  .27 
Assimilation  more  energetic  in  the 

young  animal   .        .        .        .        .27 
The  butter,  sugar,  &c.,  of  its  food  sup- 
port respiration         .        .        .        .28 
The  same  is  true  of  the  class  of  herbivora    28 
Waste  of  matter  very  rapid  in  carnivora    30 
Importance  of  agriculture  to  population     30 
Assimilation  less  energetic  in  the  carni- 
vora  31 

Origin  of  fat  in  domesticated  animals  .  31 
Its  formation  is  a  source  of  oxygen  .  32 
It  is  formed  when  oxygen  is  deficient, 

and  is  a  source  of  animal  heat .        .    33 
Elements  of  nutrition  and  of  respiration    35 
Gelatine  incapable  of  serving  for  nutri- 
tion, strictly  so  called        .        .         .35 
But  it  may  serve  to  nourish  the  gelati- 
nous tissues 35 

PART  II. 

THE   METAMORPHOSIS   OP   TISSUES. 

Discovery  of  proteine  .        .        .        .36 

It  is  formed  by  vegetables  alone   .        .    37 
Theory  of  chymification       .        .        .37 
Use  of  the  saliva ...        .        .        .38 

Source  of  the  nitrogen  exhaled  from 

the  lungs  and  skin  .  .  .  .39 
Composition  of  proteine  .  .  .41 
Composition  of  the  animal  tissues  .  42 
Gelatine  contains  no  proteine,  although 

formed  from  it 42 

The  secretions  contain  all  the  elements 

of  the  blood  .  .  .  .  .43 
Formula  of  blood  and  metamorphoses 

of  bile 44 

Metamorphoses  of  blood  and  flesh  .  44 
The  constituents  of  the  urine  derived 

from  the  metamorphosed  tissues  .  45 
Relation  of  blood  or  flesh  and  proteins 

to  the  secretions  and  excretions  .  45 
Formation  of  gelatine  .  .  .  .46 
Origin  of  bile  in  the  carnivora  .  47 

Origin  of  bile  in  the  herbivora  .  47 

ix 


CONTENTS. 


Pagej 

Origin  of  hippuric  acid  .  .  .48 
Formation  of  the  chief  secretions  and 

excretions 48 

Soda  essential  to  the  bile  .  .  .49 
Relation  of  urine  to  bile  .  .  .50 
Relation  of  starch  to  biJe  .  .  .51 
Uses  of  common  salt  .  .  .  .  52 
Certain  remedies  take  a  share  in  the 

vital  transformations  .  •  .54 
Chief  qualities  of  the  blood  .  .  .  54 
Modus  operandi  of  organic  remedies  .  55 
All  organic  poisons  contain  nitrogen  .  56 
Theine  identical  with  caffeine  .  .  56 
Relation  of  theine  and  caffeine  to  bile  .  56 
Theory  of  their  action  .  .  .  .57 
Theory  of  the  action  of  the  vegetable 

alkalies 57 

Composition    and    origin   of  nervous 

matter      .        .        .        •    '    V       •    57 
It  is  related  to  that  of  the  vegetable  al- 
kalies         58 

Theory  of  the  action  of  the  latter .        ,    59 


Page 

Phosphorus  seems  essential  to  nervous 

matter       ......    59 

1 

PART  III. 

1.  The  phenomena  of  motion  in  the 
animal  organism      .        .        .        .60 

2.  The  same  subject,  with  particular 
reference  to  the  waste  and  supply  or 
change  of  matter       .        .        .        .69 

3.  Theory  of  disease    .        .        .        .74 

4.  Theory  of  respiration       .        .        .77 

APPENDIX. 

Containing  the  analytical  evidence  re- 
ferred to  in  the  sections  in  which  are 
described  the  chemical  processes  of 
respiration,  nutrition,  and  the  meta- 
morphosis of  tissues  •  .  .80 

On  the  conversion  of  benzoic  acid  into 
hippuric  acid  in  the  human  body,  by 
W.  Keller  .  101 


INDEX 


.  103 


ORGANIC    CHEMISTRY 


APPLIED   TO 


PHYSIOLOGY  AND  PATHOLOGY. 


I.  IN  the  animal  ovum,  as  well  as  in  the 
eeed  of  a  plant,  we  recognise  a  certain  re- 
markable force,  the  source  of  growth,  or  in- 
crease in  the  mass,  and  of  reproduction,  or 
of  supply  of  the  matter  consumed;  a  force 
in  a  state  of  rest.  By  the  action  of  external 
influences,  by  impregnation,  by  the  pre- 
sence of  air  and  moisture,  the  condition  of 
static  equilibrium  of  this  force  is  disturbed  ; 
entering  into  a  state  of  motion  or  activity, 
it  exhibits  itself  in  the  production  of  a  series 
of  forms,  which,  although  occasionally 
bounded  by  right  lines,  are  yet  widely  dis- 
inct  from  geometrical  forms,  such  as  we  ob- 
serve in  crystallised  minerals.  This  force  is 
called  the  vital  force,  or  viz  vitce  vitality. 

The  increase  of  mass  in  a  plant  is  deter- 
mined by  the  occurrence  of  a  decomposition 
which  takes  place  in  certain  parts  of  the 
plant  under  the  influence  of  light  and  heat. 

In  the  vital  process,  as  it  goes  on  in 
vegetables,  it  is  exclusively  inorganic  matter 
which  undergoes  this  decomposition ;  and 
if,  with  the  most  distinguished  mineralo- 
gists, we  consider  atmospherical  air  and 
certain  other  gases  as  minerals,  it  may  be 
said  that  the  vital  process  in  vegetables  ac- 
complishes the  transformation  of  mineral 
substances  into  an  organism  endued  with 
life ;  that  the  mineral  becomes  part  of  an 
organ  possessing  vital  force. 

The  increase  of  mass  in  a  living  plant 
implies  that  certain  component  parts  of  its 
nourishment  become  component  parts  of 
the  plant;  and  a  comparison  of  the  chemical 
composition  of  the  plant  with  that  of  its 
nourishment,  makes  known  to  us,  with 
positive  certainty,  which  of  the  component 
parts  of  the  latter  have  been  assimilated,  and 
whicn  have  been  rejected. 

The  observations  of  vegetable  physiolo- 
gists and  the  researches  of  chemists  have 
mutually  contributed  to  establish  the  fact, 
that  the  growth  and  development  of  vege- 
tables depend  on  the  elimination  of  oxygen, 
which  is  separated  from  the  other  compo- 
nent parts  of  their  nourishment. 

In  contradiction  to  vegetable  life,  the  life 
of  animals  exhibits  itself  in  the  continual 
absorption  of  the  oxygen  of  the  air,  and  its 
combination  with  certain  component  parts 
of  ihe  anirna^  body 


While  no  part  of  an  organized  being  can 
serve  as  food  to  vegetables,  until,  by  the 
processes  of  putrefaction  and  decay,  it  has 
assumed  the  form  of  inorganic  matter,  the 
animal  organism  requires,  for  its  support 
and  development,  highly  organized  atoms. 
The  food  of  all  animals,  in  all  circum- 
stances, consists  of  parts  of  organisms. 

Animals  are  distinguished  from  vegeta- 
bles by  the  faculty  of  locomotion,  and,  in 
general,  by  the  possession  of  senses. 

The  existence  and  activity  of  these  dis- 
tinguishing faculties  depend  on  certain  in- 
struments which  are  never  found  in  vegeta- 
bles. Comparative  anatomy  shows,  that 
the  phenomena  of  motion  and  sensation  de- 
pend on  certain  kinds  of  apparatus,  which 
have  no  other  relation  to  each  other  than 
this,  that  they  meet  in  a  common  centre. 
The  substance  of  the  spinal  marrow,  the 
nerves,  and  the  brain,  is  in  its  composition, 
and  in  its  chemical  characters,  essentially 
distinct  from  that  of  which  cellular  sub- 
stance, membranes,  muscles,  and  skin  are 
composed. 

Every  thing  in  the  animal  organism,  to 
which  the  name  of  motion  can  be  applied, 
proceeds  from  the  nervous  apparatus.  The 
phenomena  of  motion  in  vegetables,  the 
circulation  of  the  sap,  for  example,  observed 
in  many  of  the  characeae,  and  the  closing  ot 
flowers' and  leaves,  depend  on  physical  and 
mechanical  causes.  A  plant  is  destitute  of 
nerves.  Heat  and  light  are  the  remote 
causes  of  motion  in  vegetables ;  but  in  ani- 
mals we  recognise  in  the  nervous  apparatus 
a  source  of  power,  capable  of  renewing 
itself  at  every  moment  of  their  existence. 

While  the  assimilation  of  food  in  vegeta- 
bles, and  the  whole  process  of  their  forma  • 
tion,  are  dependant  on  certain  external  in  • 
fluences  which  produce  motion,  the  deve 
lopment  of  the  animal  organism  is,  to  a 
certain  extent,  independent  of  these  external 
influences,  just  because  the  animal  body 
can  produce  within  itself  that  source  of  mo- 
tion which  is  indispensable  to  the  vital  pro- 
cess. 

Assimilation,  or  the  process  of  formation 
and  growth — in  other  words,  the  passage  of 
matter  from  a  stato  of  motion  to  that  of  rest 
— goes  on  in  the  same  way  in  animals  and 


12 


ANIMAL  CHEMISTR1. 


in  vegetables.  In  both,  the  same  cause  de- 
termines the  increase  of  mass.  This  con- 
stitutes the  true  vegetative  life,  which  is 
carried  on  without  consciousness. 

The  activity  of  vegetative  life  manifests 
itself,  in  vegetables,  with  the  aid  of  external 
influences ;  in  animals,  by  means  of  in- 
fluences produced  within  their  organism. 
Digestion,  circulation,  secretion,  are  no 
doubt  under  the  influence  of  the  nervous 
system ;  but  the  force  which  gives  to  the 
germ,  Ue  leaf,  and  the  radical  fibres  of  the 
vegetable  the  same  wonderful  properties,  is 
the  same  as  that  residing  in  the  secreting 
membranes  and  glands  of  animals,  and 
which  enables  every  animal  organ  to  per- 
form its  own  proper  function.  It  is  only 
the  source  of  motion  that  differs  in  the  two 
great  classes  of  organized  beings. 

While  the  organs  of. the  vital  motions  are 
never  wanting  in  the  lowest  orders  of  ani- 
mals, as  in  the  impregnated  germ  of  the 
ovum,  in  which  they  are  developed  first  of 
all,  we  find,  in  the  higher  orders  of  animals, 
peculiar  organs  of  feeling  and  sensation,  of 
consciousness  and  of  a  higher  intellectual 
existence. 

Pathology  informs  us  that  the  true  vege- 
tative life  is  in  no  way  dependant  on  the 
presence  of  this  apparatus  ;  that  the  process 
of  nutrition  proceeds  in  those  parts  of  the 
body  where  the  nerves  of  sensation  and 
voluntary  motion  are  paralysed,  exactly  in 
the  same  way  as  in  other  parts  where  these 
nerves  are  in  the  normal  condition ;  and,  on 
the  other  hand,  that  the  most  energetic  voli- 
tion is  incapable  of  exerting  any  influence 
on  the  contractions  of  the  heart,  on  the  mo- 
tion of  the  intestines,  or  on  the  processes 
of  secretion. 

The  higher  phenomena  of  mental  exist- 
ence cannot,  in  the  present  state  of  science, 
be  referred  to  their  proximate,  and  still  less 
to  their  ultimate  causes.  We  only  know  of 
them,  that  they  exist ;  we  ascribe  them  to 
an  immaterial  agency,  and  that,  in  so- far  as 
its  manifestations  are  connected  with  matter, 
an  agency  entirely  distinct  from  the  vital 
force,  with  which  it  has  nothing  in  common. 

It  cannot  be  denied  that  this  peculiar  force 
exercises  a  certain  influence  on  the  activity 
of  vegetative  life,  just  as  other  immaterial 
agents,  such  as  Light,  Heat,  Electricity,  and 
Magnetism  dp ;  but  this  influence  is  not  of 
a  determinative  kind,  and  manifests  itself 
only  as  an  acceleration,  a  retarding,  or  a  dis- 
turbance of  the  process  of  vegetative  life.  In 
a  manner  exactly  analogous,  the  vegetative 
life  re-acts  on  the  conscious  mental  existence. 

There  are  thus  two  forces  which  are  found 
in  activity  together;  but  consciousness  and 
intellect  may  be  absent  in  animals  as  they 
are  in  living  vegetables,  without  their  vitality 
being  otherwise  affected  than  by  the  want 
of  a  peculiar  source  of  increased  energy  or 
of  disturbance.  Except  in  regard  to  this, 
all  the  vital  chemical  processes  go  on  pre- 
cisely in  the  same  way  in  man  and  in  the 
lower  animals. 


The  efforts  of  philosophers,  constantly  re 
newed,  to  penetrate  the  relations  of  the  soul 
to  animal  life,  have  all  along  retarded  the 
progress  of  physiology.  In  this  attempt 
men  left  the  province  of  philosophical  re- 
search for  that  of  fancy ;  physiologists,  car- 
ried away  by  imagination,  were  far  from 
being  acquainted  with  the  laws  of  purely 
animal  life.  None  of  them  had  a  clear  con- 
ception of  the  process  of  development  and 
nutrition,  or  of  the  true  cause  of  death. 
They  professed  to  explain  the  most  obscure 
psychological  phenomena,  and  yet  they  were 
unable  to  say  what  fever  is,  and  in  what 
way  quinine  acts  in  curing  it. 

For  the  purpose  of  investigating  the  laws 
of  vital  motion  in  the  animal  body,  only  one 
condition,  namely,  the  knowledge  of  the 
apparatus  which  serves  for  its  production, 
was  ascertained ;  but  the  substance  of  the 
organs,  the  changes  which  food  undergoes 
in  the  living  body,  its  transformation  into 
portions  of  organs,  and  its  reconversion  into 
lifeless  compounds,  the  share  which  the  at- 
mosphere takes  in  the  processes  of  vitality ; 
all  these  foundations  for  future  conclusions 
were  still  wanting. 

What  has  the  soul,  what  have  conscious- 
ness and  intellect  to  do  with  the  develop- 
ment of  the  human  foetus,  or  the  foetus  in  a 
fowl's  egg?  not  more,  surely,  than  with  the 
development  of  the  seeds  of  a  plant.  Let 
us  first  endeavour%to  refer  to  their  ultimate 
causes  those  phenomena  of  life  which  are 
not  physiological ;  and  let  us  beware  of 
drawing  conclusions  before  we  have  a 
groundwork.  We  know  exactly  the  me- 
chanism of  the  eye;  but  neither  anatomy 
nor  chemistry  will  ever  explain  how  the 
rays  of  light  act  on  consciousness,  so  as  to 
produce  vision.  Natural  science  has  fixed 
limits  which  cannot  be  passed;  and  it  must 
always  be  borne  in  mind  that,  with  all  our 
discoveries,  we  shall  never  know  what  light, 
electricity,  and  magnetism  are  in  their  es- 
sence, because,  even  of  those  things  which 
are  material,  the  human  intellect  has  only 
conceptions.  We  can  ascertain,  however, 
the  laws  which  regulate  their  motion  and 
rest,  because  these  are  manifested  in  pheno- 
mena. In  like  manner  the  laws  of  vitality, 
and  of  all  that  disturbs,  promotes,  or  alters 
it,  may  certainly  be  discovered,  although  we 
shall  never  learn  what  life  is.  Thus  the 
discovery  of  the  laws  of  gravitation  and  of 
the  planetary  motions  led  to  an  entirely  new 
conception  of  the  cause  of  these  phenomena. 
This  conception  could  not  have  been  formed 
in  all  its  clearness  without  a  knowledge  of 
phenomena  out  of  which  it  was  evolved  ; 
for,  considered  by  itself,  gravity,  like  light 
to  one  born  blind,  is  a  mere  word,  devoid  of 
meaning. 

The  modern  science  of  physiology  has 
left  the  track  of  Aristotle.  To  the  eternal 
advantage  of  science,  and  to  the  benefit  of 
mankind,  it  no  longer  invents  a  horror  vacvi, 
a  quinta  essentia,  in  order  to  furnish  credu- 
lous hearers  with  solutions  and  explanations 


CHEMICXAL   CHANGES. 


of  phenomena,  whose  true  connection  with 
others,  whose  ultimate  cause  is  still  un- 
known. 

If  we  assume  that  al1  the  phenomena  ex- 
hibited by  the  organism  of  plants  and  ani- 
mals are  to  be  ascribed  to  a  peculiar  cause, 
different  in  its  manifestations  from  all  other 
causes  which  produce  motion  or  change  of 
condition ;  if,  therefore,  we  regard  the  vital 
force  as  an  independent  force,  then,  in  the 
phenomena  of  organic  life,  as  in  all  other 
phenomena  ascribed  to  the  action  of  forces, 
we  have  the  statics,  that  is,  the  state  of  equi- 
librium determined  by  a  resistance,  and  the 
dynamics,  of  the  vital  force. 

All  the  parts  of  the  animal  body  are  pro- 
duced from  a  peculiar  fluid,  circulating  in 
its  organism,  by  virtue  of  an  influence  resid- 
ing in  every  cell,  in  every  organ,  or  part  of 
an  organ.  Physiology  teaches  that  all  parts 
of  the  body  were  originally  blood ;  or  that 
at  least  they  were  brought  to  the  growing 
organs  by  means  of  this  fluid. 

The  most  ordinary  experience  farther 
shows,  that  at  each  moment  of  life,  in  the 
animal  organism,  a  xamimifid,. Change  of 
matter,  more  or  less  accelerated,  is  going 
on  ;  that  a  part  of  the  structure  is  transformed 
into  unorganized  matter,  loses  its  condition 
of  life,  and  must  be  again  renewed.  Physi- 
ology has  sufficiently  decisive  grounds  for 
the  opinion,  that  every  motion,  every  mani- 
festation of  force,  is  the  result  of  a  transfor- 
mation of  the  structure  or  of  its  substance; 
that  every  conception,  every  mental  affec- 
tion, is  followed  by  changes  in  the  chemical 
nature  of  the  secreted  fluids;  that  every 
thought,  every  sensation,  is  accompanied  by 
a  change  in  the  composition  of  the  sub- 
stance of  the  brain. 

In  order  to  keep  up  the  phenomena  of  life 
in  animals,  certain  matters  are  required 
parts  of  organisms,  which  we  call  nourish- 
ment. In  consequence  of  a  series  of  altera- 
tions, they  serve  either  for  the  increase  o 
the  mass  (nutrition ,)  or  for  the  supply  o 
the  matter  consumed  (reproduction,)  or 
finally,  for  the  production  of  force. 

II.  If  the  first  condition  of  animal  life  b< 
the  assimilation  of  what  is  commonly  callec 
lourishment,  the  second  is  a  continual 
absorption  of  oxygen  from  the  atmos- 
phere. 

Viewed  as  an  object  of  scientific  research, 
animal   life   exhibits   itself  in   a   series  of 
phenomena,  the  connection  and  recurrence 
of  which  are  determined  by  the  changes 
which  the  food  and  the   oxygen  absorbed 
from  the  atmosphere  undergo  in  the  organ- 
ism under  the  influence  of  the  vital  force. 
kAll  vital  activity  arises  from  the  mutual 
lion  of  the  oxygen  of  the  atmosphere  and 
e  elements  of  the  food. 
In  the  processes  of  nutrition  and  repro- 
duction, we  perceive  the  passage  of  matter 
from  the  state   of  motion  to   that   of  rest 
(static  equilibrium ;)  under  the  influence  of 
die  nervous  system,  this  matter  enters  again 
into  a  ,«tate  of  motion.     The  ultimate  causes 


f  these  different  conditions  or  tne  vital  force 
are  chemical  forces. 

The  cause  of  the  state  of  rest  is  a  resist- 
ance, determined  by  a  force  of  attraction 
(combination,)  which  acts  between  the 
smallest  particles  of  matter,  and  is  mani- 
'ested  only  when  these  are  in  actual  contact, 
or  at  infinitely  small  distances. 

To  this  peculiar  kind  of  attraction  we 
may  of  course  apply  different  names ;  but 
the  chemist  calls  it  affinity. 

The  cause  of  the  state  of  motion  is  to  be 
found  in  a  series  of  changes  which  the  food 
undergoes  in  the  organism,  and  these  are 
the  results  of  processes  of  decomposition,  to 
which  either  the  food  itself,  or  the  structures 
formed  from  it,  or  parts  of  organs,  are  sub- 
jected. 

The  distinguishing  character  of  vegetable 
life  is  a  continued  passage  of  matter  fromj 
the  state  of  motion  to  that  of  static  equili  J 
brium.  While  a  plant  lives,  we  cannot 
perceive  any  cessation  in  its  growth ;  no 
part  of  an  organ  in  the  plant  diminishes  in 
size.  If  decomposition  occur,  it  is  the  re- 
sult of  assimilation.  A  plant  produces 
within  itself  no  cause  of  motion ;  no  part 
of  its  structure,  from  any  influence  residing 
in  its  organism,  loses  its  .state  of  vitality, 
and  is  converted  into  unorganized,  amor- 
phous compounds ;  in  a  word,  no  waste 
occurs  in  vegetables.  Waste,  in  the  animal 
body,  is  a  change  in  the  state  or  in  the 
composition  of  some  of  its  parts,  and  conse- 
quently is  the  result  of  chemical  actions. 

The  influence  of  poisons  and  of  remedial 
agents  on  the  living  animal  body  evidently 
shows  that  the  chemical  decompositions  and 
combinations  in  the  body,  which  manifest 
themselves  in  the  phenomena  of  vitality, 
may  be  increased  in  intensity  by  chemical 
forces  of  analogous  character,  and  retarded 
or  put  an  end  to  by  those  of  opposite  cha- 
racter ;  and  that  we  are  enabled  to  exercise 
an  influence  on  every  part  of  an  organ  by 
means  of  substances  possessing  a  well- 
defined  chemical  action. 

As,  in  the  closed  galvanic  circuit,  in  con- 
sequence of  certain  changes  which  an  inor- 
ganic body,  a  metal,  undergoes  when  placed 
in  contact  with  an  acid,  a  certain  something 
becomes  cognizable  by  our  senses,  which 
we  call  a  current  of  electricity ;  so,  in  the 
animal  body,  in  consequence  of  transforma- 
tions and  changes  undergone  by  matter 
previously  constituting  a  part  of  the  organ- 
ism, certain  phenomena  of  motion  and 
activity  are  perceived,  and  these  we  call 
life,  or  vitality. 

The  electrical  current  manifests  Itself  in 
certain  phenomena  of  attraction  and  repul- 
sion, which  it  excites  in  other  bodies  na- 
turally motionless,  and  by  the  phenomena 
of  the  formation  and  decomposition  of  che- 
mical compounds,  which  occur  every  where, 
when  the  resistance  is  not  sufficient  to  arrest 
the  current. 

It  is  from  this  point  of  view,  and  from  no 
other,  that  chemistrv  ought  to  contemplate 
'B 


14 


ANIMAL  CHEMISTRY. 


the  phenomena  of  life.  Wonders  surround 
us  on  every  side.  The  formation  of  a 
crystal,  of  an  octahedron,  is  not  less  incom- 
prehensible than  the  production  of  a  leaf  or 
of  a  muscular  fibre;  and  the  production 
of  vermilion  from  mercury  and  sulphur  is 
as  much  aa  enigma  as  the  formation  of  an 
eye  from  the  substance  of  the  blood. 

The  first  conditions  of  animal  life  are  nu- 
tritious matters  and  oxygen,  introduced  into 
the  system. 

At  every  moment  of  his  life  man  is  taking 
oxygen  into  his  system,  by  means  of  the 
organs  of  respiration  ;  no  pause  is  observ- 
able while  life  continues. 

The  observations  of  physiologists  have 
shown  that  the  body  of  an  adult  man,  sup- 
plied with  sufficient  food,  has  neither  in- 
creased nor  diminished  in  weight  at  the  end 
of  twenty-four  hours ;  yet  the  quantity  of 
oxygen  taken  into  the  system  during  this 
period  is  very  considerable. 

According  to  the  experiments  of  Lavoisier, 
an  adult  man  takes  into  his  system,  from  the 
atmosphere,  in  one  year,  746  Ibs.,  according 
to  Menzies,  837  Ibs.' of  oxygen;  yet  we  find 
his  weight,  at  the  beginning  and  end  of  the 
year,  either  quite  the  same,  or  differing, 
one  way  or  the  other,  by  at  most  a  few 
pounds.  (1)* 

What,  k  may  be  asked,  has  become  of 
the  enormous  weight  of  oxygen  thus  intro- 
duced, in  the  course  of  a  year  into  the 
hi  man  system? 

This  question  may  be  answered  satisfac- 
torily ;  no  part  of  this  oxygen  remains  in  the 
system ;  but  it  is  given  out  again  in  the  form 
of  a  compound  of  carbon  or  of  hydrogen. 

The  carbon  and  hydrogen  of  certain  parts 
of  the  body  have  entered  into  combination 
with  the  oxygen  introduced  through  the 
lungs  and  through  the  skin,  and  have  been 
give.n  out  in  the  forms  of  carbonic  acid  gas 
and  the  vapour  of  water. 

At  every  moment,  with  every  expiration, 
certain  quantities  of  its  elements  separate 
from  the  animal  organism,  after  having  en- 
tered into  combination,  within  the  body, 
with  the  oxygen  of  the  atmosphere. 

If  we  assume,  with  Lavoisier  and  Seguin, 
in  order  to  obtain  a  foundation  for  our  cal- 
culation, that  an  adult  man  receives  into  his 
system  daily  32£oz.  (46,037  cubic  inches= 
15,661  grains,  French  weight)  of  oxygen, 
and  that  the  weight  of  the  whole  mass  of 
his  blood,  of  which  80  per  cent,  is  water,  is 
24  Ibs. ;  it  then  appears,  from  the  known 
composition  of  the  blood,  that,  in  order  to 
convert  the  whole  of  its  carbon  and  hydro- 
gen into  carbonic  acid  and  water,  64,103 
grains  of  oxygen  are  required.  This  quan- 
tity will  be  taken  into  the  system  of  an  adult 
in  four  days  five  hours.  (2) 

Whether  this  oxygen  enters  into  combi- 
nation with  the  elements  of  the  blood,  or 
with  other,  parts  of  the  body  containing  car- 
bon and  hydrogen,  in  either  case  the  conclu- 


*  The  Numbers  refer  to  the  Appendix. 


sion  is  inevitable,  that  the  body  of  a  man 
who  daily  takes  into  the  system  32^  oz.  of 
oxygen,  must  receive  daily  in  the  shape  of 
nourishment,  as  much  carbon  and  hydrogen 
as  would  suffice  to  supply  24  Ibs.  of  blood 
with  these  elements;  it  being  presupposed 
that  the  weight  of  the  body  remains  un- 
changed, and  that  it  retains  its  normal  con- 
dition as  to  health. 

This  supply  is  furnished  in  the  food. 

From  the  accurate  determination  of  the 
quantity  of  carbon  daily  taken  into  the  sys- 
tem in  the  food,  as  well  as  of  that  propor- 
tion of  it  which  passes  out  of  the  body  in 
the  faeces  and  urine,  unburned,  that  is,  in 
some  form  in  which  it  is  not  combined  with 
oxygen,  it  appears  that  an  adult,  taking 
moderate  exercise,  consumes  13.9  oz.  of 
carbon  daily.  (3) 

These  13^%  oz.  of  carbon  escape  through 
the  skin  and  lungs  as  carbonic  acid  gas. 

For  conversion   into  carbonic  acid   gas, 
oz.  of  carbon  require  37  oz.  of  oxygen. 

According  to  the  analyses  of  Boussingault 
(Ann.  de  Ch.  et  de  Ph.  LXXI.  p.  136)  a 
horse  consumes  in  twenty-four  hours  97£ 
oz.  of  carbon,  a  milk  cow  69^  oz.  The 
quantities  of  carbon  here  mentioned  are 
those  given  off  from  the  bodies  of  these  ani- 
mals in  the  form  of  carbonic  acid ;  and  it 
appears  from  them  that  the  horse  consumes, 
in  converting  carbon  into  carbonic  acid,  13 
Ibs.  3J  oz.  in  twenty-four  hours,  and  the 
milk  cow  11  Ibs.  10|  oz.  of  oxygen  in  the 
same  time.  (4) 

Since  no  part  of  the  oxygen  taken  into 
the  system  is  again  given  off  in  any  otner 
form  but  that  of  a  compound  of  carbon  or 
hydrogen;  since,  farther,  the  carbon  and  hy- 
drogen given  off  are  replaced  by  carbon  and 
hydrogen  supplied  in  the  food,  it  is  clear 
that  the  amount  of  nourishment  required  by 
the  animal  body  must  be  in  a  direct  ratio  to 
the  quantity  of  oxygen  taken  into  the 
system. 

Two  animals,  which  in  equal  times  take 
up  by  means  of  the  lungs  and  skin  unequal 
quantities  of  oxygen,  consume  quantities  of 
the  same  nourishment  which  are  unequal  in 
the  same  ratio. 

The  consumption  of  oxygen  in  equal 
times  may  be  expressed  by  the  number  of 
respirations ;  it  is  clear  that,  in  the  same  in 
dividual,  the  quantity  of  nourishment  re- 
quired mus-t  vary  with  the  force  and  num  • 
ber  of  the  respirations. 

A  child,  in  whom  the  organs  of  respiration 
are  naturally  very  active,  requires  food  uf- 
tener  than  an  adult,  and  bears  hunger  less 
easily.  A  bird,  deprived  of  food,  dies  on  the 
third  day,  while  a  serpent,  with  its  sluggish 
respiration,  can  live  without  food  three 
months  and  longer. 

The  number  of  respirations  is  smaller  m 
a  state  of  rest  than  during  exercise  or  work. 
The  quantity  of  food  necessary  in  both  con- 
ditions must  vary  in  the  same  latio. 

An  excess  of  food  is  incompatible  with 
deficiency  in  respired  oxygen,  that  is,  with 


SOURCE   OF   ANIMAL   HEAT.— RESPIRATION. 


15 


deficient  exercise;  just  as  violent  exercise, 
which  implies  an  increased  supply  of  food, 
is  incompatible  with  weak  digestive  organs. 
In  either  case  the  health  suffers. 

But  the  quantity  of  oxygen  inspired  is 
also  affected  by  the  temperature  and  density 
of  the  atmosphere. 

The  capacity  of  the  chest  in  an  animal  is 
a  constant  quantity.  At  every  respiration  a 
quantity  of  air  enters,  the  volume  of  which 
may  be  considered  as  uniform;  but  its 
weight,  and  consequently  that  of  the  oxygen 
it  contains,  is  not  constant.  Air  is  expanded 
by  heat,  and  contracted  by  cold,  and  there- 
fore equal  volumes  of  hot  and  cold  air  con- 
lain  unequal  weights  of  oxygen.  In  sum- 
mer, moreover,  atmospherical  air  contains 
aqueous  vapour,  while  in  winter  it  is  dry; 
the  space  occupied  by  vapour  in  the  warm 
air  is  filled  up  by  air  itself  in  winter ;  that 
is,  it  contains,  for  the  same  volume,  more 
oxygen  in  winter  than  in  summer. 

In  summer  and  in  winter,  at  the  pole 
and  at  the  equator,  we  respire  an  equal  vo- 
lume of  air ;  the  cold  air  is  warmed  during 
respiration,  and  acquires  the  temperature  of 
the  body.  To  introduce  into  the  lungs  a 
given  volume  of  oxygen,  less  expenditure 
of  force  is  necessary  in  winter  than  in  sum- 
mer ;  and  for  the  same  expenditure  of  force, 
more  oxygen  is  inspired  in  winter. 

It  is  obvious,  that  in  an  equal  number  of 
respirations  we  consume  more  oxygen  at 
the  level  of  the  sea  than  on  a  mount.vin. 
The  quantity  both  of  oxygen  inspired  and 
of  carbonic  acid  expired,  must,  therefore, 
vary  with  the  height  of  the  barometer. 

The  oxygen  taken  into  the  system  is  given 
out  again  in  the  same  forms,  whether  in 
summer  or  in  winter;  hence  we  expire 
more  carbon  in  cold  weather,  and  when  the 
barometer  is  high,  than  we  do  in  warm 
weather;  and  we  must  consume  more  or 
less  carbon  in  our  food  in  the  same  propor- 
tion;  in  Sweden  more  than  in  Sicily;  and 
in  our  more  temperate  climate  a  full  eighth 
more  in  winter  than  in  summer. 

Even  when  we  consume  equal  weights 
of  food  in  cold  and  warm  countries,  infinite 
wisdom  has  so  arranged,  that  the  articles  of 
food  in  different  climates  are  most  unequal 
in  the  proportion  of  carbon  they  contain. 
The  fruits  on  which  the  natives  of  the 
south  prefer  to  feed  do  not  in  the  fresh  state 
contain  more  than  12  per  cent,  of  carbon, 
while  the  bacon  and  train  oil  used  by  the 
inhabitants  of  the  arctic  regions  contain 
from  66  to  80  per  cent,  of  carbon. 

It  is  no  difficult  matter,  in  warm  climates, 
to  study  moderation  in  eating,  and  men  can 
bear  hunger  for  a  long  time  under  the  equa- 
tor; but  cold  and  hunger  united  very  soon 
exhaust  the  body. 

The  mutual  action  between  the  elements 
of  the  food  and  the  oxygen  conveyed  by  the 
circulation  of  the  blood  to  every  part  of  the 
body  is  THE  SOURCE  OF  ANIMAL  HEAT, 

III.  All  living  creatures,  whose  existence 
depends  on  the  absorption  of  oxygen,  pos- 


sess within  themselves  a  source  of  heat  in- 
dependent of  surrounding  objects. 

This  truth  applies  to  all  animals,  and  ex- 
tends, besides,  to  the  germination  of  seeds, 
to  the  flowering  of  plants,  and  to  the  matura- 
tion of  fruits. 

It  is  only  in  those  parts  of  the  body*  to 
which  arterial  blood,  and  with  it  the  oxygen 
absorbed  in  respiration,  is  conveyed,  that 
heat  is  produced.  Hair,  wool,  or  feathers, 
do  not  possess  an  elevated  temperature. 

This  high  temperature  of  the  animal 
body,  or,  as  it  may  be  called,  disengagement 
of  heat,  is  uniformly  and  under  all  circum- 
stances the  result  of  the  combination  of  a 
combustible  substance  with  oxygen. 

In  whatever  way  carbon  may  combine 
with  oxygen,  the  act  of  combination  cannot 
take  place  without  the  disengagement  of 
heat.  It  is  a  matter  of  indifference  whether 
the  combination  take  place  rapidly  or  slowly, 
at  a  high  or  at  a  low  temperature:  the 
amount  of  heat  liberated  is  a  constant 
quantity. 

The  carbon  of  the  food,  which  is  con- 
verted into  carbonic  acid  within  the  body, 
must  give  out  exactly  as  much  heat  as  if  it 
had  been  directly  burnt  in  the  air  or  in  oxy- 
gen gas;  the  only  difference  is,  that  the 
amount  of  heat  produced  is  diffused  over 
unequal  times.  In  oxygen,  the  combustion 
is  more  rapid,  and  the  heat  more  intense ; 
in  air  it  is  slower,  the  temperature  is  not  so 
high,  but  it  continues  longer. 

It  is  obvious  that  the  amount  of  heat  libe- 
rated must  increase  or  diminish  with  the 
quantity  of  oxygen  introduced  in  equal 
times  by  respiration.  Those  animals  which 
respire  frequently,  and  consequently,  con- 
sume much  oxygen,  possess  a  higher  tem- 
perature than  others,  which,  with  a  body  of 
equal  size  to  be  heated,  take  into  the  system 
less  oxygen.  The  temperature  of  a  child 
(102°)  is  higher  than  that  of  an  adult 
(99-50).  That  ot  birds  (104°  to  105-40)  is 
higher  than  that  of  quadrupeds  (98-5°  to 
100-4°)  or  than  that  of  fishes  or  amphibia, 
whose  proper  temperature  is  from  27°  to 
3"6°  higher  than  that  of  the  medium  in 
which  they  live.  All  animals,  strictly 
speaking  are  warm-blooded  ;  but  in  those 
only  which  possess  lungs  is  the  temperature 
of  the  body  quite  independent  of  the  sur- 
rounding medium.  (5) 

The  most  trustworthy  observations  prove 
that  in  all  climates,  in  the  temperate  zones 
as  well  as  at  the  equator  or  the  poles,  the 
temperature  of  the  body  in  man,  and  in 
what  are  commonly  called  warm-blooded 
animals,  is  invariably  the  same ;  yet  how 
different  are  the  circumstances  under  which 
they  live ! 

The  animal  body  is  a  heated  mass,  which 
bears  the  same  relation  to  surrounding  ob- 
jects as  any  other  heated  mass.  It  receives 
heat  when  the  surrounding  objects  are  hotter, 
it  loses  heat  when  they  are  colder  than 
itself. 

We  know  that  the  rapidity  of  cooling  in 


10 


ANIMAL   CHEMISTRY. 


creases  with  the  difference  between  the  tern-  | 
perature  of  the  heated  body  and  that  of  the  } 
surrounding  medium ;  that  is,  the  colder  the  | 
surrounding  medium  the  shorter  the  time 
required  for  the  cooling  of  the  heated  body. 

How  unequal,  then,  must  be  the  loss  of 
heat  in  a  maa  at  Palermo,  where  the  exter- 
nal temperature  is  nearly  equal  to  that  of  the 
body,  and  in  the  polar  regions,  where  the 
external  temperature  is  from  70°  to  90° 
lower. 

Yet,  notwithstanding  this  extremely  un- 
equal loss  of  heat,  experience  has  shown 
that  the  blood  of  the  inhabitant  of  the  arctic 
circle  has  a  temperature  as  high  as  that  of 
the  native  of  the  south,  who  lives  in  so  dif- 
ferent a  medium. 

This  fact,  when  its  true  significance  is  per- 
ceived, proves  that  the  heat  given  off  to  the 
surrounding  medium  is  restored  within  the 
Body  with  great  rapidity.  This  compensa- 
tion takes  place  more  rapidly  in  winter  than 
in  summer,  at  the  pole  than  at  the  equator. 

Now,  in  different  climates  the  quantity  of 
oxygen  introduced  into  the  system  of  respi- 
ration, as  has  been  already  shown,  varies 
according  to  the  temperature  of  the  exter- 
nal air ;  the  quantity  of  inspired  oxygen  in- 
creases with  the  loss  of  heat  by  external 
cooling,  and  the  quantity  of  carbon  or  hydro- 
gen necessary  to  combine  with  this  oxygen 
must  be  increased  in  the  same  ratio. 

It  is  evident  that  the  supply  of  the  heat 
iost  by  cooling  is  effected  by  the  mutual 
action  of  the  elements  of  the  food  and  the 
inspired  oxygen,  which  combine  together. 
To  make  use  of  a  familiar,  but  not  on  that 
account  a  less  just  illustration,  the  animal 
body  acts,  in  this  respect,  as  a  furnace, 
which  we  supply  with  fuel.  It  signifies 
nothing  what  intermediate  forms  food  may 
assume,  what  changes  it  may  undergo  in  the 
body,  the  last  change  is  uniformly  the  con- 
version of  its  carbon  into  carbonic  acid,  and 
qf  its  hydrogen  into  water;  the  unassimila- 
ted  nitrogen  of  the  food,  along  with  the  un- 
burned  or  unoxidised  carbon,  is  expelled  in 
the  urine  or  in  the  solid  excrements.  In 
order  to  keep  up  in  the  furnace  a  constant 
temperature,  we  must  vary  the  supply  of 
fuel  according  to  the  external  temperature, 
that  is,  according  to  the  supply  of  oxygen. 

In  the  animal  body  the  food  is  the  fuel ; 
with  a  proper  supply  of  oxygen  we  obtain 
the  heat  given  out  during  its  oxidation  or 
combustion.  In  winter,  when  we  take 
exercise  in  a  cold  atmosphere,  and  when 
consequently,  the  amount  of  inspired  oxygen 
increases,  the  necessity  for  food  containing 
carbon  and  hydrogen  increases  in  the  same 
ratio;  and  by  gratifying  the  appetite  thus 
excited,  we  obtain  the  most  efficient  protec- 
tion against  the  most  piercing  cold.  A 
starving  man  is  soon  frozen  to  death ;  and 
every  one  knows  that  the  animals  of  prey 
in  the  arctic  regions  far  exceed  in  voracity 
those  of  the  torrid  zone. 

In  cold  and  temperate  climates,  the  air, 
which  incessantly  strives  to  consume  the 


body,  urges  man  to  labourious  eflorts  in 
order  to  furnish  the  means  of  resistance  to 
its  action,  while,  in  hot  climates,  the  neces- 
sity of  labour  to  provide  food  is  far  less 
urgent. 

Our  clothing  is  merely  an  equivalent  for 
a  certain  amount  of  food.  The  more  warmly 
we  are  clothed  the  less  urgent  becomes  the 
appetite  for  food,  because  the  loss  of  heat 
by  cooling,  and  consequently  the  amount 
of  heat  to  be  supplied  by  the  food,  is  di- 
minished. 

If  we  were  to  go  naked,  like  certain  savage 
tribes,  or  if  in  hunting  or  fishing  we  were 
exposed  to  the  same  degree  of  cold  as  the 
Samoyedes,  we  should  be  able  with  ease  to 
consume  10  Ibs.  of  flesh,  and  perhaps,  a 
dozen  of  tallow  candles  into  the  bargain, 
daily,  as  warmly  clad  travellers  have  re- 
lated with  astonishment  of  these  people! 
We  should,  then,  also  be  able  to  take  the 
same  quantity  of  brandy  or  train  oil  without 
bad  effects,  because  the  carbon  and  hydrogen 
of  these  substances  would  only  suffice  to 
keep  up  the  equilibrium  between  the  exter- 
nal temperature  and  that  of  our  bodies. 

According  to  the  preceding  expositions, 
the  quantity  of  food  is  regulated  by  the 
number  of  respirations,  by  the  temperature 
of  the  air,  and  by  the  amount  of  heat  given 
off  to  the  surrounding  medium. 

No  isolated  fact,  apparently  opposed  to 
this  statement,  can  affect  the  truth  of  this 
natural  law.  Without  temporary  or  perma- 
nent injury  to  health,  the  Neapolitan  cannot 
take  more  carbon  and  hydrogen  in  the  shape 
of  food  than  he  expires  as  carbonic  acid 
and  water ;  and  the  Esquimaux  cannot  ex- 
pire more  carbon  and  hydrogen  than  he 
takes  into  the  system  as  food,  unless  in  a 
state  of  disease  or  of  starvation.  Let  us  ex- 
amine these  states  a  little  more  closely. 

The  Englishman  in  Jamaica  sees  with 
regret  the  disappearance  of  his  appetite, 
previously  a  source  of  frequently  recurring 
enjoyment ;  and  he  succeeds  by  the  use  of 
cayenne  pepper  and  the  most  powerful 
stimulants,  in  enabling  himself  to  take  as 
much  food  as  he  was  accustomed  to  eat  at 
home.  But  the  whole  of  the  carbon  thus 
introduced  into  the  system  is  not  consumed; 
the  temperature  of  the  air  is  too  high,  and 
the  oppressive  heat  does  not  allow  him  to 
increase  the  number  of  respirations  by  active 
exercise,  and  thus  to  proportion  the  waste 
to  the  amount  of  food  taken;  disease  of 
some  kind,  therefore,  ensues. 

On  the  other  hand,  England  sends  her 
sick,  whose  diseased  digestive  organs  have 
in  a  greater  or  less  degree  lost  the  power  of 
bringing  the  food  into  that  state  in  which  it 
is  best  adapted  for  oxidation,  and  therefore, 
furnish  less  resistance  to  the  oxidising 
agency  of  the  atmosphere  than  is  required 
in  their  native  climate,  to  southern  regions 
where  the  amount  of  inspired  oxygen  is 
diminished  in  so  great  a  proportion;  and 
the  result,  an  improvement  in  the  health, 
is  obvious.  The  diseased  organs  of  diges- 


EFFECTS   OF   STARVATION. 


17 


tion  hiure  sufficient  power  to  place  the  di- 
minished amount  of  food  m  equilibrium 
with  the  inspired  oxygen ;  in  the  colder 
climate,  the  organs  of  respiration  them- 
selves would  have  been  consumed  in  fur- 
nishing the  necessary  resistance  to  the  action 
of  the  atmospheric  oxygen. 

In  our  climate,  hepatic  diseases,  or  those 
arising  from  excess  of  carbon,  prevail  in 
summer;  in  winter,  pulmonic  diseases,  or 
tho^e  arising  from  excess  of  oxygen,  are 
more  frequent. 

The  cooling  of  the  body,  by  whatever 
cause  it  may  be  produced,  increases  the 
amount  of  food  necessary.  The  mere  ex- 
posure to  the  open  air,  in  a  carriage  or  on 
the  deck  of  a  ship,  by  increasing  radiation 
and  vaporization,  increases  the  loss  of  heat, 
and  compels  us  to  eat  more  than  usual. 
The  same  is  true  of  those  who  are  accus- 
tomed to  drink  large  quantities  of  cold 
water,  which  is  given  off*  at  the  temperature 
of  the  body,  98-5°.  It  increases  the  appe- 
tite, and  persons  of  weak  constitution  find 
it  necessary,  by  continued  exercise,  to  sup- 
ply to  the  sysiem  the  oxygen  required  to 
restore  the  heat  abstracted  by  the  cold 
water.  Loud  and  long  continued  speaking, 
the  crying  uf  infants,  moist  air,  all  exert  "a 
decided  and  appreciable  influence  on  the 
amount  of  food  which  is  taken. 

IV.  In  the  foregoing  pages,  it  has  been 
assumed  that  it  is  especially  carbon  and 
hydrogen  which,  by  combining  with  oxy- 
gen, serve  t6  produce  animal  heat.  In  fact, 
observation  proves  that  the  hydrogen  of  the 
food  plays  a  not  less  important  part  than  the 
carbon. 

The  whole  process  of  respiration  appears 
most  clearly  developed,  when  we  consider 
the  state  of  a  man,  or  other  animal,  totally 
deprived  of  food. 

The  first  effect  of  starvation  is  the  disap- 
pearance of  fat,  and  this  fat  cannot  be  traced 
in  the  urine  or  in  the  scanty  faeces.  Its  car- 
bon and  hydrogen  have  been  given  off 
through  the  skin  and  lungs  in  the  form  of 
oxidised  products ;  it  is  obvious  that  they 
have  served  to  support  respiration. 

In  the  case  of  a  starving  man,  32£  oz.  of 
oxygen  enter  the  system  daily,  and  are 
given  out  again  in  combination  with  a  part 
of  his  body.  Currie  mentions  the  case  of 
an  individual  who  was  unable  to  swallow, 
and  whose  body  lost  100  Ibs.  in  weight  dur- 
ing a  month;  and,  accordiag  to  Martell 
(Trans.  Linn.  Soc.,  vol.  xi.  p.  411,)  a  fat 
pig,  overwhelmed  in  a  slip  of  earth,  lived 
160  days  without  food,  and  was  found  to 
have  diminished  in  weight,  in  that  time, 
more  than  120  Ibs.  The  whole  history  of 
hybernating  animals,  and  the  well  esta- 
blished facts  of  the  periodical  accumulation, 
in  various  animals,  of  fat,  which,  at  other 
periods,  entirely  disappears,  prove  that  the 
oxygen,  in  the  respiratory  process,  con- 
sumes, without  exception,  all  such  su  In- 
stances as  are  capable  of  entering  into 
combination  with  it.  It  combines  with 
3 


whatever  js  presented  to  it ,  and  the  defici- 
ency of  hydrogen  is  the  only  reason  why 
carbonic  acid  is  the  chief  product ;  for,  at 
the  temperature  of  the  body,  the  affinity  ol 
hydrogen  for  oxygen  far  surpasses  that  ol 
carbon  for  the  same  element. 

We  know,  in  fact,  that  the  graminivora 
expire  a  volume  of  carbonic  acid  equal  to 
that  of  the  oxygen  inspired,  while  the  carni- 
vora,  the  only  class  of  animals  whose  food 
contains  fat,  inspire  more  oxygen  than  is 
equal  in  volume  to  the  carbonic  acid  ex- 
pired. Exact  experiments  have  shown, 
that  in  many  cases  only  half  the  volume  of 
oxygen  is  expired  in  the  form  of  carbonic 
acid.  These  observations  cannot  be  gain- 
said, and  are  far  more  convincing  than  those 
arbitrary  and  artificially  produced  pheno- 
mena, sometimes  called  experiments  ;  expe- 
riments which,  made  as  too  often  they  are, 
without  regard  to  the  necessary  and  natural 
conditions,  possess  no  value,  and  may  be 
entirely  dispensed  with  ;  especially  when,  as 
in  the  present  case,  nature  affords  the  op- 
portunity for  observation,  and  when  we 
make  a  rational  use  of  that  opportunity. 

In  the  progress  of  starvation,  however,  if 
is  not  only  the  fat  which  disappears,  but 
also,  by  degrees,  all  such  of  the  solids  as 
are  capable  of  being  dissolved.  In  the 
wasted  bodies  of  those  who  have  suffered 
starvation,  the  muscles  are  shrunk  and  un- 
naturally soft,  and  have  lost  their  contracti- 
lity ;  all  those  parts^of  the  body  which  were 
capable  of  entering  into  the  state  of  motion, 
have  served  to  protect  the  remainder  of  the 
frame  from  the  destructive  influence  of  the 
atmosphere.  Towards  the  end,  the  parti- 
cles of  the  brain  begin  to  undergo  the  process 
of  oxidation,  and  delirium,  mania,  and  death 
close  the  scene ;  that  is  to  say,  all  resistance 
to  the  oxidising  power  of  the  atmospheric 
oxygen  ceases,  and  the  chemical  process  ol 
eremacausis,  or  decay,  commences,  in  which 
every  part  of  the  body,  the  bones  excepted, 
enters  into  combination  with  oxygen. 

The  time  which  is  required  to  cause  death 
by  starvation  depends  on  the  amount  of  fat 
in  the  body,  on  the  degree  of  exercise,  as  in 
labour  or  exertion  of  any  kind,  on  the  tem- 
perature of  the  air,  and  finally,  on  the  pre- 
sence or  absence  of  water.  Through  the 
skin  and  lungs  there  escapes  a  certain  qiian 
tity  of  water,  and  as  the  presence  of  water 
is  essential  to  the  continuance  of  the  vital 
motions,  its  dissipation  hastens  death.  Cases 
have  occurred,  in  which  a  full  supply  of 
water  being  accessible  to  the  sufferer,  death 
has  not  occurred,  till  after  the  lapse  of 
twenty  days.  In  one  case,  life  was  sus- 
tained in  this  way  for  the  period  of  sixty 
days. 

In  all  chronic  diseases  death  is  produced 
by  the  same  cause,  namely,  the  chemical 
action  of  the  atmosphere.  When  those 
substances  are  wanting;  whose  function  in 
the  organism  is  to  support  the  process  of 
respiration;  when  the  diseased  organs  are 
incapable  of  performing  their  proper  func- 


18 


ANIMAL   CHEMISTRY. 


ton  of  producing  these  substances;  when 
they  have  lost  the  power  of  transforming 
the  food  into  that  shape  in  which  it  may, 
by  entering  into  combination  with  the  oxy- 
gen ol  the  air,  protect  the  system  from  its 
influence,  then,  the  substance  of  the  organs 
themselves,  the  fat  of  the  body,  the  sub- 
stance of  the  muscles,  the  nerves,  and  the 
brain,  are  unavoidably  consumed.* 

The  true  cause  of  death  in  these  cases  is 
the  respiratory  process,  that  is,  the  action  of 
the  atmosphere. 

A  deficiency  of  food,  and  the  want  of 
power  to  convert  the  food  into  a  part  of  the 
organism,  are  both,  equally  a  want  of  resist- 
ance ;  and  this  is  the  negative  cause  of  the 
cessation  of  the  vital  process.  The  flame 
is  extinguished,  because  the  oil  is  consumed ; 
and  it  is  the  oxygen  of  the  air  which  has 
consumed  it. 

In  many  diseases  substances  are  produced 
which  are  incapable  of  assimilation.  By 
the  mere  deprivation  of  food,  these  sub- 
stances are  removed  from  the  body  without 
leaving  a  trace  behind ;  their  elements  have 
entered  into  combination  with  the  oxygen 
of  the  air. 

From  the  first  moment  that  the  function 
of  the  lungs  or  of  the  skin  is  interrupted  or 
disturbed,  compounds,  rich  in  carbon,  ap- 
pear in  the  urine,  which  acquires  a  brown 
colour.  Over  the  whole  surface  of  the  body 
oxygen  is  absorbed,  and  combines  with  all 
the  substances  which  offer  no  resistance  to 
it.  In  those  parts  of  the  body  where  the 
access  of  oxygen  is  impeded ;  for  example, 
in  the  armpits,  or  in  the  soles  of  the  feet, 
peculiar  compounds  are  given  out,  recog- 
nisable by  their  appearance,  or  by  their 
odour.  These  compounds  contain  much 
carbon. 

Respiration  is  the  falling  weight,  the  bent 
spring,  which  keeps  the  clock  in  motion ; 
the  inspirations  and  expirations  are  the 
strokes  of  the  pendulum  which  regulate  it. 
In  our  ordinary  timepieces,  we  know  with 
mathematical  accuracy  the  effect  produced 
0*1  their  rate  of  going,  by  changes  in  the 
length  of  the  pendulum,  or  in  the  external 
temperature.  Few,  however,  have  a  clear 
conception  of  the  influence  of  air  and  tem- 
perature on  the  health  of  the  humaa  body ; 
and  yet  the  research  into  the  conditions  ne- 
cessary to  keep  it  in  the  nominal  state,  is  not 
more  difficult  than  in  the  case  of  a  clock. 

V.  The  want  of  a  just  conception  of  force 
and  effect,  and  of  the  connection  of  natural 
phenomena,  has  led  chemists  to  attribute  a 
part  of  the  heat  generated  in  the  animal 
body  to  the  action  of  the  nervous  system. 
If  this  view  exclude  chemical  action,  or 
changes  in  the  arrangement  of  the  elemen- 
tary particles,  as  a  condition  of  nervous 


*  For  an  account  of  what  really  takes  place  in 
this  process,  I  refer  to  the  considerations  on  the 
means  by  which  the  change  of  matter  is  effected 
in  the  body  of  the  carnivora,  which  will  be  found 


agency,  it  means  nothing  else  than  to  derive 
the  presence  of  motion,  the  manifestation  of 
a  force,  from  nothing.  But  no  force,  no 
power  can  come  of  nothing. 

No  one  will  seriously  deny  the  share 
which  the  nervous  apparatus  has  in  the 
respiratory  process ;  for  no  change  of  condi- 
tion can  occur  in  the  body  without  the 
nerves ;  they  are  essential  to  all  vital  motions. 
Under  their  influence,  the  viscera  produce 
those  compounds,  which,  while  they  protect 
the  organism  from  the  action  of  the  oxygen 
of  the  atmosphere,  give  rise  to  animal  heat; 
and  when  the  nerves  cease  to  perform  their 
functions,  the  whole  process  of  the  action 
of  oxygen  must  assume  another  form. 
When  the  pons  Varolii  is  cut  through  in  the 
dog,  or  when  a  stunning  blow  is  inflicted  on 
the  back  of  the  head,  the  animal  continues 
to  respire  for  some  time,  often  more  rapidly 
than  in  the  nominal  state;  the  frequency 
of  the  pulse  at  first  rather  increases  than 
diminishes,  yet  the  animal  cools  as  rapidly 
as  if  sudden  death  had  occurred.  Exactly 
similar  observations  have  been  made  on  the 
cutting  of  the  spinal  chord,  and  of  the  par 
vagum.  The  respiratory  motions  continue 
for  a  time,  but  the  oxygen  does  not  meet 
with  those  substances  with  which,  in  the 
normal  state,  it  would  have  combined ;  be- 
cause the  paralysed  viscera  will  no  longer 
furnish  them.  The  singular  idea  that  the 
nerves  produce  animal  heat,  has  obviously 
arisen  from  the  notion  that  the  inspired  oxy- 
gen combines  with  carbon,  in  the  blood 
itself;  in  which  case  the  temperature  of  the 
body,  in  the  above  experiments,  certainly, 
ought  not  to  have  sunk.  But,  as  we  shall 
afterwards  see,  there  cannot  be  a  more  erro 
neous  conception  than  this. 

As  by  the  division  of  the  pneumogastric 
nerves  the  motion  of  the  stomach  and  the 
secretion  of  the  gastric  juice  are  arrested, 
and  an  immediate  check  is  thus  given  to  the 
process  of  digestion,  so  the  paralysis  of  the 
organs  of  vital  motion  in  the  abdominal  vis- 
cera affects  the  process  of  respiration.  These 
processes  are  most  intimately  connected , 
and  every  disturbance  of  the  nervous  system 
or  of  the  nerves  of  digestion  re-acts  visibly 
on  the  process  of  respiration. 

The  observation  has  been  made,  that  heat 
is  produced  by  the  contraction  of  the  mus- 
cles, just  as  in  a  piece  of  caoutchouc,  which, 
when  rapidly  drawn  out,  forcibly  contracts 
again,  with  disengagement  of  heat.  Some 
have  gone  so  far  as  to  ascribe  a  part  of  the 
animal  heat  to  the  mechanical  motions  of 
the  body,  as  if  these  motions  could  exist 
without  an  expenditure  of  force  consumed 
in  producing  them ;  how  then,  we  may  asu:, 
is  this  force  produced  ? 

By  the  combustion  of  carbon,  by  the  solu- 
tion of  a  metal  in  an  acid,  by  the  combina- 
tion of  the  two  electricities,  positive  and 
negative,  by  the  absorption  of  light,  and  even 
by  the  rubbing  of  two  solid  bodies  together 
with  a  certain  degres  ;£  rapidity,  heat  may 
be  produced. 


GREAT  AMOUNT  OF   ANIMAL   HEAT. 


By  a  number  of  causes,  in  appearance 
entirely  distinct,  we  can  thus  produce  one 
and  the  same  eflect.  In  combustion  and  in 
the  production  of  galvanic  electricity,  we 
have  a  change  of  condition  in  material  par- 
ticles ;  when  heat  is  produced  by  the  ab- 
sorption of  light  or  by  friction,  we  have  the 
conversion  of  one  kind  of  motion  into  an- 
other, wnich  affects  our  senses  differently. 
In  all  such  cases  we  have  a  something 
given,  which  merely  takes  another  form; 
m  all  we  have  a  force  and  its  effect.  By 
means  of  the  fire  which  heats  the  boiler  of  a 
steam  engine  we  can  produce  every  kind 
of  motion,  and  by  certain  amount  of  motion 
we  can  produce  fire. 

When  we  rub  a  piece  of  sugar  briskly  on 
an  iron  grater,  it  undergoes,  at  the  surfaces 
of  contact,  the  same  change  as  if  exposed 
to  heat;  and  two  pieces  of  ice,  when  rubbed 
together,  melt  at  the  point  of  contact. 

Let  us  remember  that  the  most  distin- 
guished authorities  in  physics  consider  the 
phenomena  of  heat  as  phenomena  of  motion, 
because  the  very  conception  of  the  creation 
of  matter,  even  though  imponderable,  is  ab- 
solutely irreconcilable  with  its  production 
by  mechanical  causes,  such  as  friction  or 
motion. 

But,  admitting  all  the  influence  which 
electric  or  magnetic  disturbances  in  the  ani- 
mal body  can  have  on  the  functions  of  its 
organs,  still  the  ultimate  cause  of  all  these 
forces  is  a  change  of  condition  in  material 
particles,  which  may  be  expressed*  by  the 
conversion,  within  a  certain  time,  of  the  ele- 
ments of  the  food  into  oxidised  products. 
Such  of  these  elements  as  do  not  undergo 
this  process  of  slow  combustion,  are  given 
off  unburned  or  incombustible  in  the  exe- 
crements. 

Now,  it  is  absolutely  impossible  that  a 
given  amount  of  carbon  or  hydrogen,  what- 
ever different  forms  they  may  assume  in  the 
progress  of  the  combustion,  can  produce 
more  heat  than  if  directly  burned  into  atmos- 
pheric air  or  in  oxygen  gas. 

When  we  kindle  a  fire  under  a  steam 
engine,  and  employ  the  power  obtained  to 
produce  heat  by  friction,  it  is  impossible 
that  the  heat  thus  obtained  can  ever  be 
greater  than  that  which  was  required  to 
heat  the  boiler ;  and  if  we  use  the  galvanic 
current  to  produce  heat,  the  amount  of  heat 
obtained  is  never  in  any  circumstances, 
greater  than  we  might  have  by  the  com- 
bustion of  the  zinc  which  has  been  dissolved 
:ji  the  acid. 

The  contraction  of  muscles  produces  heat; 
but  the  force  necessary  for  the  contraction 
Ins  mini  Tested  itself  through  the  organs  of 
motion,  in  which  it  has  been  excited  by 
chemical  changes.  The  ultimate  cause  of 
the  heat  produced  is,  therefore,  to  be  found  in 
these  chemical  changes. 

By  dissolving  a  metal  in  an  acid,  we 
produc^  an  electrical  current ;  this  current, 
if  passed  through  a  wire,  converts  the  wire 
»p«^  a  magnet,  by  means  of  which,  many 


different  effects  may  be  produced.  The 
cause  of  this  phenomena  is  magnetism ;  the 
cause  of  the  magnetic  phenomena  is  to  be 
found  in  the  electrical  current ;  and  the  ulti- 
mate cause  of  the  electrical  current  is  found 
to  be  a  chemical  change,  a  chemical  action. 

There  are  various  causes  by  which  force 
or  motion  may  be  produced.  A  bent  spring, 
a  current  of  air,  the  fall  of  water,  fire  ap- 
plied to  a  boiler,  the  solution  of  a  metal  in 
an  acid, — all  these  different  causes  of  mo- 
tion may  be  made  to  produce  the  same 
effect.  But  in  the  animal  body  we  recog- 
nise as  the  ultimate  cause  of  all  force  only 
one  cause,  the  chemical  action  which  the 
elements  of  the  food  and  the  oxygen  of  the 
air  mutually  exercises  on  each  other.  The 
only  known  ultimate  cause  of  vital  force, 
either  in  animals  or  in  plants,  is  a  chemical 
process.  If  this  be  prevented,  the  pheno- 
mena of  life  do  not  manifest  themselves,  or 
they  cease  to  be  recognisable  by  our  senses. 
If  the  chemical  action  be  impeded,  the  vital 
phenomena  must  take  new  forms. 

According  to  the  experiments  of  Despretz, 
1  oz.  of  carbon  evolves,  during  its  combus- 
tion, as  much  heat  as  would  raise  the  tem- 
perature of  105  oz.  of  water  at  32°  to  167°, 
that  is,  by  135  degrees;  in  all,  therefore, 
105  times  135°=14207  degrees  of  heat. 
Consequently,  the  13*9  oz.  of  carbon  which 
are  daily  converted  into  carbonic  acid  in  the 
body  of  an  adult,  evolve  13-9xl4207°=» 
197477-3  degrees  of  heat.  This  amount  of 
heat  is  sufficient  to  raise  the  temperature  ol 
1  oz.  of  water  by  that  number  of  degrees, 
or  from  32°  to  197509-3°;  or  to  cause 
136-81bs.  of  water  at  32°  to  boil;  or  to 
heat  370  Ibs.  of  water  to  98-3°  (the  tem- 
perature of  the  human  body;)  or  to  convert 
into  vapour  24  Ibs.  of  water  at  98-3°. 

If  we  now  assume  that  the  quantity  ot 
water  vaporized  through  the  skin  and  lungs 
in  24  hours  amounts  to  48  oz.  (3  Ibs.,)  then 
there  will  remain,  after  deducting  the  neces- 
sary amount  of  heafr,  146380-4  degrees  of 
heat,  which  are  dissipated  by  radiation,  by 
heating  the  expired  air,  and  in  the  excre 
mentitious  matters. 

In  this  calculation,  no  account  has  been 
taken  of  the  heat  evolved  by  the  hydrogen 
of  the  food,  during  its  conversion  into  water 
by  oxidation  within  the  body.  But  if  Ave 
consider  that  the  specific  heat  of  the  bones, 
of  fat,  and  of  the  organs  generally,  is  far 
less  than  that  of  water,  and  that  conse- 
quently they  require,  in  order  to  be  heated 
to  98-3°,  much  less  heat  than  an  equal 
weight  of  water,  no  doubt  can  be  enter- 
tained, that  when  all  the  concomitant  cir- 
cumstances are  included  in  the  calculation, 
the  heat  evolved  in  the  process  of  combus- 
tion, to  which  the  food  is  subjected  in  the 
body,  is  amply  sufficient  to  explain  the  con- 
stant temperature  of  the  body,  as  well  as 
the  evaporation  from  the  skin  and  lungs. 

VI.  All  experiments  hitherto  made  on  the 
quantity  of  oxygen  which  an  animal  con 
sumes  in  a  given  time,  and  also  the  enn^l  i 


ANIMAL   CHEMISTRY. 


sions  deduced  from  them  as  the  origin  of 
animal  heat,  are  destitute  of  practical  value 
in  regard  to  this  question,  since  we  have 
seen  that  the  quantity  of  oxygen  consumed 
varies  according  to  the  temperature  and 
density  of  the  air,  according  to  the  degree 
of  motion,  labour,  or  exercise,  to  the  amount 
and  quality  of  food,  to  the  comparative 
warmth  of  the  clothing,  and  also  according 
to  the  time  within  which  the  food  is  taken. 
Prisoners  in  the  Bridewell  at  Marienschloss 
(a  prison  where  labour  is  enforced,)  do  not 
consume  more  than  10'5  oz.  of  carbon  daily ; 
those  in  the  House  of  Arrest  at  Giessen, 
who  are  deprived  of  all  exercise,  consume 
only  8*5  oz. ;  (6)  and  in  a  family  well  known 
to  me,  consisting  of  nine  individuals,  five 
adults,  and  four  children  of  different  ages, 
the  average  daily  consumption  of  carbon  for 
each,  is  not  more  than  9-£>  oz.  of  carbon.* 
We  may  safely  assume,  as  an  approxima- 
tion, that  the  quantities  of  oxygen  consumed 
in  these  diflerent  cases  are  in  the  ratio  of 
these  numbers  j  but  where  the  food  contains 
meat,  fat,  and  wine,  the  proportions  are 
altered  by  reason  of  the  hydrogen  in  these 
kinds  of  food  which  is  oxidised,  and  which, 
in  being  converted  into  water,  evolves  much 
more  heat  for  equal  weights. 

The  attempts  to  ascertain  the  amount  of 
heat  evolved  in  an  animal  for  a  given  con- 
sumption of  oxygen  have  been  equally 
unsatisfactory.  Animals  have  been  allowed 
to  respire  in  close  chambers  surrounded 
with  cold  water;  the  increase  of  tempera- 
ture in  the  water  has  been  measured  by  the 
thermometer,  and  the  quantity  of  oxygen 
consumed  has  been  calculated  from  the 
analysis  of  the  air  before  and  after  the  ex- 
periment. In  experiments  thus  conducted, 
it  has  been  found  that  the  animal  lost  about 
fa  more  heat  than  corresponded  to  the 
oxygen  consumed;  and  had  the  windpipe 
of  the  animal  been  tied,  the  strange  result 
would  have  been  obtained  of  a  rise  in  the 
temperature  of  the  water  without  any  con- 
sumption of  oxygen.  The  animal  was  at  the 
temperature  of  98°  or  99°,  and  the  water, 
in  the  experiments  of  Despretz,  was  at 
47'5°.  Such  experiments  consequently 
prove,  that  when  a  great  difference  exists 
between  the  temperature  of  the  animal  body 
and  that  of  the  surrounding  medium,  and 
when  no  motion  is  allowed,  more  heat  is 
given  off  than  corresponds  to  the  oxygen 
consumed,  In  equal  times,  with  free  and 
unimpeded  motion,  a  much  larger  quantity 
of  oxygen  would  be  consumed  without  a 
perceptible  increase  ir  .he  amount  of  heat 
lost.  The  cause  of  these  phenomena  is 


*  In  this  family,  the  monthly  consumption  was 
151  Ihs.  of  brown  bread,  70  Ibs.  white  bread,  132 
Ibs.  meat,  19  Ibs.  sugar,  15'9  Ibs.  butter,  57  maass 
(about  24  gallons)  ot  milk ;  the  carbon  of  the  po- 
tatoes and  other  vegetables,  of  the  poultry,  game, 
and  wine  consumed,  having  been  reckoned  as 
equal  to  that  contained  in  "the  excrementitious 
matters,  the  carbon  of  the  above  articles  wascon- 
siderf  d  as  Seing  converted  into  carbonic  acid. 


obvious.  They  appear  naturally  both  m 
man  and  animals  at  certain  seasons  of  the 
year,  and  we  say  in  such  cases  that  we  are 
freezing,  or  experience  the  sensation  of  cold. 
It  is  plain,  that  if  we  were  to  clothe  a  man 
in  a  metallic  dress,  and  tie  up  his  hands  and 
feet,  the  loss  of  heat,  for  the  sume  consump- 
tion of  oxygen,  would  be  far  greater  than 
if  we  were  to  wrap  him  up  in  fur  and 
woollen  cloth.  Nay,  in  the  latter  case,  we 
should  see  him  begin  to  perspire,  and  warm 
water  would  exude,  in  drops,  through  the 
finest  pores  of  his  skin. 

If  to  these  considerations  we  add,  that  de- 
cisive experiments  are  on  record,  in  which 
animals  were  made  to  respire  in  an  unna- 
tural position,  as  for  example,  lying  on  the 
back,  with  the  limbs  tied  so  as  to  preclude 
motion,  and  that  the  temperature  of  their 
bodies  was  found  to  sink  in  a  degree  appre- 
ciable by  the  thermometer,  we  can  hardly 
be  at  a  loss  what  value  we  ought  to  attach 
to  the  conclusions  drawn  from  such  experi- 
ments as  those  above  described. 

These  experiments  and  the  conclusions 
deduced  from  them,  in  short,  are  incapable 
of  furnishing  the  smallest  support  to  the 
opinion  that  there  exists,  in  the  animal  body, 
any  other  unknown  source  of  heat,  besides 
the  mutual  chemical  action  between  the  ele- 
ments of  the  food  and  the  oxygen  of  the  air. 
The  existence  of  the  latter  cannot  be  doubtpd 
or  denied,  and  it  is  amply  sufficient  to  ex- 
plain all  the  phenomena. 

VII.  If  we  designate  the  production  o( 
force,  the  phenomena  of  motion  in  the  ani- 
mal body  as  nervous  life,  and  the  resistance, 
the  condition  of  static  equilibrium,  as  vege- 
tative life  ;  it  is  obvious  that  in  all  classes 
of  animals  the  latter,  namely,  vegetative  life, 
prevails  over  the  former,  nervous  life,  in  the 
earlier  stages  of  existence. 

The  passage  or  change  of  matter  from  a 
state  of  motion  to  a  state  of  rest  appears  in 
an  increase  of  the  mass,  and  in  the  supply 
of  waste;  while  the  motion  itself,  or  the 
production  of  force,  appears  in  the  shape  of 
waste  of  matter. 

In  a  young  animal,  the  waste  is  less  than 
the  increase;  and  the  female  retains,  up  to 
a  certain  age,  this  peculiar  condition  of  a 
more  intense  vegetative  life.  This  condition 
does  not  cease  in  the  female  as  in  the  male, 
with  the  complete  development  of  all  the 
organs  of  the  body. 

The  female  in  the  lower  animals,  is,  ai 
certain  seasons,  capable  of  reproduction  of 
the  species.  The  vegetative  life  in  her  or- 
ganism is  rendered  more  intense  by  certain 
external  conditions,  such  as  temperature, 
food,&c. ;  the  organism  produces  more  than 
is  wasted,  and  the  result  is  the  capacity  of 
reproduction. 

In  the  human  species,  the  female  organism 
is  independent  of  those  external  causes 
which  increase  the  intensity  of  vegetative 
life.  When  the  organism  is  fully  developed, 
it  is  at  all  times  capable  of  reproduction  of 
the  »pecies ;  and  infinite  wisdom  has  given 


FIBRINE   AI\D   ALBUMEN. 


21 


.0  tn  J  femaie  body  the  power,  up  to  a  certain 
age,  cf  producing  all  parts  of  its  organization 
in  greater  quantity  than  is  required  to  sup- 
ply the  daily  waste. 

This  excess  of  production  can  be  shown 
to  contain  all  the  elements  of  a  new  organism, 
it  is  constantly  accumulating,  and  is  periodi- 
cally expelled  from  the  body,  until  it  is  ex- 
pended in  reproduction.  This  periodical 
discharge  ceases  when  the  ovum  has  been 
impregnated,  and  from  this  time  every  drop 
of  the  superabundant  blood  goes  to  produce 
an  organism  like  that  of  the  mother. 

Exercise  and  labour  cause  a  diminution 
in  the  quantity  of  the  menstrual  discharge; 
and  when  it  is  suppressed  in  consequence 
of  disease,  the  vegetative,  life  is  manifested 
in  a  morbid  production  of  fat.  When  the 
equilibrium  between  the  vegetative  and  ner- 
vous life  is  disturbed  in  the  male,  when,  as 
in  eunuchs,  the  intensity  of  the  latter  is  di- 
minished, the  predominance  of  the  former 
is  shown  in  the  same  form,  in  an  increased 
deposit  of  fat. 

VIII.  If  we  hold,  that  increase  of  mass  in 
he  animal  body,  the  development  of  its  or- 
gans, and  the  supply  of  waste, — that  ail  this 
is  dependent  on  the  blood,  that  is,  on  the 
ingredients  of  the  blood,  then  only  those 
substances  can  properly  be  called  nutritious, 
or  considered  as  food  which  are  capable  of 
conversion  into  blood.  To  determine,  there- 
fore, what  substances  are  capable  of  afford- 
ing nourishment,  it  is  only  necessary  to  as- 
certain the  composition  of  the  food,  and  to 
compare  it  with  that  of  the  ingredients  of 
the  blood. 

Two  substances  require  especial  conside- 
ration as  the  chief  ingredients  of  the  blood ; 
one  of  these  separates  immediately  from  the 
blood  when  withdrawn  from  the  circulation. 
It  is  well  known  that  in  this  case  blood 
coagulates,  and  separates  into  a  yellowish 
liquid,  the  serum  of  the  blood,  and  a  gela- 
tinous mass,  which  adheres  to  a  rod  or  stick 
in  soft,  elastic  fibres,  when  coagulating  blood 
is  briskly  stirred.  This  is  the^&rwe  of  the 
blood,  which  is  identical  in  all  its  properties 
with  muscular  fibre,  when  the  latter  is  pu- 
rified from  all  foreign  matters. 

The  second  principal  ingredient  of  the 
blood  is  contained  in  the  serum,  and  gives 
to  this  liquid  all  the  properties  of  the  white 
of  eggs,  with  which  it  is  identical.  When 
heated,  it  coagulates  into  a  white  elastic 
mass,  and  the  coagulating  substance  is 
called  albumen. 

Fibrine  and  albumen,  the  chief  ingredients 
of  blood,  contain,  in  all,  seven  chemical 
elements,  among  which  nitrogen,  phos- 
phrus,  and  sulphur  are  found.  They  con- 
tain also  the  earth  of  bones.  The  serum 
retains  in  solution  sea  salt  and  other  salts 
of  potash  and  soda,  in  which  the  acids  are 
carbonic,  phosphoric,  and  sulphuric  acids. 
The  globules  of  the  blood  contain  fibrine  and 
albumen,  along  with  a  red  colouring  matter, 
in  which  iron  is  a  constant  element.  Be- 
side these,  the  blood  contains  certain  fattv 


bodies  in  small  quantity,  which  differ  from 
ordinary  fats  in  several  of  their  properties. 

Chemical  analysis  has  led  to  the  remark- 
able result,  that  fibrine  and  albumen  contain 
the  same  organic  elements  united  in  the 
same  proportion,  so  that  two  analyses,  the 
one  of  fibrine  and  the  other  of  albumen,  do 
not  differ  more  than  two  analyses  of  fibrine 
or  two  of  albumen  respectively  do,  in  the 
composition  of  100  parts. 

In  these  two  ingredients  of  blood  the  par- 
ticles are  arranged  in  a  different  order,  as  is 
shown  by  the  difference  of  their  external 
properties ;  but  in  chemical  composition,  in 
the  ultimate  proportion  of  the  organic  ele- 
ments, they  are  identical. 

This  conclusion  has  lately  been  beautifully 
confirmed  by  a  distingufshed  physiologist 
(Denis,)  who  has  succeeded  in  converting 
fibrine  into  albumen,  that  is,  in  giving  it  the 
solubility,  and  coagulability  by  heat,  which 
characterize  the  white  of  egg. 

Pibrine  and  albumen,  besides  having  the 
same  composition,  agree  also  in  this,  that 
both  dissolve  in  concentrated  muriatic  acid, 
yielding  a  solution  of  an  intense  purple 
colour.  This  solution,  whether  made  with 
fibrine  or  albumen,  has  the  very  same  re- 
actions with  all  substances  yet  tried. 

Both  albumen  and  fibrine,  in  the  process 
of  nutrition,  are  capable  of  being  converted 
into  muscular  fibre,  and  muscular  fibre  is 
capable  of  being  reconverted  into  blood. 
These  facts  have  long  been  established  by 
physiologists,  and  chemistry  has  merely 
proved  that  these  metamorphoses  can  be 
accomplished  under  the  influence  of  a  cer- 
tain force,  without  the  aid  of  a  third  sub- 
stance, or  of  its  elements,  and  without  the 
addition  of  any  foreign  element,  or  the  sepa- 
ration of  any  element  previously  present  in 
these  substances. 

If  we  now  compare  the  composition  of  all 
organized  parts  with  that  of  fibrine  and  albu- 
men, the  following  relations  present  them- 
selves : 

All  parts  of  the  animal  body  which  have 
a  decided  shape,  which  forms  parts  of  or 
gans,  contain  nitrogen.  No  part  of  an  organ 
which  possesses  motion  and  life  is  destitute 
of  nitrogen ;  all  of  them  contain  likewise 
carbon  and  the  elements  of  water,  the  latter, 
however,  in  no  case  in  the  proportion  to 
form  water. 

The  chief  ingredients  of  .the  blood  contain 
nearly  17  per  cent,  of  nitrogen,  and  no  part 
of  an  organ  contains  less  than  17  per  cent, 
of  nitrogen.  (7) 

The  most  convincing  experiments  and 
observations  have  proved  that  the  animal 
body  is  absolutely  incapable  of  producing 
an  elementary  body,  such  as  carbon  or  ni- 
trogen, out  of  substances  which  do  not  con- 
tain it;  and  it  obviously  follows,  that  all 
kinds  of  food  fit  for  the  production  either  of 
blood,  or  of  cellular  tissue,  membranes,  skin, 
hair,  muscular  fibre,  &c.,  must  contain  a 
certain  amount  of  nitrogen,  because  that 
element  is  essential  to  the  composition  of 


22 


ANIMAL   CHEMISTRY 


the  above  named  organs ;  because  the  or- 
gans cannot  create  it  from  the  other  elements 
presented  to  them;  and,  finally,  because  no 
nitrogen  is  absorbed  from  the  atmosphere  in 
the  vital  process. 

The  substance  of  the  brain  and  nerves 
contains  a  large  quantity  of  albumen,  and, 
in  addition  to  this,  two  peculiar  fatty  acids, 
distinguished  from  other  fats  by  containing 
phosphorus  (phosphoric  acid?)  One  of 
these  contains  nitrogen  (Fremy.) 

Finally,  water  and  common  fat  are  those 
ingredients  of  the  body  which  are  destitute 
of  nitrogen.  Both  are  amorphus  or  unor- 
ganized, and  only  so  far  take  part  in  the 
vital  process  as  that  their  presence  is  re- 
quired for  the  due  performance  of  the  vital 
functions.  The  inorganic  constituents  of 
the  body  are,  iron,  lime,  magnesia,  common 
salt,  and  the  alkalies. 

IX.  The  nutritive  process  m  the  carni- 
vora  is  seen  in  its  simplest  form.  This  class 
of  animals  lives  on  the  blood  and  flesh  of 
the  graminivora ;  but  this  blood  and  flesh 
is,  in  all  its  properties,  identical  with  their 
own.  Neither  chemical  nor  physiological 
differences  can  be  discovered. 

The  nutriment  of  carnivorous  animals  is 
•derived  originally  from  blood ;  in  their  sto- 
mach it  becomes  dissolved,  and  capable  of 
reaching  all  other  parts  of  the  body ;  in  its 
passage  it  is  again  converted  into  blood, 
and  from  this  blood  are  reproduced  all 
those  parts  of  their  organization  which  have 
undergone  change  or  metamorphosis. 

With  the  exception  of  hoofs,  hair,  fea- 
.hers,  and  the  earth  of  bones,  every  part  of 
the  food  of  carnivorous  animals  is  capable 
of  assimilation. 

In  a  chemical  sense,  therefore,  it  may  be 
said  that  a  carnivorous  animal,  in  support- 
ing the  vital  process,  consumes  itself.  That 
which  serves  for  its  nutrition  is  identical 
with  those  parts  of  its  organization  which 
are  to  be  renewed. 

The  process  of  nutrition  in  graminivorous 
animals  appear  at  first  sight  altogether  dif- 
ferent. Their  digestive  organs  are  less  sim- 
ple, and  their  food  consists  of  vegetables, 
the  great  mass  of  which  contains  but  little 
nitrogen. 

From  what  substances,  it  may  be  asked, 
is  the  blood  formed,  by  means  of  which  their 
organs  are  developed  ?  This  question  may 
be  answered  with  certainty. 

Chemical  researches  have  shown,  that  all 
such  parts  of  vegetables  as  can  afford  nutri- 
ment to  animals  contain  certain  constituents 
which  are  rich  in  nitrogen ;  and  the  most 
ordinary  experience  proves  that  animals  re- 
quire for  their  support  and  nutrition  less  of 
these  parts  of  plants  in  proportion  as  they 
abound  in  the  nitrogenized  constituents. 
Animals  cannot  be  fed  on  matters  destitute 
of  these  nitrogenized  constituents. 

These  important  products  of  vegetation 
are  especially  abundant  in  the  seeds  ol  the 
different  kinds  of  grain,  and  of  pease,  beans, 
and  lentils:  i»  the  roots  and  the  iuices  of 


what  are  commonly  mailed  vegetables.  They 
exist,  howevej,  in  all  plants,  without  excep- 
tion, and  in  every  part  of  plants  in  larger  or 
smaller  quantity. 

These  nitrogenizea  forms  of  nutriment  in 
the  vegetable  kingdom  may  be  reduced  tc 
three  substances,  which  are  easily  distin* 
guished  by  their  external  characters.  Two 
of  them  are  soluble  in  water,  the  third  is 
insoluble. 

When  the  newly  expressed  juices  of 
vegetables  are  allowed  to  stand,  a  separation 
takes  place  in  a  few  minutes.  A  gelatinous 
precipitate,  commonly  of  a  green  tinge,  is 
deposited,  and  this,  when  acted  on  by  liquids 
which  remove  the  colouring  matter,  leaves 
a  grayish  white  subtance,  well  known  to 
druggists  as  the  deposit  from  vegetable  juices. 
This  is  one  of  the  nitrogenized  compounds 
which  serves  for  the  nutrition  of  animals, 
and  has  been  named  vegetable  Jibrine.  The 
juice  of  grapes  is  especially  rich  in  this 
constituent,  but  it  is  most  abundant  in  the 
seeds  of  wheat,  and  of  the  cerealia.  It  may 
be  obtained  from  wheat  flour  by  a  mechani- 
cal operation,  and  in  a  state  of  tolerable 
purity ;  it  is  then  called  gluten,  but  the  glutin- 
ous property  belongs,  not  to  vegetable  fibrine, 
but  to  a  foreign  substance,  present  in  small 
quantity,  which  is  not  found  in  the  other 
cerealia. 

The  method  by  which  it  is  obtained  suffi- 
ciently proves  that  it  is  insoluble  in  water  j 
although  we  cannot  doubt  that  it  was  origi- 
nally dissolved  in  the  vegetable  juice,  from 
which  it  afterwards  separated,  exactly  as 
fibrine  does  from  blood. 

The  second  nitrogenized  compound  re- 
mains dissolved  in  the  juice  after  the  sepa- 
ration of  the  fibrine.  It  does  not  separate 
from  the  juice  at  the  ordinary  temperature, 
but  is  instantly  coagulated  when  the  liquid 
containing  it  is  heated  to  the  boiling  point. 

When  the  clarified  juice  of  nutritious 
vegetables,  such  as  cauliflower,  asparagus, 
mangel  wurzel,  or  turnips,  is  made  to  boil, 
a  coagulum  is  formed,  which  it  is  absolutely 
impossible  to  distinguish  from  the  substance 
which  separates  as  coagulum,  when  the 
serum  of  blood  or  the  white  of  an  e°:g, 
diluted  with  water,  are  heated  to  the  boiling 
point.  This  is  vegetable  albumen.  It  is 
found  in  the  greatest  abundance  in  certain 
seeds,  in  nuts,  almonds,  and  others,  in 
which  the  starch  of  the  grammese  is  re- 
placed by  oil. 

The  third  nitrogenized  constituent  of  the 
vegetable  food  of  animals  is  vegetable  caserne. 
It  is  chiefly  found  in  the  seeds  of  pease, 
beans,  lentils,,  and  similar  leguminous  seeds. 
Like  vegetable  albumen,  it  is  soluble  in 
water,  but  differs  from  it  in  this,  that  its 
solution  is  not  coagulated  by  heat.  When 
the  solution  is  heated  or  evaporated,  a  skin 
forms  on  its  surface,  and  the  addition  of  an 
acid  causes  a  coagulum,  just  as  in  animal 
milk. 

These  three  nitrogenized  compounds,  ve- 
getable fihrine.  albumen,  and  r.aseine,  are 


USES    OP    THE    STARCH,    SUGAR,    &c. 


23 


the  true  mlrogenized  constituents  of  the 
food  of  graminivorous  animals;  all  other 
nitrogenized  compounds,  occurring  in  plants, 
are  either  rejected  by  animals,  as  in  the  case 
of  the  characteristic  principles  of  poisonous 
and  medicinal  plants,  or  else  they  occur  in 
the  food  in  such  very  small  proportion,  that 
they  cannot  possibly  contribute  to  the  in- 
crease of  mass  in  the  animal  body. 

The  chemical  analysis  of  these  three  sub- 
stances has  led  to  the  very  interesting  result 
that  they  contain  the  same  organic  elements, 
united  in  the  same  proportion  by  weight ; 
and,  what  is  still  more  remarkable,  that  they 
are  identical  in  composition  with  the  chief 
constituents  of  blood,  animal  fibrine,  and 
albumen.  They  all  three  dissolve  in  con- 
centrated muriatic  acid  with  the  same  deep 
purple  colour,  and  even  in  their  physical 
characters,  animal  fibrine  and  albumen  are 
in  no  respect  different  from  vegetable  fibrine 
and  albumen.  It  is  especially  to  be  noticed, 
that  by  the  phrase,  identity  of  composition 
we  do  not  here  imply  mere  similarity,  but 
that  even  in  regard  to  the  presence  and 
relative  amount  of  sulphur,  phosphorus,  and 
phosphate  of  lime,  no  difference  can  be 
observed.  (8) 

How  beautifully  and  admirably  simple, 
with  the  aid  of  these  discoveries,  appears  the 
process  of  nutrition  in  animals,  the  forma- 
tion of  their  organs,  in  which  vitality  chiefly 
resides  !  Those  vegetable  principles,  which 
in  animals  are  used  to  form  blood,  contain 
Ahe  chief  constituents  of  blood,  fibrine  and 
albumen,  ready  formed,  as  far  as  regards 
their  composition.  All  plants,  besides,  con- 
tain a  certain  quantity  of  iron,  which  re- 
appears in  the  colouring  matter  of  the  blood. 
Vegetable  fibrine  and  animal  fibrine,  veget- 
able albumen  and  animal  albumen,  hardly 
differ  even  in  form ;  if  these  principles  be 
wanting  in  the  food,  the  nutrition  of  the 
animal  is  arrested  ;  and  when  they  are  pre- 
sent, the  graminivorous  animal  obtains  in 
its  food  the  very  same  principles  on  the  pre- 
sence of  which  the  nutrition  of  the  car- 
nivora  entirely  depends. 

Vegetables  produce  in  their  organism  the 
blood  of  all  animals,  for  the  carnivora,  in 
consuming  the  blood  and  flesh  of  the  grami- 
nivora,  consume,  strictly  speaking,  only  the 
vegetable  principles  which  have  served  for 
the  nutrition  of  the  latter.  Vegetable  fibrine 
and  albumen  take  the  same  form  in  the 
stomach  of  the  graminivorous  animal  as 
animal  fibrine  and  albumen  do  in  that  of  the 
carnivorous  animal. 

From  what  has  been  said,  it  follows  that 
the  development  of  the  animal  organism  and 
its  growth  are  dependent  on  the  reception 
of  certain  principles  identical  with  the  chief 
constituents  of  blood. 

In  this  sense  we  may  say  that  the  animal 
organism  gives  to  blood  only  its  form ;  that 
it  is  incapable  of  creating  blood  out  of  other 
substances  which  do  not  already  contain 
the  chief  constituents  of  that  fluid.  We 
cannot,  indeed,  maintain  tha^  the  anima1 


!  organism  has  no  power  to  form  other  com- 
pounds, for  we  know  that  it  is  capable  of 
producing  an  extensive  series  of  compounds, 
differing  in  composition  from  the  chief  con- 
stituents of  blood ;  but  these  last,  which  form 
the  starting  point  of  the  series,  it  cannot 
produce. 

The  animal  organism  is  a  higher  kind  of 
vegetable,  the  development  of  which  begins 
with  those  substances,  with  the  production 
of  which  the  life  of  an  ordinary  vegetable 
ends.  As  soon  as  the  latter  has  borne  seed, 
it  dies,  or  a  period  of  its  life  comes  to  a  ter- 
mination. 

In  that  endless  series  of  compounds,  which 
begins  with  carbonic  acid,  ammonia,  and 
water,  the  sources  of  the  nutrition  of  veget- 
ables, and  includes  the  most  complex  consti 
tuents  of  the  animal  brain,  there  is  no  blank, 
no  interruption.  The  first  substance  capable 
of  affording  nutriment  to  animals  is  the  last 
product  of  the  creative  energy  of  vegetables. 

The  substance  of  cellular  tissue  and  of 
membranes,  of  the  brain  and  nerves,  these 
the  vegetable  cannot  produce. 

The  seemingly  miraculous  in  the  produc- 
tive agency  of  vegetables  disappears  in  a 
great  degree,  when  we  reflect  that  the  pro- 
duction of  the  constituents  of  blood  cannot 
appear  more  surprising  than  the  occurrence 
of  the  fat  of  beef  and  mutton  in  cocoa  beans, 
of  human  fat  in  olive  oil,  of  the  principal 
ingredient  of  butter  in  palm  oil,  and  of  horse 
fat  and  train  oil  in  certain  only  seeds. 

X.  While  the  preceding  considerations 
leave  little  or  no  doubt  as  to  the  way  in  which 
the  increase  of  mass  in  an  animal,  that  is, 
its  growth,  is  carried  on,  there  is  yet  to  be 
resolved  a  most  important  question,  namely, 
that  of  the  function  performed  in  the  animal 
system  by  substances  containing  no  nitrogen, 
such  as  sugar,  starch,  gum,  pectine,  &c. 

The  most  extensive  class  of  animals,  the 
graminivora,  cannot  live  without  these  sub- 
stances ;  their  food  must  contain  a  certain 
amount  of  one  or  more  of  them,  and  if  these 
compounds  are  not  supplied,  death  quickly 
ensues. 

This  important  inquiry  extends  also  to  the 
constituents  of  the  food  of  carnivorous  ani- 
mals in  the  earliest  periods  of  life ;  for  this 
food  also  contains  substances  which  are  not 
necessary  for  their  support  in  the  adult  stale. 

The  nutrition  of  the  young  of  carnivora 
is  obviously  accomplished  by  means  similar 
to  those  by  which  the  graminivora  are  nou- 
rished ;  their  development  is  dependant  on 
the  supply  of  a  fluid,  which  the  body  of  the 
mother  secretes  in  the  shape  of  milk. 

Milk  contains  only  one  nitrogenized  con- 
stituent, known  under  the  name  of  caseine  ; 
besides  this,  its  chief  ingredients  are  butter, 
(fat),  and  sugar  of  milk. 

The  blood  of  the  young  animal,  its  mus- 
cular fibre,  cellular  tissue,  nervous  matter, 
and  bones,  must  have  derived  their  origin 
from  the  nitrogenized  constituent  of  milk, 
the  caseine ;  for  butler  and  sugar  of  milk 
contain  no  nitrogen. 


24 


ANIMAL  CHEMISTRY. 


Now,  the  analysis  of  caseine  has  led  to  the  i  stricter,  a  goat,  a  rabbit,  or  a  bird,  we  find 

tnat  the  hair,  hoofs,  horns,  feathers,  or  bones 
of  these  animals,  are  expelled  from  the  body 
apparently  unchanged.  They  have  retained 
their  natural  form  and  aspect,  but  have  be- 
come brittle,  because  of  all  their  component 
parts  they  have  lost  only  that  one  which 
was  capable  of  solution,  namely,  the  gela- 
tine. Faeces,  properly  so  called,  do  not 
occur  in  serpents  any  more  than  in  carnivo- 
rous birds. 

We  find,  moreover,  that  when  the  serpent 
has  regained  its  original  weight,  every  other 
part  of  its  prey,  the  flesh,  the  blood,  the 
brain,  and  nerves,  in  short,  every  thing  has 
disappeared. 

The  only  excrement,  strictly  speaking 
is  a  substance  expelled  by  the  urinary  pasr 


result,  which,  alter  the  details  given  in  me 
last  section,  can  hardly  excite  surprise,  that 
this  substance  also  is  identical  in  composi- 
tion with  the  chief  constituents  of  blood, 
fibrine  and  albumen.  Nay,  more,  a  com- 
parison of  its  properties  with  those  of  veget- 
able caseine  has  shown  that  these  two  sub- 
stances are  identical  in  all  their  properties; 
insomuch  that  certain  plants,  such  as  peas, 
beans,  and  lentils,  are  capable  of  producing 
the  same  substance  which  is  formed  from 
the  blood  of  the  mother,  and  employed  in 
yielding  the  blood  of  the  young  animal.  (9) 

The  young  animal,  therefore,  receives,  in 
the  form  of  caseine,  which  is  distinguished 
from  fibrine  and  albumen  by  its  great  solu- 
bility, and  by  not  coagulating  when  heated, 
the  chief  constituent  of  the  mother's  blood. 
To  convert  caseine  into  blood  no  foreign 
substance  is  required,  and  in  the  conversion 
of  the  mother's  blood  into  caseine,  no  ele- 
ments of  the  constituents  of  the  blood  have 
been  separated.  When  chemically  ex- 
amined, caseine  is  found  to  contain  a  much 
larger  proportion  of  the  earth  of  bones  than 
blood  does,  and  that  in  a  very  soluble  form, 
capable  of  reaching  every  part  of  the  body. 
Thus,  even  in  the  earliest  period  of  its  life, 
the  development  of  the  organs,  in  which  vi- 
tality resides,  is,  in  the  carnivorous  animal, 
dependant  on  the  supply  of  a  substance, 
identical  in  organic  composition  with  the 
chief  constituents  of  its  blood. 

What,  then,  is  the  use  of  the  butter  and 
the  sugar  of  milk?  How  does  it  happen 
that  these  substances  are  indispensable  to 
life? 

Butter  and  sugar  of  milk  contain  no  fixed 
bases,  no  soda  or  potash.  Sugar  of  milk  has 
a  composition  closely  allied  to  that  of  the 
other  kinds  of  sugar,  of  starch,  and  of  gum; 
all  of  them  contain  carbon  and  the  elements 
of  water,  the  latter  precisely  in  the  propor- 
tion to  form  water. 

There  is  added,  therefore,  by  means  of 
these  compounds,  to  the  nitrogenized  con- 
stituents of  food,  a  certain  amount  of  carbon, 
or,  as  in  the  case  of  butter,  of  carbon  and 
hydrogen  ;  that  is,  an  excess  of  elements, 
which  cannot  possibly  be  employed  in  the 
production  of  blood,  because  the  nitrogenized 
substances  contained  in  the  food  already 
contain  exactly  the  amount  of  carbon  which 
is  required  for  the  production  of  fibrine  and 
albumen. 

The  following  considerations  will  show 
that  hardly  a  doubt  can  be  entertained,  that 
this  excess  of  carbon  alone,  or  of  carbon  and 
hydrogen,  is  expended  in  the  production  of 
animal  heat,  and  serves  to  protect  the  or- 
ganism from  the  action  of  the  atmospheric 
oxygen. 

XI.  In  order  to  obtain  a  clearer  insight 
into  the  nature  of  the  nutritive  process  in 
both  the  great  classes  of  animals,  let  us  first 
consider  the  changes  which  the  food  of  the 
carnivora  undergoes  in  their  organism. 

If  we  give  to  an  adult  serpent,  or  boa  con- 


When  dry,  it  is  pure  white,  like 
chalk;  it  contains  much  nitrogen,  and  a 
small  quantity  of  carbonate  and  phosphate 
of  lime  mixed  with  the  mass. 

This  excrement  is  urate  of  ammonia,  a 
chemical  compound,  in  which  the  nitrogen 
bears  to  the  carbon  the  same  proportion  as 
in  bicarbonate  of  ammonia.  For  every  equi- 
valent of  nitrogen  it  contains  two  equiva- 
lents of  carbon. 

But  muscular  fibre,  blood  membranes, 
and  skin,  contain  four  times  as  much  carbon 
for  the  same  amount  of  nitrogen,  or  eight 
equivalents  to  one  ;  and  if  we  add  to  this  the 
carbon  of  the  fat  and  nervous  substance,  it 
is  obvious  that  the  serpent  has  consumed 
for  every  equivalent  of  nitrogen,  much  more 
than  eight  equivalents  of  carbon. 

If  now  we  assume  that  the  urate  of  am- 
monia contains  all  the  nitrogen  of  the  animal 
consumed,  then  at  least  six  equivalents  of 
carbon,  which  were  in  combination  with  this 
nitrogen,  must  have  been  given  out  in  a  dif- 
ferent form  from  the  two  equivalents  which 
are  found  in  the  urate  of  ammonia. 

Now  we  know,  with  perfect  certainty, 
that  this  carbon  has  been  given  out  through 
the  skin  and  lungs,  which  could  only  take 
place  in  the  form  of  an  oxidized  product. 

The  excrements  of  a  buzzard  which  had 
been  fed  with  beef,  when  taken  out  of  the 
rectum,  consisted,  according  to  L.  Gmelin 
and  Tiedemann,  of  urate  of  ammonia.  In 
like  manner,  the  faeces  in  lions  and  tigers 
are  scanty  and  dry,  consisting  chietiy  of 
bone  earth,  with  mere  traces  of  compounds 
containing  carbon ;  but  their  urine  contains, 
not  urate  of  ammonia,  but  urea,  a  compound 
in  which  carbon  and  nitrogen  are  to  each 
other  in  the  same  ratio  as  in  neutral  carbon- 
ate of  ammonia. 

Assuming  that  their  food  (flesh,  &c.) 
contains  carbon  and  nitrogen  in  the  ratio  of 
eight  equivalents  to  one,  we  find  these  ele- 
ments in  their  urine  in  the  ratio  of  one  equi- 
valent to  one ;  a  smaller  proportion  of  car- 
bon, therefore,  than  in  serpents,  in  which 
respiration  is  so  much  less  active. 

The  whole  of  the  carbon  and  hydrogen 
which  the  food  of  these  animals  contained, 
beyond  the  amount  which  we  find  in  their 


FOOD    OF   t'ARNIVORA. 


25 


excrements.,  has  disappeared,  in  the  process 
of  respiration,  as  carbonic  acid  and  water. 

Had  the  animal  food  been  burned  in  a 
furnace,  the  change  produced  in  it  would 
only  have  differed  in  the  form  of  combina- 
tion assumed  by  the  nitrogen  from  that 
which  it  underwent  in  the  body  of  the  ani- 
mal. The  nitrogen  would  have  appeared, 
with  part  of  the  carbon  and  hydrogen,  as 
carbonate  of  ammonia,  while  the  rest  of  the 
carbon  and  hydrogen  would  have  formed 
carbonic  acid  and  water.  The  incombusti- 
ble parts  would  have  taken  the  form  of 
ashes,  and  any  part  of  the  carbon  uncon- 
sumed  from  a  deficiency  of  oxygen  would 
have  appeared  as  soot,  or  lamp-black.  Now 
the  solid  exciements  are  nothing  else  than 
the  incombustible,  or  imperfectly  burned, 
parts  of  the  food. 

In  the  preceding  pages  it  has  been  as- 
sumed that  the  elements  of  the  food  are  con- 
verted by  the  oxygen  absorbed  in  the  lungs 
into  oxidized  products;  the  carbon  into  car- 
bonic acid,  the  hydrogen  into  water,  and  the 
nitrogen  into  a  compound  containing  the 
same  elements  as  carbonate  of  ammonia. 

This  is  only  true  in  appearance;  the  body, 
no  doubt,  after  a  certain  time,  acquires  its 
original  weight.  The  amount  of  carbon, 
and  of  the  other  elements,  is  not  found  to  be 
increased — exactly  as  much  carbon,  hydro- 
gen, and  nitrogen  has  been  given  out  as  was 
supplied  in  the  food ;  but  nothing  is  more 
certain  than  that  the  carbon,  hydrogen,  and 
nitrogen  given  out,  although  equal  in 
amount  to  what  is  supplied  in  that  form,  do 
not  directly  proceed  from  the  food. 

It  would  be  utterly  irrationable  to  suppose 
that  the  necessity  of  taking  food,  or  the 
satisfying  the  appetite,  had  no  other  object 
than  the  production  of  urea,  uric  acid,  car- 
bonic acid,  and  other  excrementitious  mat- 
ters— of  substances  which  the  system  expels, 
and  consequently  applies  to  no  useful  pur- 
pose in  the  economy. 

In  the  adult  animal,  the  food  serves  to  re- 
store the  waste  of  matter;  certain  parts  of 
its  organs  have  lost  the  state  of  vitality, 
have  been  expelled  from  the  substance  of 
the  organs,  and  have  been  metamorphosed 
into  new  combinations,  which  are  amor- 
phous and  unorganized. 

The  food  of  the  carnivora  is  at  once  con- 
verted into  blood ;  out  of  the  newly  formed 
blood  those  parts  of  organs  which  have  un- 
dergone metamorphoses  are  reproduced. 
The  carbon  and  nitrogen  of  the  food  thus 
become  constituent  parts  of  organs. 

Exactly  as  much  carbon  and  nitrogen  is 
supplied  to  the  organs  by  the  blood,  that  is, 
ultimately,  by  the  food,  as  they  have  lost  by 
the  transformations  attending  the  exercise 
ot  their  functions. 

What  then,  it  may  be  asked,  becomes  of 
the  new  compounds  produced  by  the  trans- 
formations of  the  organs,  of  the  muscles,  of 
the  membranes  and  cellular  tissue  of  the 
nerves  and  brain? 

These  new  compounds  cannot,  owing  to 


their  solubility,  remain  in  the  situation 
where  they  are  fovmed,  for  a  well  known 
force,  namely  the  circulation  of  the  blood, 
opposes  itself  to  this. 

By  the  expansion  of  the  heart,  an  organ 
in  which  two  systems  of  tubes  meet,  which 
are  ramified  in  a  most  minute  network  of 
vessels  through  all  parts  of  the  body,  there 
is  produced  a  vacuum,  the  immediate  effect 
of  which  is,  that  all  fluids  which  can  pene- 
trate into  these  vessels  are  urged  with  great 
force  towards  one  side  of  the  heart  by  the 
external  pressure  of  the  atmosphere.  This 
motion  is  powerfully  assisted  by  the  con- 
traction of  the  heart,  alternating  with  its  ex- 
pansion, and  caused  by  a  force  independent 
of  the  atmospheric  pressure. 

In  a  word,  the  heart  is  a  forcing  pump, 
which  sends  arterial  blood  into  all  parts  of 
the  body ;  and  also  a  suction  pump,  by 
means  of  which  all  fluids  of  whatever  kind, 
as  soon  as  they  enter  the  absorbent  vessels 
which  communicate  with  the  veins,  are 
drawn  towards  the  heart.  This  suction, 
arising  from  the  vacuum  caused  by  the  ex- 
pansion of  the  heart,  is  a  purely  mechanical 
act,  which  extends,  as  above  stated,  to  fluids 
of  every  kind,  to  saline  solutions,  poisons, 
&c.  It  is  obvious,  therefore,  that  by  the 
forcible  entrance  of  arterial  blood  into  the 
capillary  vessels,  the  fluids  contained  in 
these,  in  other  words,  the  soluble  compounds 
formed  by  the  transformations  of  organized 
parts,  must  be  comj.  ?lled  to  move  towards 
the  heart. 

These  compounds  cannot  be  employed 
for  the  reproduction  of  those  tissues  from 
which  they  are  derived.  They  pass  through 
the  absorbent  and  lymphatic  vessels  into  the 
veins,  where  their  accumulation  would 
speedily  put  a  stop  to  the  nutritive  process, 
were  it  not  that  this  accumulation  is  pre- 
vented by  two  contrivances  adapted  ex- 
pressly to  this  purpose,  and  which  may  be 
compared  to  filtering  machines. 

The  venous  blood,  before  reaching  the 
heart,  is  made  to  pass  through  the  liver;  the 
arterial  blood,  on  the  other  hand,  passes 
through  the  kidneys ;  and  these  organs  sepa 
rate  from  both  all  substances  incapable  ot 
contributing  to  nutrition. 

Those  new  compounds  which  contain  the 
nitrogen  of  the  transformed  organs  are  col- 
lected in  the  urinary  bladder,  and  being  ut- 
terly incapable  of  any  further  application  in 
the  system,  are  expelled  from  the  body. 

Those,  again,  which  contain  the  carbon 
of  the  transformed  tissues,  are  collected  in 
the  gall  bladder  in  the  form  of  a  compound 
of  soda,  the  bile,  which  is  miscible  with 
water  in  every  proportion,  and  which,  pass- 
ing into  the  duodenum,  mixes  with  the 
chyme.  All  those  parts  of  the  bile  which,, 
during  the  digestive  process,  do  not  lose 
their  solubility,  return  during  that  process 
into  the  circulation  in  a  state  of  extreme  di- 
vision. The  soda  of  the  bile,  and  those 
highly  carbonized  portions  which  are  not 
precipitated  by  a  weak  acid  (together  making 


ANIMAL   CHEMISTRY. 


TyVtns  of  the  solid  contents  of  the  bile,)  re- 
tain the  capacity  of  resorption  by  the  ab- 
sorbents of  the  small  and  large  intestines; 
nay,  this  capacity  has  been  directly  proved 
by  the  administration  of  enemata  containing 
bile,  the  whole  of  the  bile  disappearing  wit1 
the  injected  fluid  in  the  rectum. 

Thus  we  know  with  certainty,  that  the 
nitrogenized  compounds,  produced  by  the 
metamorphosis  of  organized  tissues,  after 
being  separated  from  the  arterial  blood  by 
means  of  the  kidneys,  are  expelled  from  the 
body  as  Utterly  incapable  of  further  altera- 
tion ;  while  the  compounds,  rich  in  carbon, 
derived  from  the  same  source,  return  into 
the  system  of  carnivorous  animals. 

The  food  of  the  carnivora  is  identical  with 
the  chief  constituents  of  their  bodies,  and 
hence  the  metamorphoses  which  their  or- 
gans undergo  must  be  the  same  as  those 
which,  under  the  influence  of  the  vital  force, 
take  place  in  the  matters  which  constitute 
their  food. 

The  flesh  and  blood  consumed  as  food 
yield  their  carbon  for  the  support  of  the  re- 
spiratory process,  while  its  nitrogen  appears 
as  uric  acid,  ammonia,  or  urea.  But  pre- 
viously to  these  final  changes,  the  dead  flesh 
and  blood  become  living  flesh  and  blood, 
and  it  is,  strictly  speaking,  the  carbon  of  the 
compounds  formed  in  the  metamorphoses 
of  living  tissues  that  serves  for  the  produc- 
tion of  animal  heat. 

The  food  of  the  carnivora  is  converted 
into  blood,  which  is  destined  for  the  repro- 
duction  of  organized  tissues ;  and  by  means 
of  the  circulation  a  current  of  oxygen  is 
conveyed  to  every  part  of  the  body.  The 
globules  of  the  blood,  which  ia  themselves 
can  be  shown  to  take  no  share  in  the  nutri- 
tive process,  serve  to  transport  the  oxygen, 
which  they  give  up  in  their  passage  through 
the  capillary  vessels.  Here  the  current  of 
oxygen  meets  with  the  compounds  pro- 
duced by  the  transformation  of  the  tissues, 
and  combines  with  their  carbon  to  form  car- 
bonic acid,  with  their  hydrogen  to  form 
water.  Every  portion  of  these  substances 
which  escapes  this  process  of  oxidation  is 
sent  back  into  the  circulation  in  the  form  of 
the  bile,  which  by  degrees  completely  dis- 
appears. 

In  the  carnivora  the  bile  contains  the  car- 
bon of  the  metamorphosed  tissues;  this 
carbon  disappears  in  the  animal  body,  and 
the  bile  likewise  disappears  in  the  vital  pro- 
cess. Its  carbon  and  hydrogen  are  given 
out  through  the  skin  and  lungs  as  carbonic 
•»cid  and  water ;  and  hence  it  is  obvious  that 
me  elements  of  the  bile  serve  for  respiration 
and  for  the  production  of  animal  heat. 
Every  part  of  the  food  of  carnivorous  ani- 
mals is  capable  of  forming  blood ;  their  ex- 
crements, excluding  the  urine,  contain  only 
inorganic  substances,  such  as  phosphate  of 
lime ;  and  the  small  quantity  of  organic  mat- 
ter which  is  found  mixed  with  these  is  de- 
rived from  excretions,  the  use  of  which  is 
to  promote  their  passage  through  the  intes- 


tines, such  as  mucus.  These  excrements 
contain  no  bile  and  no  soda  ;  for  water  ex- 
tracts from  them  no  trace  of  anv  substance 
resembling  bile,  and  yet  bile  is  very  soluble 
in  water,  and  mixes  with  it  in  every  pro- 
portion. 

Physiologists  can  entertain  no  doubt  as  to 
the  origin  of  the  constituent  parts  of  the 
urine  and  of  the  bile.  When,  from  the  de- 
privation of  food,  the  stomach  contracts 
itself  so  as  to  resemble'  a  portion  of  intes- 
tine, the  gall-bladder,  for  want  of  the  motion 
which  the  full  stomach  gives  to  it,  cannot 
pour  out  the  bile  it  contains ;  hence  in  ani- 
mals starved  to  death  we  find  the  gall-blad- 
der distended  and  full.  The  secretion  of 
bile  and  urine  goes  on  during  the  winter 
sleep  of  hybernating  animals;  and  we 
know  that  the  urine  of  dogs,  fed  for  three 
weeks  exclusively  on  pure  sugar,  contains 
as  much  of  the  most  highly  nitrogenize* 
constituent,  urea,  as  in  the  normal  condition 
(Marchaud.  Erdmaun's  Journal  fur  prak- 
tische  Chemie,  XIV.  p.  495.) 

Differences  in  the  quantity  of  urea  se- 
creted in  these  and  similar  experiments  are 
explained  by  the  condition  of  the  animal  in 
regard  to  the  amount  of  the  natural  motions 
permitted.  Every  motion  increases  the 
amount  of  organized  tissue  which  under- 
goes metamorphosis.  Thus  after  a  walk, 
the  secretion  of  urine  in  man  is  invariably 
increased. 

The  urine  of  the  mammalia,  of  birds,  and 
of  amphibia,  contains  uric  acid  or  urea ;  and 
the  excrements  of  the  mollusca,  and  of  in- 
sects, as  of  cantharides  and  of  the  butterfly 
of  the  silkworm,  contain  urate  of  ammonia. 
This  constant  occurrence  of  one  or  two  ni- 
trogenized compounds  in  the  excretions  of 
animals,  while  so  great  a  difference  exists  in 
their  food,  clearly  proves  that  these  com- 
pounds proceed  from  one  and  the  same 
source. 

As  little  doubt  can  be  entertained  in  re- 
gard to  the  function  of  the  bile  in  the  vital 
process.  When  we  consider,  that  the  ace- 
tate of  potash,  given  in  enema,  or  simply 
as  a  bath  for  the  feet,  renders  the  urine 
strongly  alkaline  (Rehberger  in  Tiedemann's 
Zeitschrift  fur  Physiologic,  ii.  149,)  and  that 
the  change  which  the  acetic  acid  here  under- 
goes cannot  be  conceived  without  the  addi- 
tion of  oxygen,  it  is  obvious,  that  the  soluble 
constituents  of  the  bile,  prone  to  change  ia 
a  high  degree  as  we  know  them  to  be,  and 
which,  as  already  stated,  cannot  be  employed 
in  the  production  of  blood,  must,  when  re- 
:urned  through  the  intestines  into  the  circu- 
.ation,  in  like  manner  yield  to  the  influence 
of  the  oxygen  which  they  meet.  The  bile 
s  a  compound  of  soda,  the  elements  of 
which,  with  the  exception  of  the  soda,  dis- 
appears in  the  body  of  a  carnivorous  animal. 

In  the  opinion  of  many  of  the  most  dis- 
tinguished physiologists,  the  bile  is  intended 
solely  to  be  excreted ;  and  nothing  is  more 
certain,  than  that  a  substance  containing  so 
small  a  proportion  of  nitrogen  cat 


USES   OF  URINE   AND   BILE. 


27 


have  no  share  in  the  process  of  nutrition 
or  reproduction  of  organized  tissue.  But, 
quantitative  physiology  must  at  once  and 
decidedly  reject  the  opinion,,  that  the  bile 
serves  no  purpose  in  the  economy,  and  is 
incapable  of  further  change. 

No  part  of  any  organized  structure  con- 
tains soda ;  only  in  the  serum  of  the  blood, 
in  the  fat  of  the  brain,  and  ia  the  bile,  do 
we  meet  with  that  alkali.  When  the  com- 
pounds of  soda  in  the  blood  are  converted 
into  muscular  fibre,  membrane,  or  cellular 
tissue,  the  soda  they  contain  must  enter  into 
new  combinations.  The  blood  which  is 
transformed  into  organized  tissue  gives  up 
its  soda  to  the  compounds  formed  by  the 
metamorphoses  of  the  previously  existing 
tissues.  In  the  bile  we  find  one  of  those 
compounds  of  soda. 

Were  the  bile  intended  merely  for  excre- 
tion, we  should  find  it,  more  or  less  altered, 
and  also  the  soda  it  contains,  in  the  solid 
excrements.  But,  with  the  exception  of 
common  salt,  and  of  sulphate  of  soda, 
which  occur  in  all  the  animal  fluids,  only 
mere  traces  of  soda  are  to  be  found  in  the 
faeces.  The  soda  of  the  bile,  therefore,  at 
all  events,  must  have  returned  from  the  in- 
testinal canal  into  the  organism,  and  the 
same  must  be  true  of  the  organic  matters 
which  were  in  combination  with  it. 

According  to  the  observations  of  physio- 
logists, a  man  secretes  daily  from  17  to  24 
oz.  of  bile ;  a  large  dog,  36  oz. ;  a  horse  37 
Ibs.  ( Burdach's  Physiologie,  v.  p.  260.)  But 
the  faeces  of  a  man  do  not  on  an  average 
weigh  more  than  5£  oz. ;  and  those  of  a  horse 
28^  Ibs.,  of  which  21  Ibs.  are  water,  and  1\ 
Ibs.  dry  faeces.  (Boussingault.)  The  latter 
yield  to  alcohol  only  ^Vth  part  of  their 
weight  of  soluble  matter. 

If  we  assume  the  bile  to  contain  90  per 
cent,  of  water,  a  horse  secretes  daily  592  oz. 
of  bile,  containing  59*2  oz.  of  solid  matter ; 
while  7£  Ibs.  or  120  oz.  of  dried  excrement 
yield  only  6  oz.  of  matter  soluble  in  alcohol, 
which  might  possibly  be  bile.  But  this 
matter  is  not  bile ;  when  the  alcohol  is  dissi- 
pated by  evaporation,  there  remains  a  soft, 
i  unctuous  mass,  altogether  insoluble  in  water, 
[and  which,  when  incinerated,  leaves  no  al- 
kaline ashes,  no  soda.  (10.) 

During  the  digestive  process,  therefore, 
the  soda  of  the  bile,  and,  along  with  it,  all 
the  soluble  parts  of  that  fluid,  are  returned 
into  the  circulation.  This  soda  re-appears 
in  ihe  newly-formed  blood,  and,  finally,  we 
find  it  in  the  urine  in  the  form  of  phosphate, 
carbonate,  and  hippurate  of  soda.  Berzelius 
found  in  1,000  parts  of  fresh  human  faeces 
only  nine  parts  of  substance  similar  to  bile ; 
5  ounces,  therefore,  would  contain  only  21 
grains  of  dried  bile,  equivalent  to  219  grains 
of  fresh  bile.  But  a  man  secretes  daily 
from  9,640  to  11,520  grains  of  fluid  bile, 
that  is,  from  45  to  56  times  as  much  as  can 
be  detected  in  the  matters  discharged  by  the 
intestinal  canal. 

Whatever  opinion  we  may  entertain  of 


I  the  accuracy  of  the  physiological  experi- 
ments, in  regard  to  the  quantity  of  bile  se- 
creted by  the  different  classes  of  animals; 
thus  much  is  certain,  that  even  the  maxi- 
mum of  supposed  secretion,  in  man  and  in 
the  horse,  does  not  contain  as  much  carbon 
as  is  given  out  in  respiration.  With  all  the 
fat  which  is  mixed  with  it,  or  enters  into  its 
composition,  dried  bile  does  not  contain 
more  than  69  per  cent,  of  carbon.  Conse- 
quently, if  a  horse  secretes  57  Ibs.  of  bile, 
this  quantity  will  contain  only  40  ounces  of 
carbon.  But  the  horse  expires  daily  nearly 
twice  as  much  in  the  form  of  carbonic  acid. 
A  precisely  similar  proportion  holds  good  in 
man. 

Along  with  the  matter  destined  for  the 
formation  or  reproduction  of  organs,  the  cir- 
culation conveys  oxygen  to  all  parts  of  the 
body.  Now,  into  whatever  combination  the 
oxygen  may  enter  in  the  blood,  it  must  be 
held  as  certain,  that  such  of  the  constituents 
of  blood  as  are  employed  for  reproduction, 
are  not  materially  altered  by  it.  In  muscular 
fibre  we  find  fibrine,  with  all  the  properties 
it  had  in  venous  blood ;  the  albumen  in  the 
blood  does  not  combine  with  oxygen.  The 
oxygen  may  possibly  serve  to  convert  into 
the  gaseous  state  some  unknown  constituent 
of  the  blood;  but  those  well-known  con- 
stituents, which  are  employed  in  reproduc- 
tion, cannot  be  destined  to  support  the  respi- 
ratory process ;  none  of  their  properties  can 
justify  such  an  opinion. 

Without  attempting  in  this  place  to  ex- 
haust the  whole  question  of  the  share  taken 
by  the  bile  in  the  vital  operations,  it  follows, 
as  has  been  observed,  from  the  simple  com- 
parison of  those  parts  of  the  food  of  the  car- 
nivora  which  are  capable  of  assimilation, 
with  the  ultimate  products  into  which  it  is 
converted,  that  all  the  carbon  of  the  food, 
except  that  portion  which  is  found  in  the 
urine,  is  given  out  as  carbonic  acid. 

But  this  carbon  was  ultimately  derived 
from  the  substance  of  the  metamorphosed 
tissues ;  and  this  being  admitted,  the  ques- 
tion of  the  necessity  of  substances  contain- 
ing much  carbon  and  no  nitrogen  in  the  food 
of  the  young  of  the  carnivora,  and  in  that 
of  the  graminivora,  is  resolved  in  a  strikingly 
simple  manner. 

XII.  It  cannot  be  disputed  that  in  an 
adult  carnivorous  animal,  which  neither 
gains  nor  loses  weight  perceptibly  from  day 
to  day,  its  nourishment,  the  waste  of  organ- 
ized tissue,  and  its  consumption  of  oxygen* 
stand  to  each  other  in  a  well-defined  and! 
fixed  relation. 

The  carbon  of  the  carbonic  acid  given  off, 
with  that  of  the  urine ;  the  nitrogen  of  the 
urine,  and  the  hydrogen  given  off  as  am- 
monia and  water;  these  elements,  taken 
together,  must  be  exactly  equal  in  weight  to 
the  carbon,  nitrogen,  and  hydrogen  of  the 
metamorphosed  tissues,  and  since  these  last 
are  exactly  replaced  by  the  food,  to  the  car- 
bon, nitrogen,  and  hydrogen  of  Uie  food. 
Were  this  not  the  case,  the  weight  of  the 


ANIMAL   CHEMISTRY. 


animal    could    not    possibly    remain    un- 
changed. 

But,  in  the  young  of  the  carnivora,  the 
weight  does  not  remain  unchanged ;  on  the 
contrary,  it  increases  from  day  to  day  by  an 
appreciable  quantity. 

This  fact  presupposes,  that  the  assimila- 
tive process  in  the  young  animal  is  more 
energetic,  more  intense,  than  the  process  of 
transformation  in  the  existing  tissues.  If 
both  processes  were  equally  active,  the 
weight  of  the  body  could  not  increase;  and 
were  the  waste  by  transformation  greater, 
the  weight  of  the  body  would  decrease. 

Now,  the  circulation  in  the  young  animal 
is  not  weaker,  but,  on  the  contrary,  more 
rapid ;  the  respirations  are  more  frequent ; 
and,  for  equal  bulks,  the  consumption  of 
oxygen  must  be  greater  rather  than  smaller 
in  the  young  than  in  the  adult  animal.  But, 
since  the  metamorphosis  of  organized  parts 
goes  on  more  slowly,  there  would  ensue  a 
deficiency  of  those  substances,  the  carbon 
and  hydrogen  of  which  are  adapted  for  com- 
bination with  oxygen ;  because,  in  the  car- 
nivora it  is  the  new  compounds,  produced 
by  the  metamorphosis  of  organized  parts, 
which  nature  has  destined  to  furnish  the  ne- 
cessary resistance  to  the  action  of  the  oxy- 
gen, and  to  produce  animal  heat.  What  is 
wanting  for  these  purposes  an  infinite  wis- 
dom has  supplied  to  the  young  animal  in  its 
natural  food. 

The  carbon  and  hydrogen  of  butter,  and 
the  carbon  of  the  sugar  of  milk,  no  part  of 
either  of  which  can  yield  blood,  fibrine,  or 
albumen,  are  destined  for  the  support  of  the 
respiratory  process,  at  an  age  when  a  greater 
resistance  is  opposed  to  the  metamorphosis 
of  existing  organisms;  or,  in  other  words, 
to  the  production  of  compounds,  which  in 
the  adult  state  are  produced  in  quantity 
amply  sufficient  for  the  purpose  of  respira- 
tion. 

The  young  animal  receives  the  constitu- 
ents of  its  blood  in  the  caseine  of  the  milk. 
A  metamorphosis  of  existing  organs  goes  on, 
for  bile  and  urine  are  secreted ;  the  matter 
of  the  metamorphosed  parts  is  given  off  in 
the  form  of  urine,  of  carbonic  acid,  and  of 
water;  but  the  butter  and  sugar  of  milk  also 
disappear;  they  cannot  be  detected  in  the 
faeces. 

The  butter  and  sugar  of  milk  are  given 
out  in  the  form  of  carbonic  acid  and  water, 
and  their  conversion  into  oxidized  products 
furnishes  the  clearest  proof  that  far  more 
oxygen  is  absorbed  than  is  required  to  con- 
vert the  carbon  and  hydrogen  of  the  meta- 
morphosed tissues  into  carbonic  acid  and 
water. 

The  change  and  metamorphosis  of  organ- 
ized tissues  going  on  in  the  vital  process  in 
the  young  animal,  consequently  yield,  in  a 
given  time,  much  less  carbon  and  hydrogen 
in  the  form  adapted  for  the  respiratory  pro- 
cess than  corresponds  to  the  oxygen  taken  up 
in  the  lungs.  The  substance  of  its  organized 
parts  would  undergo  a  more  rapid  consump- 


tion, and  would  necessarily  yield  to  the 
action  of  the  oxyge'n,  were  not  the  deficiency 
of  carbon  and  hydrogen  supplied  from 
another  source. 

The  continued  increase  of  mass,  or 
growth,  and  the  free  and  unimpeded  de- 
velopement  of  the  organs  of  the  young 
animal,  are  dependent  on  the  presence  of 
foreign  substances,  which,  in  the  nutritive 
process,  have  no  other  function  than  to  pro- 
tect the  newly-formed  organs  from  the  action 
of  the  oxygen.  It  is  the  elements  of  these 
substances  which  unite  with  the  oxygen ; 
the  organs  themselves  could  not  do  so  with- 
out being  consumed ;  that  is,  growth,  or 
increase  of  mass  in  the  body,  the  consump- 
tion of  oxygen  remaining  the  same,  would 
be  utterly  impossible. 

The  preceding  considerations  leave  no 
doubt  as  to  the  purpose  for  which  Nature 
has  added  to  the  food  of  the  young  of  car- 
nivorous mammalia  substances  devoid  of 
nitrogen,  which  their  organism  cannot  em- 
ploy for  nutrition,  strictly  so.  called,  that  is, 
for  the  production  of  blood ;  substances 
which  may  be  entirely  dispensed  with  in 
their  nourishment  in  the  adult  state.  In  the 
young  of  carnivorous  birds,  the  want  of  all 
motion  is  an  obvious  cause  of  diminished 
waste  in  the  organized  parts  ;  hence,  milk  is 
not  provided  for  them. 

The  nutritive  process  in  the  carnivora 
thus  presents  itself  in  two  distinct  forms; 
one  of  which  we  again  meet  with  in  the 
graminivora. 

XIII.  In  the  class  of  graminivorous  ani 
mals,  we  observe,  that  during  their  whole 
life,  their  existence  depends  on  the  supply 
of  substances  having  a  composition  identical 
with  that  of  sugar  of  milk,  or  closely  re- 
sembling it.  Every  thing  that  they  consume 
as  food  contains  a  certain  quantity  of  starch, 
or  gum,  or  sugar,  mixed  with  other  matters. 

The  most  abundant  and  widely-extended 
of  the  substances  of  this  class  is  amylon  or 
starch  ;  it  occurs  in  roots,  seeds,  and  stalks, 
and  even  in  wood,  deposited  in  the  form  oJ 
roundish  or  oval  globules,  which  differ  from 
each  other  in  size  alone,  being  identical  in 
chemical  composition.  (11.)  In  the  same 
plant,  in  the  pea,  for  example,  we  find 
starch,  the  globules  of  which  differ  in  size. 
Those  in  the  expressed  juice  of  the  stalks 
have  a  diameter  of  from  ^fo-  to  T£o  of  an 
inch,  while  those  in  the  seeds  are  three  or 
four  times  larger.  The  globules  in  arrow- 
root and  in  potato  starch  are  distinguished 
by  their  large  size ;  those  of  rice  and  of 
wheat  are  remarkably  small. 

It  is  well  known  that  starch  may  be  con- 
verted into  sugar  by  very  different  means. 
This  change  occurs  in  the  process  of  germi- 
nation, as  in  malting,  and  it  is  easily  accom- 
plished by  the  action  of  acids.  The  meta- 
morphosis of  starch  into  sugar  depends 
simply,  as  is  proved  by  analysis,  on  the  ad- 
dition of  the  elements  of  water.  (12.)  All 
the  carbon  of  the  starch  is  fo'ind  in  the 
sugar-  none  of  its  elements  have  been 


NUTRITION   OP   THE    GRAMINIVORA. 


29 


sepaiated,  and,  except  the  elements  of  water, 
no  foreign  element  has  been  added  to  it  in 
this  transformation. 

In  many,  especially  in  pulpy  fruits,  which 
when  unripe  are  sour  and  rough  to  the  taste, 
out  when  ripe  are  sweet,  as,  for  example, 
in  apples  and  pears,  the  sugar  is  produced 
from  the  starch  which  the  unripe  fruit  con- 
tains. 

If  we  rub  unripe  apples  or  pears  on  a 
grater  to  a  pulp,  and  wash  this  with  cold 
water  on  a  fine  sieve,  the  turpid  liquid  which 
passes  through  deposits  a  very  fine  Hour  of 
starch,  of  which  not  even  a  trace  can  be 
detected  in  the  ripe  fruit.  Many  varieties 
become  sweet  while  yet  on  the  tree  ;  these 
are  the  summer  or  early  apples  and  pears. 
Others,  again,  become  sweet  only  after  hav- 
ing been  kept  for  a  certain  period  after  gath- 
ering. The  after- ripening,  as  this  change  is 
called,  is  a  purely  chemical  process,  entirely 
independent  of  the  vitality  of  the  plant. 
When  vegetation  ceases,  the  fruit  is  capable 
of  reproducing  the  species,  that  is,  the  kernel, 
stone,  or  true  seed  is  fully  ripe,  but  the 
fleshy  covering  from  this  period  is  subjected 
to  the  action  of  the  atmosphere.  Like  all 
substances  in  a  state  of  eremacausis,  or 
decay,  it  absorbs  oxygen,  and  gives  off  a 
certain  quantity  of  carbonic  acid  gas. 

In  the  same  way  as  the  starch  in  putre- 
fying paste,  in  which  it  is  in  contact  with 
decaying  gluten,  is  converted  into  sugar, 
the  starch  in  the  above-named  fruits,  in  a 
state  of  decay,  or  eremacausis,  is  trans- 
formed into  grape  sugar.  The  more  starch 
the  unripe  fruit  contains,  the  sweeter  does 
it  become  when  ripe. 

A  close  connexion  thus  exists  between 
sugar  and  starch.  By  means  of  a  variety 
of  chemical  actions,  which  exert  no  other 
influence  on  the  elements  of  starch  than 
that  of  changing  the  direction  of  their  mu- 
tual attraction,  we  can  convert  starch  into 
sugar,  but  it  is  always  grape  sugar. 

Sugar  of  milk  in  many  respects  resembles 
starch ;  (13)  it  is,  by  itself,  incapable  of  the 
vinous  fermentation,  but  it  acquires  the  pro- 
perty of  resolving  itself  into  alcohol  and 
carbonic  acid  when  it  is  exposed  to  heat  in 
contact  with  a  substance  in  the  state  of  fer- 
mentation (such  as  putrefying  cheese  in 
milk.)  In  this  case,  it  is  first  converted  into 
grape  sugar ;  and  it  undergoes  the  same 
transformation,  when  it  is  kept  in  contact 
with  acids — with  sulphuric  acid,  for  exam- 
ple— at  the  ordinary  temperature. 

Gum  has  the  same  composition  in  100 
parts  as  cane  sugar.  (14.)  It  is  distinguished 
from  the  different  varieties  of  sugar  by  its 
not  possessing  the  property  of  being  resolved 
into  alcohol  and  carbonic  acid  by  the  pro- 
cess of  putrefaction.  When  placed  in  con- 
tact with  fermenting  substances,  it  under- 
goes no  appreciable  change,  whence  we 
may  conclude,  with  some  degree  of  proba- 
bility, that  its  elements,  in  the  peculiar  ar- 
rang^ment  according  to  which  they  are 
united,  are  held  together  with  a  stronger 


force  than  the  elements  of  Cut  different  kinds 
of  sugar. 

There  is,  however,  a  certain  relation  be- 
tween gum  and  sugar  of  milk,  since  both 
of  them,  when  treated  with  nitric  acid,  yield 
the  same  oxidized  product,  namely  niucic 
acid,  which  cannot,  under  the  same  circum- 
stances, be  formed  from  any  >f  :he  other 
kinds  of  sugar. 

In  order  to  show  more  distinctly  the  simi- 
larity of  composition  in  these  different  sub- 
stances, which  perform  so  important  a  part  in 
the  nutritive  process  of  the  graminivora,  let 
us  represent  one  equivalent  of  carbon  by  C 
(=75-8,)  and  one  equivalent  of  water  by 
aqua  (=112*4,)  we  shall  then  have  for  the 
composition  of  these  substances  the  follow- 
ing expressions : 

Starch      .     . 
Cane  sugar 
Gum        .     . 
Sugar  of  milk 
Grape  sugar 


=12C4- 10  aqua. 
=12  Of- 10  aqua-J-1  aqua, 
=12  C4-10  aqua-j-1  aqua 
=12  C+10  aqua+2  aqua. 
=12  C-}-10  aqua-j-4  aqua, 


For  the  same  number  of  equivalents  of 
carbon,  starch  contains  10  equivalents,  cane 
sugar  and  gum  1 1  equivalents,  sugar  of  milk 
12  equivalents,  and  grape-sugar  14  equiva- 
lents of  water,  or  the  elements  of  water. 

XIV.  In  these  different  substances,  some 
one  of  which  is  never  wanting  in  the  fcod 
of  the  graminivora,  there  is  added  to  the 
nitrogenized  constituents  of  this  food,  to  the 
vegetable  albumen,  fibrine,  and  caseine, 
from  which  their  blood  is  formed,  strictly 
speaking,  only  a  certain  excess  of  carbon, 
which  the  animal  organism  cannot  possibly 
employ  to  produce  fibrine  or  albumen,  be- 
cause the  nitrogenized  constituents  of  the 
food  already  contain  the  carbon  necessary 
for  the  production  of  blood,  and  because  the 
blood  in  the  body  of  the  carnivora  is  formed 
without  the  aid  of  this  excess  of  carbon. 

The  function  formed  in  the  vital  process 
of  the  graminivora  by  these  substances  (su- 
gar, gum,  &,c.)  is  indicated  in  a  very  clear 
and  convincing  manner,  when  we  take  into 
consideration  the  very  small  relative  amount 
of  the  carbom  which  these  animals  consume 
in  the  nitrogenized  constituents  of  their  food, 
which  bears  no  proportion  whatever  to  the 
oxygen  absorbed  through  the  skin  and  lungs. 

A  horse,  for  example,  can  be  kept  in  a 
perfectly  good  condition,  if  he  obtains  as 
food  15'lbs.  of  hay  and  4£  Ibs.  of  oats  daily. 
If  we  now  calculate  the  whole  amount  of 
nitrogen  in  these  matters,  as  ascertained  by 
analysis  (1-5  per  cent,  in  the  hay,  2*2  per 
cent,  in  the  oats,)  (15)  in  the  form  of  blood, 
that  is,  as  fibrine  and  albumen,  with  the  due 
proportion  of  water  in  blood,  (80  per  cent.,) 
the  horse  receives  daily  no  more  than  4£  oz. 
of  nitrogen,  corresponding  to  about  8  Ibs.  of 
blood.  But  along  with  this  nitrogen,  that 
is,  combined  with  it  in  the  form  of  fibrine  or 
albumen,  the  animal  receives  only  about  14£ 
oz.  of  carbon.  Only  about  8  oz.  of  this  can 
be  employed  to  support  respiration,  for  with 
the  nitrogen  expelled  in  the  urine  there  are 
C* 


30 


ANIMAL    CHEMISTRY. 


combined,  in  the  form  of  urea,  3  oz.,  and  in 
the  form  of  hippuric  acid,  3£  oz.  of  carbon. 
Without  going  further  into  the  calculation 
it  will  readily  be  admitted,  that  the  volume 
of  air  inspired  and  expired  by  a  horse,  the 
quantity  of  oxygen  consumed,  and,  as  a 
necessary  consequence,  the  amount  of  car- 
bonic acid  given  out  by  the  animal,  is  much 
greater  than  in  the  respiratory  process  in 
man.  But  an  adult  man  consumes  daily 
about  14  oz.  of  carbon,  and  the  determination 
of  Boussingault,  according  to  which  a 
horse  expires  79  oz.  daily,  cannot  be  very  far 


from  the  truth. 

In   the  nitrogen  ized 


constituents   of  his 


food,  therr/bre,  the  horse  receives  rather  less 
than  the  fifth  part  of  the  carbon  which  his 
organism  requires  for  the  support  of  the  re- 
spiratory process  ;  and  we  see  that  the  wis- 
dom of  the  Creator  has.  added  to  his  food 
the  £ths  which  are  wanting,  in  various 
forms,  as,  starch,  sugar,  &c.  with  which  the 
animal  must  be  supplied,  or  his  organism 
will  be  destroyed  by  the  action  of  the  oxygen. 

It  is  obvious,  that  in  the  system  of  the  gra- 
minivora,  whose  food  contains  so  small  a 
proportion,  relatively,  of  the  constituents  of 
blood,  the  process  of  metamorphosis  in  ex- 
isting tissues,  and  consequently  their  resto- 
ration or  reproduction,  must  go  on  far  less 
rapidly  than  in  the  carnivora.  Were  this 
not  the  case,  a  vegetation  a  thousand  times 
more  luxuriant  than  the  actual  one  would 
not  suffice  for  their  nourishment.  Sugar, 
gum,  and  starch  would  no  longer  be  neces- 
sary to  support  life  in  these  animals,  be- 
cause, in  that  case,  the  products  of  the 
waste,  or  metamorphosis  of  the  organized 
tissues,  would  contain  enough  of  carbon  to 
support  the  respiratory  process. 

Man,  when  confined  to  animal  food,  re- 
quires for  his  support  and  nourishment  ex- 
tensive sources  of  food,  even  more  widely 
extended  than  the  lion  and  tiger,  because, 
when  he  has  the  opportunity,  he  kills  with- 
out eating. 

A  nation  of  hunters,  on  a  limited  space, 
is  utterly  incapable  of  increasing  its  num- 
bers beyond  a  certain  point,  which  is  soon 
attained.  The  carbon  necessary  for  respira- 
tion must  be  obtained  from  the  animals,  of 
which  only  a  limited  number  can  live  on  the 
space  supposed.  These  animals  collect  from 
the  plants  the  constituents  of  their  organs 
and  of  their  blood,  and  yield  them,  in  turn, 
to  the  savages  who  live  by  the  chase  alone. 
They,  again,  receive  this  food  unaccompa- 
nied by  those  compounds,  destitute  of  nitro- 
gen, which,  during  the  life  of  the  animals, 
served  to  support  the  respiratory  process. 
In  such  men,  confined  to  an  animal  diet,  it 
is  the  carbon  of  the  flesh  and  of  the  blood 
which  must  take  the  place  of  starch  and 
sugar. 

But  151bs.  of  flesh  contain  not  more  car- 
bon than  4  Ibs.  of  starch,  (16)  and  while  the 
savage  with  one  animal  and  an  equal  weight 
of  starch  could  maintain  life  and  health  for 
a  certain  number  of  days,  he  would  be  com- 


pelled, if  confined  to  flesh/in  order  to  pro- 
cure the  carbon  necessary  for  respiration, 
during  the  same  time,  to  consume  five  such 
animals. 

It  is  easy  to  see,  from  these  considerations, 
how  close  the  connexion  is  between  agricul- 
ture and  the  multiplication  of  the  human 
species.  The  cultivation  of  our  crops  has 
ultimately  no  other  object  than  the  produc- 
tion of  a  maximum  of  those  substances 
which  are  adapted  for  assimilation  and  re- 
spiration, in  the  smallest  possible  space. 
Grain  and  other  nutritious  vegetables  yield 
us,  not  only  in  starch,  sugar,  and  gum,  the 
carbon  which  protects  our  organs  from  the 
action  of  oxygen,  and  produces  in  the  or- 
ganism the  heat  which  is  essential  to  life, 
but  also  in  the  form  of  vegetable  fibrine,  al- 
bumen, and  caseine,  our  blood,  from  which 
the  other  parts  of  our  body  are  developed 

Man,  when  confined  to  animal  food,  re- 
spires, like  the  camivora,  at  the  expense  of 
the  matters  produced  by  the  metamorphosis 
of  organized  tissues ;  and,  just  as  the  lion, 
tiger,  hyaena,  in  the  cages  of  a  menagerie, 
are  compelled  to  accelerate  the  waste  of  the 
organized  tissues  by  incessant  motion,  in  or- 
der to  furnish  the  matter  necessary  for  re- 
spiration, so  the  savage,  for  the  very  same 
object,  is  forced  to  make  the  most  laborious 
exertions  and  go  through  a  vast  amount  of 
muscular  exercise.  He  is  compelled  to  con- 
sume force  merely  in  order  to  supply  mat- 
ter for  respiration. 

Cultivation  is  the  economy  of  force.  Sci- 
ence teaches  us  the  simplest  means  of  ob- 
taining the  greatest  effect  with  the  smallest 
expenditure  of  power,  and  with  given 
means  to  produce  a  maximum  of  force.  The 
unprofitable  exertion,  of  power,  the  waste  of 
force  in  agriculture,  in  other  branches  of  in- 
dustry, in  science,  or  in  social  economy,  is 
characteristic  of  the  savage  state,  or  of  the 
want  of  cultivation. 

XV.  A  comparison  of  the  urine  of  the 
carnivora  with  that  of  the  graminivora 
shows  very  clearly,  that  the  process  of  meta- 
morphosis in  the  tissues  is  different,  both  in 
form  and  in  rapidity,  in  the  two  classes  of 
animals. 

The  urine  of  carnivorous  animals  is  acid, 
and  contains  alkaline  bases  united  with  uric, 
Dhosphoric,  and  sulphuric  acids.  We  know 
3erfectly  the  source  of  the  two  latter  acids. 
All  the  tissues,  with  the  exception  of  cellular 
tissue  and  membrane,  contain  phosphoric 
cid  and  sulphur,  which  latter  element  is 
converted  into  sulphuric  acid  by  the  oxygen 
f  the  arterial  blood.  In  the  various  fluids 
f  the  body  there  are  only  traces  of  phos- 
)hates  or  sulphates,  except  in  the  urine, 
where  both  are  found  in  abundance.  It  is 
?lain  that  they  are  derived  from  the  meta- 
morphosed tissues;  they  enter  into  the  ve- 
ious  blood  in  the  form  of  soluble  salts,  and 
ire  separated  from  it  in  its  passage  through 
he  kidneys. 

The  urine  of  the  graminivora  is  alkaline; 
t  contains  alkaline  carbonates  in  abundance, 


ORIGIN   OF   FAT   IN   ANIMALS. 


31 


and  so  small  a  portion  of  alkaline  phos- 
phates as  to  have  been  overlooked  by  most 
observers. 

The  deficiency  or  absence  of  alkaline 
phosphates  in  the  urine  of  the  graminivora, 
obviously  indicates  the  slowness  with  which 
the  tissues  in  this  class  of  animals  are  meta- 
morphosed ;  for  if  we  assume  that  a  horse 
consumes  a  quantity  of  vegetable  fibrine 
and  albumen  corresponding  to  the  amount  of 
nitrogen  in  his  daily  food  (about  4$  oz.,)  and 
that  the  quantity  of  tissue  metamorphosed 
is  equal  to  that  newly  formed,  then  the 
quantity  of  phosphoric  acid  which  on  these 
suppositions  would  exist  in  the  urine  is  not 
so  small  as  not  to  be  easily  detected  by  analy- 
sis in  the  daily  secretion  of  urine  (3  Ibs. 
according  to  Boussingault ;)  for  it  would 
amount  to  0.8  per  cent.  But,  as  above 
stated,  most  observers  have  been  unable  to 
detect  phosphoric  acid  in  the  urine  of  the 
horse. 

Hence  it  is  obvious  that  the  phosphoric 
acid  which  in  consequence  of  the  metamor- 
phosis of  tissues  is  produced  in  the  form  of 
soluble  alkaline  phosphates,  must  re-enter 
the  circulation  in  this  class  of  animals.  It 
is  there  employed  in  forming  brain  and  ner- 
vous matter,  to  which  it  is  essential,  and 
also,  no  doubt,  in  contributing  to  the  supply 
of  the  earthy  part  of  the  bones.  It  is  pro- 
bable, however,  that  the  greater  part  of  the 
earth  of  bones  is  obtained  by  the  direct  as- 
similation of  phosphate  of  lime,  while  the 
soluble  phosphates  are  better  adapted  for  the 
production  of  nervous  matter. 

In  the  graminivora,  therefore,  whose  food 
contains  so  small  a  proportion  of  phos- 
phorus or  of  phosphates,  the  organism  col- 
lects all  the  soluble  phosphates  produced  by 
the  metamorphosis  of  tissues,  and  employs 
them  for  the  developement  of  the  bones  and 
of  the  phosphorised  constituents  of  the 
brain  ;  the  organs  of  excretion  do  not  sepa- 
rate these  salts  from  the  blood.  The  phos- 
phoric acid,  which,  by  the  change  of  matter, 
is  separated  in  the  uncombined  state,  is  not 
expelled  from  the  hody  as  phosphate  of  soda ; 
but  we  find  it  in  the  solid  excrements  in  the 
form  of  insoluble  earthy  phosphates. 

XVI.  If  we  now  compare  the  capacity 
for  increase  of  mass,  the  assimilative  power 
in  the  graminivora  and  carnivora,  the  com- 
monest observations  indicate  a  very  marked 
difference. 

A  spider,  which  sucks  with  extreme  vo- 
racity the  blood  of  the  first  fly,  is  not  dis- 
turbed or  excited  by  a  second  or  third.  A 
cat  will  eat  the  first,  and  perhaps  the  second 
motive  presented  to  her,  but  even  if  she  kills 
a  third,  she  does  not  devour  it.  Exactly 
similar  observations  have  been  made  in  re- 
gard to  lions  and  tigers,  which  only  devour 
their  prey  when  urg^d  by  hunger.  Carni- 
vorous animals,  indeed,  require  less  food  for 
their  mere  support,  because  their  skin  is 
destitute  of  perspiratory  pores,  and  because 
they  consequently  lose,  for  equal  bulks, 
much  less  heat  than  2r,iiuinivorous  ani- 


mals, which  are  compelled  to  restore  the 
lost  heat  by  means  of  food  adapted  for 
respiration. 

How  different  is  the  energy  and  intensity 
of  vegetative  life  in  the  graminivora.  A 
cow,  or  a  sheep,  in  the  meadow,  eats,  almost 
without  interruption,  as  long  as  the  sun  is 
above  the  horizon.  Their  system  possesses 
the  power  of  converting  into  organized  tis- 
sues all  the  food  they  devour  beyond  the 
quantity  required  for  merely  supplying  the 
waste  of  their  bodies. 

All  the  excess  of  blood  produced  is  con- 
verted into  cellular  and  muscular  tissue;  the 
graminivorous  animal  becomes  fleshy  and 
plump,  while  the  flesh  of  the  carnivorous 
animal  is  always  tough  and  sinewy. 

If  we  consider  the  case  of  a  stag,  a  roe- 
deer,  or  a  hare,  animals  which  consume  the 
same  food  as  cattle  and  sheep,  it  is  evident 
that,  when  well  supplied  with  food,  their 
growth  in  size,  their  fattening,  must  depend 
on  the  quantity  of  vegetable  albumen,  fibrine, 
or  caseine,  which  they  consume.  With 
free  and  unimpeded  motion  and  exercise, 
enough  of  oxygen  is  absorbed  to  consume 
the  carbon  of  the  gum,  sugar,  starch,  and  of 
all  similar  soluble  constituents  of  their 
food. 

But  all  this  is  very  differently  arranged  in 
our  domestic  animals,  when  with  an  abun- 
dant supply  of  food,  we  check  the  processes 
of  cooling  and  exhalation,  as  we  do  when 
we  feed  them  in  stables,  where  free  motion 
is  impossible. 

The  stall-fed  animal  eats,  and  reposes 
merely  for  digestion.  It  devours  in  the 
shape  of  nitrogenized  compounds  far  more 
food  than  is  required  for  reproduction,  or  the 
supply  of  waste  alone ;  and  at  the  same 
time  it  eats  far  more  of  substances  devoid 
of  nitrogen  than  is  necessary  merely  to  sup- 
port respiration  and  to  keep  up  animal  heat. 
Want  of  exercise  and  diminished  cooling 
are-equivalent  to  a  deficient  supply  of  oxy- 
gen ;  for  when  these  circumstances  occur, 
the  animal  absorbs  much  less  oxygen  than 
is  required  to  convert  into  carbonic  acid 
the  carbon  of  the  substances  destined  for 
respiration.  Only  a  small  part  of  the  ex- 
cess of  carbon  thus  occasioned  is  ex- 
pelled from  the  body  in  the  horse  and  ox, 
in  the  form  of  hippuric  acid  ;  and  all  the  re- 
mainder is  employed  in  the  production  of  a 
substance  which,  in  the  normal  state,  only 
occurs  in  small  quantity  as  a  constituent 
of  the  nerves  and  brain.  This  substance 
is  fat. 

In  the  normal  condition,  as  to  exercise 
and  labour,  the  urine  of  the  horse  and  ox 
contains  benzoic  acid  (with  14  equivalents 
of  carbon  ;)  but  as  soon  as  the  animal  is 
kept  quiet  in  the  stable,  the  urine  con- 
tains hippuric  acid,  (with  18  equivalents 
of  carbon.) 

The  flesh  of  wild  animals  is  devoid  of 

fat;    while    thai    of    stall-fed     animals    is 

covered   with  that   substance.     When   the 

I  fattened  animal  is  allowed  to   move  rnor« 


ANIMAL   CHEMISTRY. 


freely  in  the  air,  or  compelled  to  draw  heavy 
ourdens,  the  fat  again  disappears. 

It  is  evident,  therefore,  that  the  formation 
of  fat  in  the  animal  body  is  the  result  of  a 
f  want  of  due  proportion    between  the  food 
/  taken  into  the  stomach  and  the  oxygen  ab- 
sorbed by  the  lungs  and  the  skin. 

A  pig,  when  fed  with  highly  nitrogenized 
food,  becomes  full  of  flesh;  when  fed  with 
potatoes  (starch)  it  acquires  little  flesh,  but 
a  ihick  layer  of  fat.  The  milk  of  a  cow, 
when  stall-fed,  is  very  rich  in  butter,  but  in 
the  meadow  is  found  to  contain  more  ca- 
seine,  and  in  the  same  proportion  less  butter 
and  sugar  of  milk.  In  the  human  female, 
beer,  and  farinaceous  diet  increase  the  pro- 
portion of  butter  in  the  milk;  an  animal  diet 
yields  less  milk,  but  it  is  richer  in  caseine. 

If  we  reflect,  that  in  the  entire  class  of 
carnivora,  the  food  of  which  contains  no 
substance  devoid  of  nitrogen  except  fat,  the 
production  of  fat  in  the  body  is  utterly  in- 
significant; that  even  in  these  animals,  as 
in  dogs  and  cats,  it  increases  as  soon  as  they 
live  on  a  mixed  diet;  and  that  we  can  in- 
crease the  formation  of  fat  in  other  domes- 
tic animals  at  pleasure,  but  only  by  means 
of  food  containing  no  nitrogen ;  we  can 
hardly  entertain  a  doubt  that  such  food,  in 
its  various  forms  of  starch,  sugar,  &c.,  is 
closely  connected  with  the  production  of  fat. 

In  the  natural  course  of  scientific  research, 
w-  draw  conclusions  from  the  food  in  re- 
£;<rd  to  the  tissues  or  substances  formed 
from  it;  from  the  nitrogenized  constituents 
of  plants  we  draw  certain  inferences  as  to 
the  nitrogenized  constituents  of  the  blood; 
and  it  is  quite  in  accordance  with  this,  the 
natural  method,  that  we  should  seek  to  es- 
tablish the  relations  of  tho^e  parts  of  our 
food  which  are  devoid  of  nitrogen  and  those 
parts  of  the  body  which  contain  none  of 
that  element.  It  is  impossible  to  over- 
look the  very  intimate  connexion  between 
them. 

If  we  compare  the  composition  of  sugar 
of  milk,  of  starch,  and  of  the  other  varieties 
of  sugar,  with  that  of  mutton  and  beef  suet 
and  of  human  fat,  we  find  that  in  all  of 
them  the  proportion  of  carbon  to  hydrogen 
is  the  same,  and  that  they  only  differ  in  that 
of  oxygen. 

According  to  the  analyses  of  Chevreul, 
mutton  fat,  human  fat,  and  hogs'  lard,  con- 
tain 29  percent,  of  carbon  to  11.1,  11.4, 
and  11.7  per  cent,  of  hydrogen  respec- 
tively. (16) 

Starch  contains  44.91  carbon  to  6.11 
hydrogen. 

Gutn  and  sugar  42.58  carbon  to  6.37 
hydrogen.  (17) 

It  is  obvious  that  these  numbers,  repre- 
senting the  relative  proportions  of  carbon 
and  hydrogen   in  starch,  gum,  and  sugar, 
are  in  the  same  ratio  as  the  carbon  and  hy- 
drogen in  the  different  kinds  of  fat;  for 
44-91    :   6-11  =79   :    10-99 
42-58   :    6-37  =  79   :    11-80 


From  which  it  follows,  that  sugar,  starch 
and  gum,  by  the  mere  separation  of  a  part 
of  their  oxygen,  may  pass  into  fat,  or  at 
least  into  a  substance  having  exactly  the 
composition  of  fat.  If  from  the  formula 
of  starch,  C12H10O10,  we  take  9  equivalents 
of  oxygen,  there  will  remain  in  100  parts  — 

C12  -  -  -  79-4 
H10  -  -  -  10-8 
O  -  -  -  9-8 

The  empirical  formula  of  fat  which  comes 
nearest  to  this  is  C"H10O,  which  gives  in 
100  parts— 

C»  -  -  -  78-9 
H">  -  -  .  11-6 
O  -  -  9-5 

According  to  this  formula,  an  equivalent 
of  starch,  in  order  to  be  changed  into  fat 
would  lose  1  equivalent  of  carbonic  acid, 
CO2,  and  7  equivalents  of  oxygen. 

Now  the  composition  of  all  saponifiable 
fatty  bodies  agrees  very  closely  with  one  or 
other  of  these  two  formulae. 

If  from  3  equivalents  of  sugar  of  milk, 


equivalents  of  water  and  31  of  oxygen,  there 
will  remain  C^H^O,  a  formula  which  ac- 
curately represents  the  composition  of  cho 
esterine,  the  fat  of  bile.  (18.) 

Whatever  views  we  may  entertain  re- 
garding the  origin  of  the  fatty  constituents 
of  the  body,  this  much  at  least  is  undeni- 
able, that  the  herbs  and  roots  consumed  by 
"he  cow  contain  no  butter;  that  in  hay  or 
:he  other  fodder  of  oxen  no  beef  suet  exists  ; 
hat  no  hogs'  lard  can  be  found  in  the  po- 
:ato  refuse  given  to  swine;  and  that  the  food 
of  geese  or  fowls  contains  no  goose  fat  or 
capon  fat.  The  masses  of  fat  found  in  the 
bodies  of  these  animals  are  formed  in  their 
organism;  and  when  the  full  value  of  this 
act  is  recognised,  it  entitles  us  to  conclude 
hat  a  certain  quantity  of  oxygen,  in  some 
orm  or  other,  separates  from  the  constitu- 
ents of  their  food;  for  without  such  a  sepa- 
ration of  oxygen,  no  fat  could  possibly  be 
ormed  from  any  one  of  these  substances. 

The  chemical  analysis  of  the  constituents 
of  the  food  of  the  gra'minivora  shows  in  the 
clearest  manner  that  they  contain  carbon 
and  oxygen  in  certain  proportions  ;  which, 

en  reduced  to  equivalents,  yield  the  fol- 
owing  series  :  — 

n  vegetable  fibrine,  albumen,  and  caseine, 

there  are  contained,  for 

1  20  eq.  carbon,  36  eq.  oxygen. 
n  starch  120  100 

n  cane  sugar    120  110 

ngum  120  110 

n  sugar  of  milk  120  120 

n  grape  sugar  120  140 

Now  in  all  fatty  bodies  there  are  contained, 
on  an  average  — 

For    -     120  eq.  carb.  only  10  eq.  oxygen. 

Since  the  carbon  of  the  fatty  constituents 
of  the  animal  body  is  derived  from  the  food 


FORMATION    OF    FAT. 


seeing  that  there  is  no  other  source  whence 
it  can  be  derived,  it  is  obvious,  if  we  sup- 
pose fat  to  be  formed  from  albumen,  fibrine, 
or  caseine,  that,  for  every  120  equivalents 
of  carbon  deposited  as  fat,  26  equivalents  of 
oxygen  must  be  separated  from  the  elements 
of  these  substances ;  and  further,  if  we  con- 
ceive fat  to  be  formed  from  starch,  sugar,  or 
sugar  of  milk,  that  for  the  same  amount  of 
carbon  there  must  be  separated  90,  100,  and 
110  equivalents  of  oxygen  from  these  com- 
pounds respectively. 

There  is,  therefore,  but  one  way  in  which 
the  formation  of  fat  in  the  animal  body  is 
possible,  and  this  is  absolutely  the  same  in 
which  its  formation  in  plants  takes  place ;  it 
is  a  separation  of  oxygen  from  the  elements 
of  the  food. 

The  carbon  which  we  find  deposited  in 
the  seeds  and  fruits  of  vegetables,  in  the  form 
of  oil  and  fat,  was  previously  a  constituent 
of  the  atmosphere,  and  was  absorbed  by  the 
plant  as  carbonic  acid.  Its  conversion  into 
fat  was  accomplished  under  the  influence  of 
light,  by  the  vital  force  of  the  vegetable ;  and 
the  greater  part  of  the  oxygen  of  this  car- 
bonic acid  was  returned  to  the  atmosphere 
as  oxygen  gas.* 

In  contradistinction  to  this  phenomenon 
ol  vitality  in  plants,  we  know  that  the  ani- 
mal system  absorbs  oxygen  from  the  atmo- 
sphere, and  that  this  oxygen  is  again  given 
out  in  combination  with  carbon  or  hydrogen ; 
we  know,  that  in  the  formation  of  carbonic 
acid  and  water,  the  heat  necessary  to  sus- 
tain the  constant  temperature  of  the  body  is 
produced,  and  that  a  process  of  oxidation  is 
the  only  source  of  animal  heat. 

Whether  fat  be  formed  by  the  decomposi- 
tion of  fibrine  and  albumen,  the  chief  con- 
stituents of  blood,  or  by  that  of  starch,  sugar, 
or  gum,  this  decomposition  must  be  accom- 
panied by  the  separation  of  oxygen  from  the 
elements  of  these  compounds.  But  this 
oxygen  is  not  given  out  in  the  free  state,  be- 
cause it  meets  in  the  organism  with  sub- 
stances possessing  the  property  of  entering 
into  combination  with  it.  In  fact,  it  is 
given  out  in  the  same  forms  as  that  which 
is  absorbed  from  the  atmosphere  by  the  skin 
and  lungs. 

It  is  easy  to  see,  from  the  above  consider- 
ations, that  a  very  remarkable  connexion 
exists  between  the  formation  of  fat  and  the 
respiratory  process. 

XVIII.  The  abnormal  condition,  which 
causes  the  deposit  of  fat  in  the  animal  body, 
depends,  as  was  formerly  stated,  on  a  dis- 
proportion between  the  quantity  of  carbon 
in  the  food  and  that  of  oxygen,  absorbed  by 
the  skin  and  lungs.  In  the  normal  condi- 
tion, the  quantity  of  carbon  given  out  is 
exactly  equal  to  that  which  is  taken  in  the 
food,  and  the  body  acquires  no  increase  of 
weight  from  the  accumulation  of  substances 
containing  much  carbon  and  no  nitrogen. 


*  See  Appendix,  No.  1 ),  on  the  formation  of 
MHX  and  honey  by  the  be;.    . 


If  we  increase  the  supply  of  highly  car- 
bonized food,  then  the  normal  state  can  only 
be  preserved  on  the  condition  that,  by  exer- 
cise and  labor,  the  waste  of  the  body  is  in- 
creased, and  the  supply  of  oxygen  aug- 
mented in  the  same  proportion. 

The  production  of  fat  is  always  a  conse- 
quence of  a  deficient  supply  of  oxygen,  for 
oxygen  is  absolutely  indispensable  for  the 
dissipation  of  the  excess  of  carbon  in  the 
food.  This  excess  of  carbon,  deposited  in 
the  form  of  fat,  is  never  seen  in  the  Bedouin 
or  in  the  Arab  of  the  desert,  who  exhibits 
with  pride  to  the  traveller  his  lean,  muscu- 
lar, sinewy  limbs,  altogether  free  from  fat; 
but  in  prisons  and  jails  it  appears  as  a  puf- 
finess  in  the  inmates,  fed,  as  they  are,  on  a 
poor  and  scanty  diet  ;  it  appears  in  the  se- 
dentary females  of  oriental  countries;  and 
finally,  it  is  produced  under  the  well  known 
conditions  of  the  fattening  of  domestic 
animals. 

The  formation  of  fat  depends  on  a  defi- 
ciency of  oxygen  ;  but  in  this  process,  in  the 
formation  of  fat  itself,  there  is  opened  up  a 
new  source  of  oxygen,  a  new  cause  of  ani- 
mal heat. 

The  oxygen  set  free  in  the  formation  of 
fat  is  given  out  in  combination  with  carbon 
or  hydrogen  ;  and  whether  this  carbon  and 
hydrogen  proceed  from  the  substance  that 
yields  the  oxygen,  or  from  other  compounds, 
still  there  must  have  been  generated  by  this 
formation  of  carbonic  acid  or  water  as  much 
heat  as  if  an  equal  weight  of  carbon  or  hydro- 
gen had  been  burned  in  air  or  in  oxygen  gas. 

If  we  suppose  that  from  2  equivalents  of 
starch  18  equivalents  of  oxygen  are  disen- 
gaged, and  that  these  18  equivalents  of  oxy- 
gen combine  with  9  equivalents  of  carbon, 
from  the  bile,  for  example,  no  one  can  doubt 
that,  in  this  case,  exactly  as  much  heat  must 
be  developed,  as  if  these  9  equivalents  of 
carbon  had  been  directly  burned.  In  this 
form,  therefore,  the  disengagement  of  heat 
as  a  consequence  of  the  formation  of  fat 
would  be  undeniable  ;  and  it  could  only  be 
considered  hypothetical,  on  the  supposition 
that  carbon  and  oxygen  were  disengaged 
from  one  and  the  same  substance,  in  the 
proportions  to  yield  carbonic  acid. 

If,  for  example,  we  suppose  that  from  2 
atoms  of  starch,  C^H^O20,  the  elements  of 
9  equivalents  of  carbonic  acid  are  separated, 
there  will  remain  a  compound  containing, 
for  15  equivalents  of  carbon,  20  of  hydrogen 
and  2  of  oxygen  ;  for 

=  C9O18  +  C15H*°O2. 


Or,  if  we  assume  that  oxygen  is  separated 
from  starch  in  the  form  both  of  carbonic 
acid  and  water,  then,  after  subtracting  the 
elements  of  6  equivalents  of  water  and  6  of 
carbonic  acid,  there  would  remain  the  com- 
pound C18H14O2;  for 

C24H2°O20  =  C6O12-f-  H6O6-}-  C18HwOa. 

Assuming,  then,  the  separation  of  oxygen 
in  either  of  these  forms,  it  remains  to  be  de- 
cided whether  the  carbonic  acid  and  water 


34 


ANIMAL   CHEMISTRY. 


given  off  were  contained,  as  such,  in  the 
starch,,  or  not. 

If  they  were  ready  formed  in  the  starch 
the  separation  might  occur  without  the  dis- 
engagement of  heat  ;  but  if  the  carbon  and 
hydrogen  were  present  in  any  other  form  in 
the  starch,  (or  in  the  compound  from  which 
the  fat  was  produced,)  it  is  obvious  that  a 
change  in  the  arrangement  of  the  atoms 
must  have  occurred,  in  consequence  of  which 
the  atoms  of  the  carbon  and  of  the  hydrogen 
have  united  with  those  of  the  oxygen,  to 
form  carbonic  acid  and  water. 

Now,  so  far  as  chemical  researches  have 
gone,  our  knowledge  of  the  constitution  of 
starch,  and  of  the  varieties  of  sugar,  will  justify 
no  other  conclusion  than  this,  that  these  sub- 
stances contain  no  ready  formed  carbonic  acid. 

We  are  acquainted  with  a  large  number 
of  processes  of  metamorphosis  of  a  similar 
kind,  in  which  the  elements  of  carbonic  acid 
and  water  are  separated  from  certain  pre- 
existing compounds;  and  we  know  with 
certainty  that  all  these  processes  are  accom- 
panied by  a  disengagement  of  heat,  exactly 
as  if  the  carbon  and  hydrogen  combined 
directly  with  oxygen. 

Such  a  disengagement  of  carbonic  acid, 
for  example,  occurs  in  all  processes  of  fer- 
mentation or  putrefaction,  which  are,  with- 
out exception,  accompanied  with  a  genera- 
tion of  heat. 

In  the  fermentation  of  a  saccharine  solu- 
tion, in  consequence  of  a  new  arrangement 
of  the  elements  of  the  sugar,  a  certain  part 
of  its  carbon  and  oxygen  unite  to  form  car- 
bonic acid,  which  separates  as  gas;  and  as 
another  result  of  this  decomposition,  we  ob- 
tain a  volatile  combustible  liquid,  containing 
little  oxygen,  namely,  alcohol. 

If  we  add  to  2  equivalents  of  sugar  the 
elements  of  12  equivalents  of  water,  and 
subtract  from  the  sum  of  the  atoms  24  equi- 
valents of  oxygen,  there  remain  6  equiva- 
lents of  alcohol. 

—  O24  =  C"H36Ol*=  6 
eq.  alcohol. 

These  24  equivalents  of  oxygen  suffice  to 
oxidize  completely  a  third  equivalent  of 
sugar  —  that  is,  to  convert  its  carbon  into 
carbonic  acid  and  its  hydrogen  into  water, 
and  by  this  oxidation  we  recover  the  12 
equivalents  of  water  supposed  to  be  added 
in  the  former  part  of  the  process,  exactly  as 
if  this  water  had  taken  no  share  in  it. 


C12H12O12+O24=  ISCO2^  12HO. 

According  to  the  ordinary  view,  12  equi- 
valents of  carbonic  acid  separate  from  3  of 
sugar,  yielding  6  of  alcohol  —  that  is,  exactly 
the  same  amount  of  these  products  as  if  two- 
thirds  of  the  sugar  had  yielded  oxygen  to  the 
remaining  third,  so  as  completely  to  oxidize 
'ts  elements. 

C36H36O36=C3*H86O12+  12COa  * 

*  For  an  explanation  of  the  formulae  and  equa- 
tions employed,  see  the  Introduction  to  the  Ap- 
pendix. 


By  a  comparison  of  tl.ese  two  methods  of 
representing  the  same  cnange,  it  will  easily 
b'e  seen  that  the  division  or  splitting  of  a 
compound  like  sugar  into  carbonic  acid,  on 
the  one  hand,  and  a  compound  containing  a 
little  oxygen  on  the  other,  is  in  its  results 
perfectly  equivalent  to  a  separation  of  oxy- 
gen from  a  certain  portion  of  the  compound, 
and  the  oxidation  or  combustion  of  another 
portion  of  it  at  the  expense  of  this  oxy- 
gen. 

It  is  well  known  that  the  temperature  of 
a  fermenting  liquid  rises  ;  and  if  we  assurna 
that  a  hogshead  of  wort,  holding  1,200  litres 
=  2,400  Ibs.,  French  weight,  contains  16 
per  cent,  of  sugar,  in  all  384  Ibs.,  then,  dur- 
ing the  fermentation  of  this  sugar,  an  amount 
of  heat  must  be  generated  equal  to  that 
which  would  be  produced  by  the  combus- 
tion of  51  Ibs.  of  carbon. 

This  is  equal  to  a  quantity  of  heat  by 
which  every  pound  of  the  liquid  might  be 
heated  by  297-9°;  that  is,  supposing  the 
decomposition  of  the  sugar  to  occur  in  a 
period  of  time  too  short  to  be  measured. 
This  is  well  known  not  to  be  the  case ;  the 
fermentation  lasts  five  or  six  days,  and  each 
pound  of  liquid  receives  the  207-9  degrees 
of  heat  during  a  period  of  120  hours.  In 
each  hour  there  is,  therefore,  set  free  an 
amount  of  heat  capable  of  raising  the  tem- 
perature of  each  pound  of  liquid  1-4  degree; 
a  rise  of  temperature  which  is  very  power- 
fully counteracted  by  external  cooling  and 
by  the  vaporization  of  alcohol  and  water. 

The  formation  of  fat,  like  other  analogous 
phenomena  in  which  oxygen  is  separated 
in  the  form  of  carbonic  acid,  is  consequently 
accompanied  by  a  disengagement  of  heat. 
This  change  supplies  to  the  animal  body  a 
certain  proportion  of  the  oxygen  indispens- 
able to  the  vital  processes;  and  this  espe- 
cially in  those  cases  in  which  the  oxygen 
absorbed  by  the  skin  and  lungs  is  not  suf- 
ficient to  convert  into  carbonic  acid  the 
whole  of  the  carbon  adapted  for  this  com 
bination. 

This  excess  of  carbon,  as  it  cannot  be 
employed  to  form  a  part  of  any  organ,  is 
deposited  in  the  cellular  tissue  in  the  form 
of  tallow  or  oil. 

At  every  period  of  animal  life,  when  there 
occurs  a  disproportion  between  the  carbon 
of  the  food  and  the  inspired  oxygen,  the 
latter  being  deficient,  fat  must  be  formed. 
Oxygen  separates  from  existing  compounds, 
and  this  oxygen  is  given  out  as  carbonic  acid 
or  water.  The  heat  generated  in  the  forma- 
tion of  these  two  products  contributes  to 
seep  up  the  temperature  of  the  body. 

Every  pound  of  carbon  which  obtains  the 
oxygen  necessary  to  convert  it  into  carbonic 
acid  from  substances  which  thereby  pass 
into  fat,  must  disengage  as  much  heat  as 
would  raise  the  temperature  of  200  Ibs.  of 
water  by  70°, — that  is,  from  32°  to  102°. 

Thus,  in  the  formation  of  fat,  the  vital 
*orce  possesses  a  means  of  counteracting  a 
deficiency  in  the  supply  of  oxygen,  and  con- 


FORMATION   OF   FAT. 


35 


sequently  in  that  of  the  heat  indispensable 
for  the  vital  process. 

Experience  teaches  us  that  in  poultry, 
the  maximum  of  fat  is  obtained  by  tying 
the  feet,  and  by  a  medium  temperature. 
These  animals  in  such  circumstances  may 
be  compared  to  a  plant  possessing  in  the 
highest  degree  the  power  of  converting  all 
food  into  parts  of  its  own  structure.  The 
excess  of  the  constituents  of  blood  forms 
flesh  and  other  organized  tissues,  while  that 
of  starch,  sugar,  &c.,  is  converted  into  fat. 
When  animals  are  fattened  on  food  destitute 
of  nitrogen,  only  certain  parts  of  their  struc- 
ture increase  in  size.  Thus,  in  a  goose, 
fattened  in  the  method  above  alluded  to,  the 
liver  becomes  three  or  four  times  larger  than 
in  the  same  animal,  when  well  fed  with  free 
motion,  while  we  cannot  say  that  the  or- 
ganized structure  of  the  liver  is  thereby  in- 
creased. The  liver  of  a  goose  fed  in  the 
ordinary  way  is  firm  and  elastic;  that  of  the 
imprisoned  animal  is  soft  and  spongy.  The 
difference  consists  in  a  greater  or  less  ex- 
pansion of  its  cells  which  are  rilled  with  fat. 

In  some  diseases,  the  starch,  sugar,  &,c., 
of  the  food  obviously  do  not  undergo  the 
changes  which  enable  them  to  assist  in 
respiration,  and  consequently  to  be  con- 
verted into  fat.  Thus,  in  diabetes  mellitus, 
the  starch  is  only  converted  into  grape  sugar, 
which  is  expelled  from  the  body  without 
further  change. 

In  other  diseases,  as  for  example  in  in- 
flammation of  the  liver,  we  find  the  blood 
loaded  with  fat  and  oil;  and  in  the  composi- 
tion of  the  bile  there  is  nothing  at  all  incon- 
sistent with  the  supposition  that  some  of  its 
constituents  may  be  transformed  into  fat. 

XIX.  According  to  what  has  been  laid 
down  in  the  preceding  pages,  the  substances 
of  which  the  food  of  man  is  composed  may 
be  divided  into  two  classes ;  into  hitrogenized 
&n([lfion-nitrogenized.     The  former  are  ca- 
pable of  conversion  into  blood;  the  latter 
incapable  of  this  transformation. 

Out  of  those  substances  which  are  adapted 
to  the  formation  of  blood  are  formed  all  the 
organized  tissues.     The  other  class  of  sub- 
stances, in  the  normal  state  of  health,  serve 
to  support  the  process  of  respiration.     The 
former  may  be  called  the  plastic  dements  of 
nutrition;  the  latter,  elements  of  respiration. 
Among  the  former  we  reckon — 
Vegetable  fibrine. 
Vegetable  albumen. 
Vegetable  caseine. 
Animal  flesh. 
Animal  blood. 

Among  the  elements  of  respiration  in  our 
food,  are — 

Fat.  Pectine. 

Starch.  Bassorine. 

Gum.  Wine. 

Cane  Sugai.  Beer. 

Grape  Sugar.  Spirits. 

Sugar  of  milk. 

XX.  The   most    recent    and    exact  re- 
searches  have   established   as   a  universal 


fact,  to  which  nothing  yet  known  is  op- 
posed, that  the  nitrogenized  constituents  of 
vegetable  food  have  a  composition  identical 
with  that  of  the  constituents  of  the  blood. 

No  nitrogenized  compound,  the  compos] 
tion  of  which  differs  from  that  of  fibrine 
albumen,  and  caseine,  is  capable  of  sup- 
porting the  vital  process  in  animals. 

The  animal  organism  unquestionably  pos\ 
sesses  the  power  of  forming,  from  the  con 
slituents  of  its  blood,  the  substance  of  it: 
membranes  and  cellular  tissue,  of  the  nerve; 
and  brain,  of  the  organic  part  of  cartilages 
and  bones.  But  the  blood  must  be  suppliec 
to  it  ready  formed  in  every  thing  but  its 
form — that  is,  in  its  chemical  composition. 
If  this  be  not  done,  a  period  is  rapidly  put 
to  the  formation  of  blood,  and  consequently 
to  life. 

This  consideration  enables  us  easily  to 
explain  how  it  happens  that  the  tissues 
yielding  gelatine  or  chondrine,  as,  for  ex- 
ample, the  gelatine  of  skin  or  of  bones,  are 
not  adapted  for  the  support  of  the  vital  pro- 
cess ;  for  their  composition  is  different  from 
that  of  fibrine  or  albumen.  It  is  obvious 
that  this  means  nothing  more  than  that  those 
parts  of  the  animal  organism  which  form 
the  blood  do  not  possess  the  power  of  effect- 
ing a  transformation  in  the  arrangement  of 
the  elements  of  gelatine,  or  of  those  tissues 
which  contain  it.  The  gelatinous  tissues, 
the  gelatine  of  the  bones,  the  membranes, 
the  cells,  and  the  skin,  suffer,  in  the  animal 
body,  under  the  influence  of  oxygen  and 
moisture,  a  progressive  alteration;  a  part 
of  these  tissues  is  separated,  and  must  be 
restored  from  the  blood  ;  but  this  alteration 
and  restoration  is  obviously  confined  within 
very  narrow  limits. 

While,  in  the  body  of  a  starving  or  sick 
individual,  the  fat  disappears,  and  the  mus- 
cular tissue  takes  once  more  the  form  of 
blood,  we  find  that  the  tendons  and  mem- 
branes retain  their  natural  condition ;  the 
limbs  of  the  dead  body  retain  their  connex- 
ions, which  depend  on  the  gelatinous  tis- 
sues. 

On  the  other  hand,  we  see  that  the  gelatine 
of  bones  devoured  by  a  dog  entirely  disap- 
pears, while  only  the  bone  earth  is  found  in 
his  excrements.  The  same  is  true  of  man, 
when  fed  on  food  rich  in  gelatine,  as,  for 
example,  strong  soup.  The  gelatine  is  not 
to  be  found  either  in  the  urine  or  in  the 
faeces,  and  consequently  must  have  under- 
gone a  change,  and  must  have  served  some 
purpose  in  the  animal  economy.  It  is  clear, 
that  the  gelatine  must  be  expelled  from  the 
body  in  a  form  different  from  that  in  which 
it  was  introduced  as  food. 

When  we  consider  the  transformation  of 
the  albumen  of  the  blood  into  a  part  of  an 
organ  composed  of  fibrine,  the  identity  in 
composition  of  the  two  substances  renders 
the  change  easily  conceivable.  Indeed  we 
find  the  change  of  a  dissolved  substance  into 
an  insoluble  organ  of  vitality,  chemically 
speaking,  natural  and  easily  explained,  or 


.    36 


ANIMAL   CHEMISTRY. 


account  of  this  very  identity  of  composition. 
Hence  the  opinion  is  not  unworthy  of  a 
closer  investigation,  that  gelatine,  when 
taken  in  the  dissolved  state,  is  again  con- 
verted, in  the  body,  into  cellular  tissue, 
membrane  and  cartilage;  that  it  may  serve 
for  the  reproduction  of  such  parts  of  these 
tissues  as  have  been  wasted,  and  for  their 
growth. 

And  when  the  powers  of  nutrition  in  the 
whole  body  are  affected  by  a  change  of  the 
health,  then,  even  should  the  power  of  form- 
ing blood  remain  the  same,  the  organic  force 
by  which  the  constituents  of  the  blood  are 
/transformed  into  cellular  tissue  and  mem- 
branes must  necessarily  be  enfeebled  by 
sickness.  In  the  sick  man,  the  intensity  of 
the  vital  force,  its  power  to  produce  meta- 
morphoses, must  be  diminished  as  well  in 
the  stomach  as  in  all  other  parts  of  the  body. 


In  this  condition,  the  uniform  experience  of 
practical  physicians  shows  that  gelatinous 
matters  in  a  dissolved  state  exercise  a  most 
decided  influence  on  the  state  of  the  health. 
Given  in  a  form  adapted  for  assimilation, 
they  serve  to  husband  the  vital  force,  just 
as  may  be  done,  in  the  case  of  the  stomach, 
by  due  preparation  of  the  food  in  general. 
Brittleness  in  the  bones  of  graminivorous 
animals  is  clearly  owing  to  a  weakness  in 
those  parts  of  the  organism  whose  function 
it  is  to  convert  the  constituents  of  the  blood 
into  cellular  tissue  and  membrane  ;  and  if 
we  can  trust  to  the  reports  of  physicians 
who  have  resided  in  the  East,  the  Turkish 
women,  in  their  diet  of  rice,  and  in  the  fre- 
quent use  of  enemata  of  strong  sotfp,  have 
united  the  conditions  necessary  for  the 
formation  both  of  cellular  cissue  and  of 
fat. 


PART  II. 

THE  METAMORPHOSIS  OF  TISSUES. 


1.  THE  absolute  identity  of  composition 
in  the  chief  constituents  of  blood  and  the  ni- 
trogen ked    compounds    in   vegetable   food 
would,  some  years  ago,  have  furnished  a 
plausible  reason  for  denying  the  accuracy  of 
the  chemical  analysis  leading  to  such  a  re- 
sult.    At  that  period,  experiment  had  not  as 
yet  demonstrated  the  existence  of  numerous 
compounds,  both  containing  nitrogen  and 
devoid   of  that  element,   which   with   the 
greatest  diversity  in  external  characters,  yet 
possess  the  very  same  composition  in  100 
parts;  nay,  many  of  which  even  contain  the 
same  absolute  amount  of  equivalents  of  each 
element.     Such  examples  are  now  very  fre- 
quent, and   are  known  by  the  names  of 
isomeric  and  polymeric  compounds. 

2.  Cyanuric  acid,  for  example,  is  a  nitro- 
genized   compound  which   crystallizes    in 
beautiful  transparent  octahedrons,  easily  so- 
luble in  water  and  in  acids,  and  very  per- 
manent.    Cyamelide  is  a  second  body,  abso- 
lutely insoluble  in  water  and  acids,  white 
and   opaque    like    porcelain    or   magnesia. 
Hydrated  cyanic  acid  is  a  third  compound, 
which  is  a  liquid  more  volatile  than  pure 
acetic  acid,  which  blisters  the  skin,  and  can- 
not be  brought  in  contact  with  water  with- 
out being  instantaneously  resolved  into  new 
products.     These  three  substances  not  only 
yield,  on  analysis,  absolutely  the  same  rela- 
tive weights  of  the  same  elements.!  but  they 
may  be  converted  and  reconverted  into  one 
another,  even  in  hermetically  closed  vessels 
— that  is,  without  the   aid  of  any  foreign 
matter.  (See  Appendix,  21.)  Again,  among 
those  substances  which  contain  no  nitrogen, 
we  have  aldehyde,  a  combustible  liquid  mis- 
cible  with  water,  which  boils  at  the  tempe- 
rature of  the  hand,  attracts  oxygen  from  the 
atmosphere   with   avidity,  and   is   thereby 


changed  into  acetic  acid.  Tins  compound 
cannot  be  preserved,  even  in  close  vessels  : 
for  after  some  hours  or  days,  its  consistence, 
its  volatility,  and  its  power  of  absorbing 
oxygen,  all  are  changed.  It  deposits  long, 
hard,  needle-shaped  crystals,  which  at  212° 
are  not  volatilized,  and  the  supernatant  liquid 
is  no  longer  aldehyde.  It  now  boils  at  140°, 
cannot  be  mixed  with  water,  and  when 
cooled  to  a  moderate  degree  crystallizes  in  a 
form  like  ice.  Nevertheless,  analysis  has 
proved,  that  these  three  bodies,  so  different 
in  their  characters,  are  identical  in  composi- 
tion. (21.) 

3.  A  similar  group  of  three  occurs  in  the 
case  of  albumen,  fibrine,  and  caseine.  They 
differ  in  external  character,  but  contain 
exactly  the  same  proportions  of  organic  ele- 
ments. 

When  animal  albumen,  fibrine,  and  ca- 
seine are  dissolved  in  a  moderately  strong 
solution  of  caustic  potash,  and  the  solution 
is  exposed  for  some  time  to  a  high  tempera- 
ture, these  substances  are  decomposed.  The 
addition  of  acetic  acid  to  the  solution  causes, 
in  all  three,  the  separation  of  a  gelatinous 
translucent  precipitate,  which  has  exactly 
the  same  characters  and  composition,  from 
whichever  of  the  three  substances  above 
mentioned  it  has  been  obtained. 

Mulder,  to  whom  we  owe  the  discovery 
of  this  compound,  found,  by  exact  and  care- 
ful analysis,  that  it  contains  the  same  organic 
elements,  and  exactly  in  the  same  propor- 
tion, as  the  animal  matters  from  which  it  is 
prepared  ;  insomuch,  that  if  we  deduct  from 
the  analysis  of  albumen,  fibrine,  and  caseine, 
the  ashes  they  yield  when  incinerated,  as 
well  as  the  sulphur  and  phosphorus  they 
contain,  and  then  calculate  the  remainder 
for  100  parts,  we  obtain  the  same  result  an 


DIGESTION   COMPARED   TO   FERMENTATION. 


37 


in  the  analysis  of  the  precipitate  above  de- 
scribed, prepared  by  potash,  which  is  free 
from  inorganic  matter.  (22.) 

Viewed  in  this  light,  the  chief  constituents 
of  the  blood  and  the  caseine  of  milk  may  be 
regarded  as  compounds  of  phosphates  and 
other  salts,  and  of  sulphur  and  phosphorus, 
with  a  compound  of  carbon,  nitrogen,  hy- 
drogen, and  oxygen,  in  which  the  relative 
proportion  of  these  elements  is  invariable; 
and  this  compound  may  be  considered  as  the 
commencement  and  starting  point  of  all 
other  animal  tissues,  because  these  are  all 
produced  from  the  blood. 

These  considerations  induced  Mulder  to 
give  to  this  product  of  the  decomposition  of 
albumen,  &c.,  by  potash,  the  name  of  pro- 
teine (from  jrgomy*,  "  I  take  the  first  rank.") 
The  blood,  or  the  constituents  of  the  blood, 
are  consequently  compounds  of  this  proteine 
with  variable  proportions  of  inorganic  sub- 
stances. 

Mulder  further  ascertained,  that  the  in- 
soluble nitrogenized  constituent  of  wheat 
flour  (vegetable  fibrine,)  when  treated  with 
potash,  yields  the  very  same  product,  pro- 
teine; and  it  has  recently  been  proved  that 
vegetable  albumen  and  caseine  are  acted  on 
by  potash  precisely  as  animal  albumen  and 
caseine  are. 

4.  As  far,  therefore,  as  our  researches 
have  gone,  it  may  be  laid  down  as  a  law, 
founded  on  experience,  that  vegetables  pro- 
duce, in  their  organism,  compounds  of  pro- 
teine ;  and  that  put  of  these  compounds  of 
proteine  the  various  tissues  and  parts  of  the 
animal  body  are  developed  by  the  vital  force, 
with  the  aid  of  the  oxygen  of  the  atmosphere 
and  of  the  elements  of  water.* 

Now,  although  it  cannot  be  demonstrated 
that  proteine  exists  ready  formed  in  these 
vegetable  and  animal  products,  and  although 
the  difference  in  their  properties  seems  to  in- 
dicate that  their  elements  are  not  arranged 
in  the  same  manner,  yet  the  hypothesis  of 
the  pre-existence  of  proteine,  as  a  point  of 
departure  in  developing  and  comparing  their 
properties,  is  exceedingly  convenient*  At 
all  events  it  is  certain  that  the  elements  of 
these  compounds  assume  the  same  arrange- 
ments when  acted  on  by  potash  at  a  higli 
temperature. 

All  the  organic  nitrogenized  constituents 
of  the  body,  how  different  soever  they  may 
be  iu  composition,  are  derived  from  proteine. 
They  are  formed  from  it,  by  the  addition  or 
subtraction  of  the  elements  of  water  or  of 
oxygen,  and  by  resolution  into  two  or  more 
compounds. 

*  The  experiment  of  Tiedemann  and  Gmelin, 
who  found  it  impossible  to  sustain  the  life  of  geese 
by  means  of  boiled  white  of  egg,  may  be  easily 
explained,  when  we  reflect  that  a  graminivorous 
animal,  especially  when  deprived  of  free  motion, 
cannot  obtain,  from  the  transformation  or  waste 
of  the  tissues  alone,  enough  of  carbon  for  the  re- 
spiratory process.  2  Ibs.  of  albumen  contain  only 
3^  oz.  of  carbon,  of  which,  among  the  last  pro- 
ittcts  of  transformation,  a  fourth  part  is  given  off 
in  he  form  of  uric  acid. 


5.  This  proposition  must   be  received  as 
an  undeniable  truth,  when  we  reflect  on  the 
developement  of  the  young  animal  in  the 
egg  of  a  fowl.     The  egg  can  be  shown  to 
contain  no  other  nitrogenized  compound  ex- 
cept albumen.     The  albumen  of  the  yolk  is 
identical   with  that  of  the  white ;  (23)  the 
yolk  contains,  besides,  only  a  yellow  fat,  in 
which  cholesterine  and  iron  may  be  detected. 
Yet  we  see  in  the  process  of  incubation, 
during  which  no  food  and  no  foreign  matter, 
except  the  oxygen  of  the  air,  is  introduced, 
or  can  take  part  in  the  developement  of  the 
animal,  that  out  of  the  albumen,  feathers, 
claws,  globules  of  the  blood,  fibrine,  mem- 
brane and  cellular  tissue,  arteries  and  veins, 
are  produced.    The  fat  of  the   yolk  may 
have  contributed,  to  a  certain  extent,  to  the 
formation  of  the  nerves  and  brain ;  but  the 
carbon  of  this   fat  cannot   have  been  em- 
ployed to  produce  the  organized  tissues  in 
which  vitality  resides,  because  the  albumen 
of  the  white  and  of  the  yolk  already  con- 
tains, for  the  quantify  of  nitrogen   present, 
exactly  the  proportion  of  carbon  required 
for  the  formation  of  these  tissues. 

6.  The  true   starting-point    for    all    the 
tissues  is,  consequently,  albumen;    all  ni- 
trogenized   articles    of   food,   whether    de- 
rived from  the  animal  or  from  the  vegeta- 
ble  kingdom,  are  converted  into  albumen 
before  they  can  take  part  in  the  process  of 
nutrition. 

All  the  food  consumed  by  an  animal  be- 
comes in  the  stomach  soluble,  and  capable 
of  entering  into  the  circulation.  In  the  pro- 
cess by  which  this  solution  is  effected,  only 
one  fluid,  besides  the  oxygen  of  the  air, 
takes  a  part ;  it  is  that  which  is  secreted  by 
the  lining  membrane  of  the  stomach. 

The  most  decisive  experiments  of  physio- 
logists have  shown  that  the  process  of 
chymification  is  independent  of  the  vital 
force ;  that  it  takes  place  in  virtue  of  a  purely 
chemical  action,  exactly  similar  to  those 
processes  of  decomposition  or  transforma- 
tion which  are  known  as  putrefaction,  fer- 
mentation or  decay  (eremacausis). 

7.  When  expressed  in  the  simplest  form, 
fermentation,  or  putrefaction,  may  be  de- 
scribed as  a  process  of  transformation — that 
is,  a  new  arrangement  of  the   elementary- 
particles,  or  atoms,  of  a  compound,  yielding 
two  or  more  new  groups  or  compounds,  and 
caused    by  contact  with  other  substances, 
the  elementary  particles  of  which  are  them- 
selves in  a  state  of  transformation  or  decom- 
position.    It  is  a  communication,  or  an  im- 
parting of  a  state  of   motion,  which  the 
atoms  of  a  body  in  a  state  of  motion  are  ca- 
pable of  producing1  in  other  bodies,  whose 
elementary  particles  are  held  together  only 
by  a  feeble  attraction. 

8.  Thus  the  clear  gastric  juice  contains  a 
substance  in  a  state  of  transformation,  by 
the  contact  of  which  with  those  constituents 
of  the  food  which,  by  themselves,  are  in- 
soluble in  water,  the  latter  acquire,  in  virtue 
of  a  new  grouping  of  their  atoms,  the  pro- 


38 


ANIMAL   CHEMISTRY. 


perty  of  dissolving  in  that  fluid.  During  \ 
digestion,  the  gastric  juice,  when  separated,  I 
is  found  to  contain  a  free  mineral  acid,  the  ' 
presence  of  which  checks  all  further  change. 
That  the  food  is  rendered  soluble  quite  inde- 
pendently of  the  vitality  of  the  digestive 
organs  has  been  proved  by  a  number  of  the 
most  beautiful  experiments.  Food,  enclosed 
in  perforated  metallic  tubes,  so  that  it  could 
not  come  into  contact  with  the  stomach, 
was  found  to  disappear  as  rapidly,  and  to  be 
as  perfectly  digested,  as  if  the  covering  had 
been  absent;  and  fresh  gastric  juice,  out  of 
the  body,  when  boiled  white  of  egg,  or  mus- 
cular fibre,  were  kept  in  contact  with  it  for 
a  time  at  the  temperature  of  the  body, 
caused  these  substances  to  lose  the  solid 
form  and  to  dissolve  in  the  liquid. 

9.  It  can  hardly  be  doubted  that  the  sub- 
stance which  is  present  in  the  gastric  juice 
in  a  state  of  change  is  a  product  of  the  trans- 
formation of  the  stomach   itself.     No  sub- 
stances possess,  in  so  high  a  degree  as  those 
arising  from  the  progressive  decomposition 
of  the  tissues  containing  gelatine  or  chon- 
drine,  the  property  of  exciting  a  change  in 
the  arrangement  of  the  elements  of  other 
compounds.     When  the  lining  membrane 
of  the  stomach  of  any  animal,  as,  for  ex- 
ample, that  of  the  calf,  is  cleaned  by  con- 
tinued washing  with  water,  it  produces  no 
effect  whatever,  if  brought  into  contact  with 
a  solution  of  sugar,  with  milk  or  other  sub- 
stances.    But  if  the  same  membrane  be  ex- 
posed for  some  time  to  the  air,  or  dried,  and 
then  placed  in  contact  with  such  substances, 
the  sugar  is  changed,  according  to  the  state 
of   decomposition  of   the    animal    matter, 
either  into  lactic  acid,  into  mannite  and  mu- 
cilage, or  into  alcohol  and  carbonic  acid; 
while  milk  is  instantly  coagulated.     An  or- 
dinary animal  bladder  retains,  when  dry,  all 
its   properties    unchanged;    but   when   ex- 
posed to  air  and  moisture,  it   undergoes  a 
change  not  indicated  by  any  obvious  exter- 
nal signs.     If,  in  this  state,  it  be  placed  in  a 
solution  of  sugar  of  milk,  that  substance  is 
quickly  changed  into  lactic  acid. 

10.  The  fresh  lining  membrane  of  the 
stomach  of  a  calf,  digested  with  weak  mu- 
riatic acid,  gives  to  this  fluid  no  power  of 
dissolving  boiled  flesh  or  coagulated  white 
of  egg.     But  if  previously  allowed  to  dry, 
or  if  left  for  a  time  in  water,  it  then  yields, 
to  water  acidulated  with  muriatic  acid,  a 
substance  in  minute  quantity,  the  decompo- 
sition of  which  is  already  commenced,  and 
is  completed  in  the  solution.    If  coagulated 
albumen  be  placed  in  this  solution,  the  state 
of  decomposition   is   communicated   to   it, 
first  at  the  edges,  which  become  translucent, 
pass  into  a  mucilage,  and  finally  dissolve. 
The    same  change    gradually    affects    the 
whole  mass,  and  at   last   it  is  entirely  dis- 
solved, with  the  exception  of  fatty  particles, 
which  render  the  solution  turbid.     Oxygen 
is  conveyed  to  every  part  of  the  body  by  the 
arterial  blood ;  moisture  is  every  where  pre- 
sent;  and  thus  we  have  united  the  chief 


conditions  of  all  transformations  in  the  ani- 
mal body. 

Thus,  as  in  the  germination  of  seeds,  the 
presence  of  a  body  in  a  state  of  decomposi- 
tion or  transformation,  which  has  been 
called  diastase,  effects  the  solution  of  the 
starch — that  is,  its  conversion  into  sugar ; 
so,  a  product  of  the  metamorphosis  of  the 
substance  of  the  stomach,  being  itself  in  a 
state  of  metamorphosis  which  is  completed 
in  the  stomach,  effects  the  dissolution  of  all 
such  parts  of  the  food  as  are  capable  of  as- 
suming a  soluble  form.  In  certain  diseases, 
there  are  produced  from  the  starch,  sugar, 
&c.,  of  the  food,  lactic  acid  and  mucilage. 
(24.)  These  are  the  very  same  products 
which  we  can  produce  out  of  sugar  by 
means  of  membrane  in  a  state  of  decompo- 
sition out  of  the  body ;  but  in  a  normal  state 
of  health,  no  lactic  acid  is  formed  in  the 
stomach. 

11.  The  property  possessed  by  many  sub- 
stances, such  as  starch  and  the  varieties  of 
sugar,  by  contact  with  animal  substances  in 
a  state  of  decomposition,  to  pass  into  lactic 
acid,  has  induced  physiologists,  without 
farther  inquiry,  to  assume  the  fact  of  the 
production  of  lactic  acid  during  digestion 
and  the  power  which  this  acid  has  of  dis- 
solving phosphate  of  lime  has  led  them  t< 
ascribe  to  it  the  character  of  a  general  sol 
vent.  But  neither  Prout  nor  Braconno 
could  detect  lactic  acid  in  the  gastric  juice, 
and  even  Lehmann  (see  his  "  Lehrbuch  der 
Physiologischen  Chemie,"  torn.  i.  p.  285) 
obtained  from  the  gastric  juice  of  a  cat  only 
microscopic  crystals,  which  he  took  for  lac- 
tate  of  zinc,  although  their  chemical  cha- 
racter could  not  be  ascertained.  The  pre- 
sence of  free  muriatic  acid  in  the  gastric 
juice,  first  observed  by  Prout,  has  been  con- 
firmed by  all  those  chemists  who  have  ex- 
amined that  fluid  since.  This  muriatic  acid 
is  obviously  derived  from  common  salt,  the 
soda  of  which  plays  a  very  decided  part  in 
the  conversion  of  fibrine  and  caseine  into 
blood. 

Muriatic  acid  yields  to  no  other  acid  in 
the  power  of  dissolving  bone  earth,  and 
even  acetic  acid,  in  this  respect,  is  equal  to 
lactic  acid.  There  is  consequently  no  proof 
of  the  necessity  of  lactic  acid  in  the  diges- 
tive process ;  and  we  know  with  certainty, 
that  in  artificial  digestion  it  is  not  formed. 
Berzelius  indeed  has  found  lactic  acid  in  the 
blood  and  flesh  of  animals ;  but  when  his 
experiments  were  made,  chemists  were 
ignorant  of  the  extraordinary  facility  and 
rapidity  with  which  this  acid  is  formed 
from  a  number  of  substances  containing  its 
elements,  when  in  contact  with  animal 
matter. 

In  the  gastric  juice  of  a  dog,  Braconnot 
found,  along  with  free  muriatic  acid,  distinct 
traces  of  a  salt  of  iron,  which  he  at  first 
held  to  be  an  accidental  admixture.  But  in 
the  gastric  juice  of  a  second  dog,  collected 
with  the  utmost  care,  the  iron  was  again 
found.  (Ann.  de  Ch.  et  de  Ph.  lix.  p.  249. 


NITROGEN   EXHALED   FROM  THE   LUNGS. 


39 


This  occurrence  of  iron  is  full  of  signifi- 
cance in  regard  to  the  formation  of  the 
blood. 

12.  In  the  action  of  the  gastric  juice  on 
the  food,  no  other  element  takes  a  share, 
except  the  oxygen  of  the  atmosphere  and 
the  elements  of  water.  This  oxygen  is  in- 
troduced directly  into  the  stomach.  During 
the  mastication  of  the  food,  there  is  secreted 
into  the  mouth  from  organs  specially  des- 
tined to  this  function,  a  fluid,  the  saliva, 
which  possesses  the  remarkable  property  of 
enclosing  air  in  the  shape  of  froth,  in  a  far 
higher  degree  than  even  soapsuds.  This 
air,  by  means  of  the  saliva,  reaches  the  sto- 
mach with  the  food,  and  there  its  oxygen 
enters  into  combination,  while  its  nitrogen 
is  given  out  through  the  skin  and  lungs. 
The  longer  digestion  continues,  that  is,  the 
greater  resistance  offered  to  the  solvent  ac- 
tion by  the  food,  the  more  saliva,  and  con- 
sequently the  more  air  enters  the  stomach. 
Rumination,  in  certain  graminivorous  ani- 
mals, has  plainly  for  one  object  a  renewed 
and  repeated  introduction  of  oxygen;  for 
a  more  minute  mechanical  division  of  the 
food  only  shortens  the  time  require  I  for 
solution. 

The  unequal  quantities  of  air  which  reach 
the  stomach  with  the  saliva  in  different 
classes  of  animals  explain  the  accurate  ob- 
servations made  by  physiologists,  who  have 
established  beyond  all  doubt  the  fact,  that 
animals  give  out  pure  nitrogen  through  the 
skin  and  lungs,  in  variable  quantity.  This 
fact  is  so  much  the  more  important,  as  it 
furnishes  the  most  decisive  proof,  that  the 
nitrogen  of  the  air  is  applied  to  no  use  in 
the  animal  economy. 

The  fact  that  nitrogen  is  given  out  by  the 
skin  and  lungs,  is  explained  by  the  property 
which  animal  membranes  possess  of  allow- 
ing all  gases  to  permeate  them,  a  property 
which  can  be  shown  to  exist  by  the  most 
simple  experiments.  A  bladder,  filled  with 
carbonic  acid,  nitrogen,  or  hydrogen  gas,  if 
tightly  closed  and  suspended  in  the  air,  loses 
in  24  hours  the  whole  of  the  enclosed  gas ; 
by  a  kind  of  exchange,  it  passes  outwards 
into  the  atmosphere,  while  its  place  is  occu- 
pied by  atmospherical  air.  A  portion  of 
intestine,  a  stomach,  or  a  piece  of  skin  or 
membrane,  acts  precisely  as  the  bladder,  if 
filled  with  any  gas.  This  permeability  to 
gases  is  a  mechanical  property,  common  to 
all  animal  tissues ;  and  it  is  found  in  the 
same  degree  in  the  living  as  in  the  dead 
tissue. 

It  is  known  that  in  cases  of  wounds  of 
the  lungs  a  peculiar  condition  is  produced, 
in  which,  by  the  act  of  inspiration,  not  only 
oxygen  but  atmospherical  air,  with  its  whole 
amount  (£ths)  Of  nitrogen,  penetrates  into 
the  cells  of  the  lungs.  This  air  is  carried 
by  the  circulation  to  every  part  of  the  body, 
so  that  every  part  is  inflated  or  puffed  up 
with  the  air,  as  with  water  in  dropsy.  This 
state  ceases,  without  pain,  as  soon  as  the 
entrance  of  the  air  through  the  wound  is 


stopped.  There  can  be  no  doubt  that  the 
oxygen  of  the  air,  thus  accumulated  in  the 
cellular  tissue,  enters  into  combination,  while 
its  nitrogen  is  expired  through  the  skin  and 
lungs. 

Moreover,  it  is  well  known  that  in  many 
graminivorous  animals,  when  the  digestive 
organs  have  been  overloaded  with  fresh  juicy 
vegetables,  these  substances  undergo  in  the 
stomach  the  same  decomposition  as  they 
would  at  the  same  temperature  out  of  the 
body.  They  pass  into  fermentation  and 
putrefaction,  whereby  so  great  a  quantity 
of  carbonic  acid  gas  and  of  inflammable 
gas  is  generated,  that  these  organs  are  enor- 
mously distended,  sometimes  even  to  burst- 
ing. From  the  structure  of  their  stomach  or 
stomachs,  these  gases  cannot  escape  through 
the  oesophagus  ;  but  in  the  course  of  a  few 
hours,  the  distended  body  of  the  animal  be- 
comes less  swollen,  and  at  the  end  of  twenty- 
four  hours  no  trace  of  the  gases  is  left.  (25.) 

Finally,  if  we  consider  the  fatal  accidents 
which  so  frequently  occur  in  wine  countries 
from  the  drinking  of  what  is  called  feather- 
white  wine  (der  fedetfaveisse  Wein,^  we  can 
no  longer  doubt  that  gases  of  every  kind, 
whether  soluble  or  insoluble  in  water,  pos- 
sess the  property  of  permeating  animal  tis- 
sues, as  water  penetrates  unsized  paper. 
This  poisonous  wine  is  wine  still  in  a  state 
of  fermentation,  which  is  increased  by  the 
heat  of  the  stomach.  The  carbonic  acid  gas 
which  is  disengaged  penetrates  through  the 
parietes  of  the  stomach,  through  the  dia- 
phragm, and  through  all  the  intervening 
membranes,  into  the  air-cells  of  the  lungs, 
out  of  which  it  displaces  the  atmospherical 
air.  The  patient  dies  with  all  the  symptoms 
of  asphyxia  caused  by  an  irrespirable  gas ; 
and  the  surest  proof  of  the  presence  of  the 
carbonic  acid  in  the  lungs  is  the  fact,  that  the 
inhalation  of  ammonia  (which  combines 
with  it)  is  recognized  as  the  best  antidote 
against  this  kind  of  poisoning. 

The  carbonic  acid  of  effervescing  wines 
and  of  soda-water,  when  taken  into  the  sto- 
mach, or  of  water  saturated  with  this  gas,  ad- 
ministered in  the  form  of  enema,  is  given  out 
again  through  the  skin  and  lungs  ;  and  this 
is  equally  true  of  the  nitrogen  which  is  in- 
troduced into  the  stomach  with  the  food  in 
the  saliva. 

No  doubt  a  part  of  these  gases  may  enter 
the  venous  circulation  through  the  absorb- 
ent and  lymphatic  vessels,  and  thus  reach 
the  lungs,  where  they  are  exhaled ;  but  the 
presence  of  membranes  offers  not  the  slight- 
est obstacle  to  their  passing  directly  into  the 
cavity  of  the  chest.  It  is,  in  fact,'  difficult 
to  suppose  that  the  absorbents  and  lympha- 
tics have  any  peculiar  tendency  to  absorb 
air,  nitrogen  or  hydrogen,  and  convey  these 
gases  into  the  circulation,  since  the  intestines, 
the  stomach,  and  all  spaces  in  the  body  not 
filled  with  solid  or  liquid  matters,  contain 
gases,  which  only  quit  their  position  when 
their  volume  exceeds  a  certain  point,  and 
which,  consequently,  are  not  absorbed. 


40 


ANIMAL   CHEMISTRY. 


More  especially  in  reference,  to  nitrogen,  we 
roust  suppose  that  it  is  removed  from  the 
stomach  by  some  more  direct  means,  and 
not  by  the  blood,  which  fluid  must  already, 
in  passing  through  the  lungs,  have  become 
saturated  with  that  gas,  that  is,  must  have 
absorbed  a  quantity  of  it,  proportioned  to  its 
s :  Ivent  power,  like  any  other  liquid.  By  the 
respiratory  motions,  all  the  gases  which  rill 
the  otherwise  empty  spaces  of  the  body  are 
urged  towards  the  chest ;  for  by  the  motion 
of  the  diaphragm  and  the  expansion  of  the 
chest  a  partial  vacuum  is  produced,  in  con- 
sequence of  which  air  is  forced  into  the 
chest  from  all  sides  by  the  atmospheric  pres- 
sure. The  equilibrum  is,  no  doubt,  restored, 
for  the  most  part,  through  the  windpipe,  but 
all  the  gases  in  the  body  must,  nevertheless, 
receive  an  impulse  towards  the  chest.  In 
birds  and  tortoises  these  arrangements  are 
reversed.  If  we  assume  that  a  man  intro- 
duces into  the  stomach  in  each  minute  only 
|th  of  a  cubic  inch  of  air  with  the  saliva, 
this  makes  in  eighteen  hours  135  cubic 
inches ;  and  if  £th  be  Deducted  as  oxygen, 
there  will  still  remain  108  cubic  inches  of 
nitrogen,  which  occupy  the  space  of  3  Ibs. 
of  water.  Now  whatever  may  be  the  actual 
amount  of  the  nitrogen-  thus  swallowed,  it 
is  certain  that  the  whole  of  it  is  given  out 
again  by  the  mouth,  nose,  and  skin  ;  and 
when  we  consider  the  very  large  quantity 
of  nitrogen  found  in  the  intestines  of  exe- 
cuted criminals  by  Magendie,  as  well  as  the 
entire  absence  oif  oxygen  in  these  organs, 
(26,)  we  must  assume  that  air,  and  conse- 
quently nitrogen,  enters  the  stomach  by  re- 
sorptipn  through  the  skin,  and  is  afterwards 
exhaled  by  the  lungs. 

When  animals  are  made  to  respire  in  gases 
containing  no  nitrogen,  more  of  that  gas 
is  exhaled,  because  in  this  case  the  nitrogen 
within  the  body  acts  towards  the  external 
space  as  if  the  latter  were  a  vacuum.  (See 
Graham  "On  the  Diffusion  of  Gases.") 

The  differences  in  the  amount  of  expired 
nitrogen  in  different  classes  of  animals  are 
thus  easily  explained ;  the  herbivora  swal- 
low with  the  saliva  more  air  than  the  carni- 
vora;  they  expire  more  nitrogen  than  the 
latter, — less  when  fasting  than  immediately 
after  taking  food. 

13.  In  the  same  way  as  muscular  fibre, 
when  separated  from  the  body,  communi- 
cates the  state  of  decomposition  existing  in 
its  elements  to  the  peroxide  of  hydrogen,  so 
a  certain  product,  arising  by  means  of  the 
vital  process,  and  in  consequence  of  the 
transposition  of  the  elements  of  parts  of  the 
stomach  and  of  the  other  digestive  organs, 
while  its  own  metamorphosis  is  accom- 
plished in  the  stomach,  acts  on  the  food. 
The  insoluble  matters  become  soluble — they 
are  digested. 

It  is  certainly  remarkable,  that  hard-boiled 
white  of  egg,  or  fibrine,  when  rendered  so- 
luble by  certain  liquids,  by  organic  acids, 
or  weak  alkaline  solutions,  retain  all  their 
properties  except  the  solid  form  (cohesion) 


without  the  slightest  change.  Their  ele- 
mentary molecules,  without  doubt  assume 
a  new  arrangement ;  they  do  not,  however, 
separate  into  two  or  more  groups,  but  re- 
main united  together. 

The  very  same  thing  occurs  in  the  di- 
gestive process  ;  in  the  normal  state,  the  food 
only  undergoes  a  change  in  its  state  of  co- 
hesion, becoming  fluid  without  any  other 
change  of  properties. 

The  greatest  obstacle  to  forming  a  clear 
conception  of  the  nature  of  the  digestive 
process,  which  is  here  reckoned  among 
those  chemical  metamorphoses  which  have 
been  called  fermentation  and  putrefaction, 
consists  in  our' involuntary  recollection  of 
the  phenomena  which  accompany  the  fer- 
mentation of  sugar  and  of  animal  sub- 
stances, (putrefaction,)  which  phenomena 
we  naturally  associate  with  any  similar 
change;  but  there  are  numbe&less  cases  in 
which  a  complete  chemical  metamorphosis 
of  the  elements  of  a  compound  occurs  with- 
out the  smallest  disengagement  of  gas,  and 
it  is  chiefly  these  which  must  be  borne  in 
mind,  if  we  would  acquire  a  clear  and  accu- 
rate idea  of  the  chemical  notion  or  concep- 
tion of  the  digestive  process. 

All  substances  which  can  arrest  the  phe- 
nomena of  fermentation  and  putrefaction  in 
liquids,  also  arrest  digestion  when  taken  into 
the  stomach.  The  action  of  the  empyreu- 
matic  matters  in  coffee  and  tobacco  smoke, 
of  creosote,  of  mercurials,  &c.,  &c.,  is  on 
this  account  worthy  of  peculiar  attention 
with  reference  to  dietetics. 

The  identity  in  composition  of  the  chief 
constituents  of  blood  and  of  the  nilrogenized 
constituents  of  vegetable  food  has  certainly 
furnished,  in  an  unexpected  manner,  an 
explanation  of  the  fact  that  putrefying  hlood, 
white  of  egg,  flesh,  and  cheese  produce  the 
same  effects  in  a  solution  of  sugar  as  yeast 
or  ferment;  that  sugar,  in  contact  with  these 
substances,  according  to  the  particular  stage 
of  decomposition  in  which  the  putrefying 
matters  may  be,  yields,  at  one  time,  alcohol 
and  carbonic  acid  ;  at  another,  lactic  acid, 
mannite,  and  mucilage.  The  explanation 
is  simply  this,  that  ferment,  or  yeast,  is 
nothing  but  vegetable  fibrine,  albumen,  or 
caseine  in  a  state  of  decomposition,  these 
substances  having  the  same  composition 
with  the  constituents  of  flesh,  blood,  or 
cheese.  The  putrefaction  of  these  animal 
matters  is  a  process  identical  with  the  meta- 
morphosis of  the  vegetable  matters  identical 
with  them  ;  it  is  a  separation  or  splitting  up 
into  new  and  less  complex  compounds. 
And  if  we  consider  the  transformation  of 
the  elements  of  the  animal  body  (the  waste 
of  matter  in  animals)  as  a  chemical  process 
which  goes  on  under  the  influence  of  the 
vital  force,  then  the  putrefaction  of  animal 
matters  out  of  the  body  is  a  division  into 
simpler  compounds,  in  which  the  vital 
force  takes  no  share.  The  -action  in  both 
cases  is  the  same,  only  the  products  differ. 
The  practice  of  medicine  has  furnished  the 


ir5 


COMPOSITION    OF  FIBRINE    &c. 


41 


most  beautiful  and  interesting  observations 
on  the  action  of  empyreumatic  substances, 
such  as  wood,  vinegar,  creosote,  &c.,  on 
malignant  wounds  and  ulcers.  In  such 
morbid  phenomena  two  actions  are  going 
on  together;  one  metamorphosis,  which 
strives  to  complete  itself  under  the  influence 
of  the  vital  force,  and  another,  independent 
of  that  force.  The  latter  is  a  chemical  pro- 
cess, which  is  entirely  suppressed  or  arrested 
by  empyreumatic  substances ;  and  this  effect 
is  precisely  opposed  to  the  poisonous  influ- 
ence exercised  on  the  organism  by  putrefy- 
ing blood  when  introduced  into  a  fresh 
wound. 

14.  The  formula  C  H*  N6OM*  is  that 
which  most  accurately  expresses  the  com- 
position of  proteine,  or  the  relative  propor- 
tions of  the  organic  elements  in  the  blood, 
as  ascertained  t»y  analysis.  Albumen,  fibrine, 
and  caseine  contain  proteine;  caseine  con- 
tains, besides,  sulphur,  but  no  phosphorus  ; 
albumen  and  fibrine  contain  both  these  sub- 
stances chemically  combined — the  former 
more  sulphur  than  the  latter.  We  cannot 
directly  ascertain  in  what  form  the  phos- 
phorus exists.  But  we  have  decided  proof 
that  the  sulphur  cannot  be  in  the  oxidized 
state.  All  these  substances,  when  heated 
with  a  moderately  strong  solution  of  potash, 
yield  the  sulphur  which  we  find  in  the  solu- 
tion as  sulphuret  of  potassium ;  and  on  the 
addition  of  an  acid  it  is  given  off  as  sul- 
phuretted hydrogen.  When  pure  fibrine  or 
ordinary  albumen  is  dissolved  in  a  weak 
solution  of  potash,  and  acetate  of  lead  is 
added  to  the  solution,  in  such  proportion 
that  the  whole  of  the  oxide  of  lead  remains 
dissolved  in  the  potash,  the  mixture,  if 
heated  to  the  boiling  point,  becomes  black 
like  ink,  and  sulphuret  of  lead  is  deposited 
as  a  fine  black  powder. 

It  is  extremely  .probable,  that  by  the 
action  of  the  alkali  the  sulphur  is  removed 
as  sulphuretted  hydrogen,  the  phosphorus 
as  phosphoric  or  phosphorus  acid.  Since, 
in  mis  case,  sulphur  and  phosphorus  are 
eliminated  on  the  one  hand,  and  oxygen  and 
hydrogen  on  the  other,  it  might  be  con- 
cluded that  fibrine  and  albumen,  when 
analyzed  with  their  sulphur  and  phosphorus, 
would  yield  a  larger  proportion  of  oxygen 
and  hydrogen  than  is  found  in  proteine.  But 
this  cannot  be  shown  in  the  analysis;  for 
fibrine,  for  example,  has  been  found  to  con- 
tain 0'3G  per  cent,  of  sulphur.  Assuming, 
then,  that  this  sulphur  is  eliminated  by  the 
alKali  in  combination  with  hydrogen,  pro- 
teine would  yield  0-0225  per  cent,  less  hy- 
drogen than  fibrine;  instead  of  the  mean 
amount  of  7-062  per  cent,  of  hydrogen,  the 
proteine  should  yield  7*04  per  cent.  In  like 
manner,  by  the  elimination  of  the  phos- 
phorus in  combination  with  oxygen,  the 
amount  of  oxygen  in  fibrine  would  be  re- 
duced from  22-715— 22-00  per  cent,  to  22- 5 — 

*  For  the  method  of  converting  this  and  other 
formula  into  propoitions  per  cent.,  see  Appendix. 


21 '8  per  cent,  in  proteine.  But  the  limits  of 
error  in  our  analyses  are,  on  an  average, 
beyond  y^th  per  cent,  in  the  hydrogen,  and 
beyond  T*5ths  per  cent,  in  the  oxygen  ;  while 
in  the  supposed  case  the  difference  in  the 
hydrogen  would  not  be  greater  than  ^th 
per  cent. 

Finally,  if  we  reflect,  thai  the  elimination 
of  oxygen  and  hydrogen  with  the  sulphur 
and  phosphorus  does  not  exclude  the  addi- 
tion of  the  elements  of  water,  and  if  we  as- 
sume that  fibrine  and  albumen,  in  passing 
into  proteine,  do  combine  with  a  certain 
quantity  of  water,  an  occurrence  which  is 
highly  probable,  we  shall  see  that  there  is 
no  probability  that  the  ultimate  analysis  of 
these  compounds  shall  ever  enable  us  to  de- 
cide such  questions,  or  to  fix  the  chemical 
view  of  the  relation  of  proteine  to  albumen, 
fibrine,  or  caseine,  farther  than  has  been 
done  above. 

Some  have  endeavoured  to  prove  the  ex- 
istence of  unoxidized  phosphorus  in  albumen 
and  fibrine  from  the  formation  of  sulphuret 
of  potassium  when  they  are  acted  on  by 
potash,  supposing  the  oxygen  of  the  potash 
to  have  formed  phosphoric  acid  with  the 
phosphorus;  but  caseine,  which  contains 
no  phosphorus,  yields  sulphuret  of  potas- 
sium, just  like  the  other  substances;  and 
here  its  formation  cannot  be  accounted  for, 
unless  we  admit  the  previous  production  of 
sulphuretted  hydrogen.  In  the  mere  boiling 
of  flesh,  for  the  purpose  of  making  soup, 
sulphuretted  hydrogen,  as  Chevreul  has 
shown,  is  disengaged. 

Moreover,  the  proportion  of  sulphur,  foi 
the  same  amount  of  phosphorus,  is  not  the 
same  in  fibrine  and  albumen,  from  which  no 
other  conclusion  can  be  drawn,  but  that  the 
formation  of  sulphuret  of  potassium  has  no 
relation  to  the  presence  of  phosphorus.  Sul- 
phuret of  potassium  is  formed  from  caseine, 
which  is  not  supposed  to  contain  any  un- 
combined  phosphorus;  and  it  is  formed, 
also,  from  albumen,  which  contains  only 
half  as  much  phosphorus  as  fibrine. 

Every  attempt  to  give  the  true  absolute 
amount  of  the  atoms  in  fibrine  and  albumen 
in  a  rational  formula,  in  which  the  sulphur 
and  phosphorus  are  taken,  not  in  fractions, 
but  in  entire  equivalents,  must  be  fruitless, 
because  we  are  absolutely  unable  to  deter- 
mine with  perfect  accuracy  the  exceedingly 
minute  quantities  of  sulphur  and  phosphorus 
in  such  compounds ;  and  because  a  variation 
in  the  sulphur  or  phosphorus,  smaller  in 
extent  than  the  usual  limit  of  errors  of  ob- 
servation, will  affect  the  number  of  atoms 
of  carbon,  hydrogen,  or  oxygen  to  the  extpnt 
of  10  atoms  or  more. 

We  must  be  careful  not  to  deceive  our- 
selves in  our  expectations  of  what  chemical 
analysis  can  do.  We  know,  with  certainty, 
that  the  numbers  representing  the  relative 
proportions  of  the  organic  elements  are  the 
same  in  albumen  and  fibrine,  and  hence  we 
conclude  that  they  have  the  same  composi- 
tion. This  conclusion  is  not  affected  by  the 

D* 


/v  .\  1  M  A  L   C  1:1  E  M  I  IS  T  li  1 . 


fact,  that  we  do  not  know  the  absolute  num- 
ber of  the  atoms  of  their  elements,  which 
have  united  to  form  the  compound  atom. 

15.  A  formula  for  proteine  is  nothing 
more  than  the  nearest  and  most  exact  ex- 
pression in  equivalents,  of  Ine  result  of  the 
best  analyses;  it  is  a  fact  estabhsned  so  far, 
free  from  doubt,  and  this  alone  is,  for  the 
present,  valuable  to  us. 

If  we  reflect,  that  from  the  albumen  and 
fibrine  of  the  body  all  the  other  tissues  are 
derived,  it  is  perfectly  clear  that  this  can 
only  occur  in  two  ways.  Either  certain 
elements  have  been  added  to,  or  removed 
irorn,  their  constituent  parts. 

If  we  now,  for  example,  lock  for  an  ana- 
lytical expression  of  the  composition  of  cel- 
lular tissue,  of  the  tissues  yielding  gelatine, 
or  tendons,  of  hair,  of  horn,  &c.,  in  which 
the  number  of  atoms  of  carbon  is  made  in- 
variably the  same  as  in  albumen  and  fibrine, 
we  can  then  see  at  the  first  glance,  in  what 
way  the  proportion  of  the  other  elements 
has  been  altered;  but  this  includes  all  that 
physiology  requires  in  order  to  obtain  an  in- 
sight into  the  true  nature  of  the  formative 
and  nutritive  processes  in  the  animal  body. 

From  the  researches  of  Mulder  and  Sche- 
rer  we  obtain  the  following  empirical  formulae. 

Composition  of  organic  tissues. 
Albumen   .        .        . 
Fibrine      .        .         . 
Caseine      .        .         . 
Gelatinous  tissues,  >  _ 

Chondrine .        .         .  C48N6H40O«° 
Hair,  horn.         . 
Arterial  membrane 

The  composition  of  these  formulae  shows, 
that  when  proteine  passes  into  chondrine, 
(the  substance  of  the  cartilages  of  the  ribs,) 
the  elements  of  water,  with  oxygen,  have 
been  added  to  it;  while  in  the  formation  of 
the  serous  membranes,  nitrogen  also  has 
entered  into  combination. 

If  we  represent  the  formula  of  proteine, 
C'WH^O14  by  Pr,  then  nitrogen,  hydrogen, 
and  oxygen  have  been  added  to  it  in  the 
form  of  known  compounds,  and  in  the  fol- 
lowing proportions,  in  forming  the  gelatinous 
tissues,  hair,  horn,  arterial  membrane,  &c. 
Proteine.  Ammonia.  Water.  Oxygen. 
Fibrine,  Albumen    Rr 
Arterial  Membrane  Pr    .         +2HO. 
Chondrine  .        .     Pr    .         +4HO.4-2O. 
Hair,  horn  .        .     Pr+  NH8      .     .  +  3O. 
Gelatinous  tissues  2Pr-f3NH3-f  HO.+7O. 

17.  From  this  general  statement  it  ap- 
pears that  all  the  tissues  of  the  body  contain, 
for  the  same  amount  of  carbon,  more  oxygen 
than  the  constituents  of  blood.  During  their 
formation,  oxygen,  either  from  the  atmo- 
sphere or  from  the  elements  of  water,  has 
been  added  to  the  elements  of  prot^ne.  In 


*  The  quantities  of  sulphur  and  phosphorus 
here  expressed  by  S  and  P  are  not  equivalents, 
but  only  give  the  relative  proportions  of  these  two 
elements  to  each  other,  as  found  by  analysis. 


hair  and  gelatinous  membrane  we  observe, 
farther,  an  excess  of  nitrogen  and  hydrogen, 
and  that  in  the  proportions  to  form  ammonia. 

Chemists  are  not  yet  agreed  on  the  ques- 
tion, in  what  manner  the  elements  of  sul- 
phate of  potash  are  arranged;  it  would 
|  therefore  be  going  too  far,  were  they  to 
I  pronounce  arterial  membrane  a  hydrate  of 
proleine,  chondrine  a  hydrated  oxide  of  pro- 
teine, and  hair  and  membranes  compounds 
of  ammonia  with  oxides  of  proteine. 

The  above  formula?  express  with  preci- 
sion the  differences  of  composition  in  the 
chief  constituents  of  the  animal  body;  they 
show,  that  for  the  same  amount  of  carbon 
the  proportion  of  the  other  elements  varies, 
and  how  much  more  oxygen  or  nitrogen 
one  compound  contains  than  another. 

18.  By  means  of  these  formulae  we  can 
trace  the  production  of  the  different  com- 
pounds from  the  constituents  of  blood ;  but 
the  explanation  of  their  production  may 
take  two  forms,  and  we  have  to  decide 
which  of  these  comes  nearest  to  the  truth. 

For  the  same  amount  of  carbon,  mem- 
branes and  the  tissues  which  yield  gelatine 
contain  more  nitrogen,  oxygen,  and  hydro- 
gen than  proteine.  It  is  conceivable  that 
they  are  formed  from  albumen  by  the  addi- 
tion of  oxygen,  of  the  elements  of  water, 
and  of  those  of  ammonia,  accompanied  by 
the  separation  of  sulphur  and  phosphorus ; 
at  all  events,  their  composition  is  entirely 
different  from  that  of  the  chief  constituents 
of  blood. 

The  action  of  caustic  alkalies  on  the  tis- 
sues yielding  gelatine  shows  distinctly  that 
they  no  longer  contain  proteine ;  that  sub- 
stance cannot  in  any  way  be  obtained  from 
them;  and  all  the  products  formed  by  the 
action  of  alkalies  on  them  differ  entirely 
from  those  produced  by  the  compounds  o'i 
proteine  in  the  same  circumstances.  Whe- 
ther proteine  exist,  ready  formed,  in  fibrine. 
albumen,  and  caseine,  or  not,  it  is  certain 
that  their  elements,  under  the  influence  of 
the  alkali,  arrange  themselves  so  as  to  forru 
proteine;  but  this  property  is  wanting  in  the 
elements  of  the  tissues  which  yield  gelatine 

The  other,  and  perhaps  the  more  proba- 
ble explanation  of  the  production  of  these 
tissues  from  proteine,  is  that  which  makes  it 
dependent  on  a  separation  of  carbon. 

If  we  assume  the  nitrogen  of  proteine  to 
remain  enure  in  the  gelatinous  tissue,  then 
the  composition  of  the  latter  calculated  on  b 
equivalents  of  nitrogen,  would  be  repre- 
sented by  the  formula,  C^N^^O14.  This 
formula  approaches  most  closely  to  the 
analysis  of  Scherer,  although  it  is  not  an 
exact  expression  of  his  results.  A  formula 
corresponding  more  perfectly  to  the  analysis, 
is  C'WH^O12;  or  calculated  accordin  to 
Mulder's  analysis, 


*  The  formula  C^NsH^O20,  adopted  by  Mu! 
der,  gives,  when  reduced  to  100  parts,  too  little 
nitrogen  f>  be  considered  an  exact  expression  of 
his  analyses. 


METAMORPHOSIS   OF   TISSUES. 


43 


According  to  the  first  formula,  carbon  and 

f  hydrogen  have  been  separated;  according 
to  the  two  last,  a  certain  proportion  of  all 
the  elements  has  been  removed 
19.  We  must  admit,  as  the  most  im- 
portant result  of  the  study  of  the  composi- 
tion of  gelatinous  tissue,  and  as  a  point  un- 
deniably established,  that,  although  formed 
front  compounds  of  proteine,  it  no  longer 
belongs  to  the  series  of  the  compounds  of 
proteine.  Its  chemical  characters  and  com- 
position justify  this  conclusion. 

No  fact  is  as  yet  opposed  to  the  law,  de- 
duced from  observation,  that  nature  has  ex- 
clusive-ly  destined  compounds  of  proteine 
for  the  production  of  blood. 

No  substance  analogous  to  the  tissues 
yielding  gelatine  is  found  in  vegetables. 
The  gelatinous  substance  is  not  a  compound 
of  proteine ;  it  contains  no  sulphur,  no  phos- 
phorus, and  it  contains  more  nitrogen  or  less 
carbon  than  proteine.  The  compounds  of 
proteine,  under  the  influence  of  the  vital 
energy  of  the  organs  which  form  the  blood, 
assume  a  new  form,  but  are  not  altered 
in  composition;  while  these  organs,  as  far  as 
our  experience  reaches,  do  not  possess  the 
power  of  producing  compounds  of  proteine, 
by  virtue  of  any  influence,  out  of  substances 
which  contain  no  proteine.  Animals  which 
are  fed  exclusively  with  gelatine,  the  most 
highly  nitrogenized  element  of  the  food  of 
carnivora,  died  with  the  symptoms  of  starva- 
tion ;  in  short,  the  gelatinous  tissues  are 
incapable  of  conversion  into  blood. 

But  there  is  no  doubt  that  these  tissues 
are  formed  from  the  constituents  of  the 
blood ;  and  we  can  hardly  avoid  entertain- 
ing the  supposition,  that  the  fibrine  of  venous 
blood,  in  becoming  arterial  fibrine,  passes 
through  the  first  stage  of  conversion  into 
gelatinous  tissue.  We  cannot,  with  much 
probability,  ascribe  to  membranes  and  ten- 
dons the  power  of  farming  themselves  out 
of  matters  brought  by  the  blood ;  for  how 
could  any  matter  become  a  portion  of  the 
cellular  tissue,  for  example,  by  virtue  of  a 
force  which  has  as  yet  no  organ  ?  An  al- 
ready existing  cell  may  possess  the  power  of 
reproducing  or  of  multiplying  itself,  but  in 
both  cases  the  presence  of  a  substance  iden- 
tical in  composition  with  cellular  tissue  is 
essential.  Such  matters  are  formed  in  the 
organism,  and  nothing  can  be  better  fitted 
for  thpir  production  than  the  substance  of 
•he  cells  and  membranes  which  exist  in  ani- 
mal food,  and  become  soluble  in  the  stomach 
during  digestion,  or  which  are  taken  by  man 
in  a  soluble  form. 

20.  In  the  following  pages  I  offer  to  the 
reader  an  attempt  to  develope  analytically 
the  principal  metamorphoses  which  occur 
in  the  animal  body;  and,  to  preclude  all 
misapprehension,  I  do  this  with  a  distinct 
protest  against  all  conclusions  and  deduc- 
tions which  may  now  or  at  any  subsequent 
period  be  derived  from  it  in  opposition  to 
the  views  developed  in  the  preceding  part 
01  this  work,  with  which  it  has  no  manner 


of  connexion.  The  results  here  to  be  de- 
scribed have  surprised  me  no  less  than  they 
will  others,  and  have  excited  in  my  mind 
I  the  same  doubts  as  others  will  conceive; 
|  but  they  are  not  the  creations  of  fancy,  and 
I  give  them  because  I  entertain  the  deep 
conviction  that  the  method  which  has  led  to 
them  is  the  only  one  by  which  we  can  hope 
j  to  acquire  insight  into  the  nature  of  the 
organic  processes. 

The  numberless  qualitative  investigations 
of  animal  matters  which  are  made  are 
equally  worthless  for  physiology  and  for 
chemistry,  so  long  as  they  are  not  instituted 
with  a  well  defined  object,  or  to  answer  a 
question  clearly  put. 

If  we  take  the  letters  of  a  sentence  which 
we  wish  to  decipher,  and  place  them  in  a 
line,  we  advance  not  a  step  towards  the  dis- 
covery of  their  meaning.  To  resolve  an 
enigma,  we  must  have  a  perfectly  clear  con- 
ception of  the  problem.  There  are  many 
ways  to  the  highest  pinnacle  of  a  mountain ; 
but  those  only  can  hope  to  reach  it  who 
keep  the  summit  constantly  in  view.  All 
our  labour  and  all  our  efforts,  if  we  strive  to 
attain  it  through  a  morass,  only  serve  to 
cover  us  more  completely  with  mud;  our 
progress  is  impeded  by  difficulties  of  our  own 
creation,  and  at  last  even  the  greatest  strength 
must  give  way  when  so  absurdly  wasted. 

21.  If  it  be  true  that  all  parts  of  the  body 
are  formed  and  developed  from  the  blood  or 
the  constituents  of  the  blood,  that  the  exist- 
ing organs  at  every  moment  of  life  are  trans- 
formed into  new  compounds  under  the  in- 
fluence of  the  oxygen   introduced   in   the 
blood,  then  the  animal  secretions  must  of 
necessity  contain  the  products  of  the  meta- 
morphosis of  the  tissues. 

22.  If  it  be  further  true,  that  the  urine 
contains  those  products  of  metamorphosis 
which  contain  the  most  nitrogen,  and  the 
bile  those  which  are  richest  in  carbon,  from 
all  the  tissues  which  in  the  vital  process  have 
been    transformed   into   unorganized   com 
pounds,  it  is  clear  that  the  elements  of  the 
bile  and  of  the  urine  sdded  together,  must 
be  equal  in  the  relative  proportion  of  these 
elements  to  the  composition  of  the  blood. 

23.  The  organs  are  formed  from  the  blood, 
and  contain  the  elements  of  the  blood ;  they 
become  transformed  into  new  compounds, 
with  the  addition  only  of  oxygen  and  of  . 
water.     Hence  the  relative   proportion   of; 
carbon  and  nitrogen  must  be  the  same  as  in 
the  blood. 

If  theri  we  subtract  from  the  composition 
of  blood  the  elements  of  the  urine,  then  the 
remainder,  deducting  the  oxygen  and  water 
which  have  been  added,  must  give  the  com- 
position of  the  bile. 

Or  if  from  the  elements  of  the  blood,  we 
subtract  the  elements  of  the  bile,  the  remain- 
der must  give  the  composition  of  urate  of 
ammonia,  or  of  urea  and  carbonic  acid. 

It  will  surely  appear  remarkable  that  this 
manner  of  viewing  the  subject  has  led  to  the 
,  true  formula  of  bile,  or,  to  speak  more  accu- 


44 


ANIMAL   CHEMISTRY. 


rately,  to  the  most  correct  empirical  expres- 
sion of  its  composition;  and  has  furnished 
the  key  to  its  metamorphoses,  under  the  in- 
fluence of  acids  and  alkalies,  which  had  pre- 
viously been  sought  for  in  vain. 

24.  When  fresh  drawn  blood  is  made  to 
trickle  over  a  plate  of  silver,  heated  to  140°, 
it  dries  to  a  red,  varnish-like  matter,  easily 
reduced  to  powder.  Muscular  flesh,  free  from 
fat,  if  dried  first  in  a  gentle  heat,  and  then 
at  212°,  yields  a  brown,  pulverizable  mass. 

The  analyses  of  Play  fair  and  Boeck- 
mann  (28)  give  for  flesh  (fibrine,  albumen, 
cellular  tissue,  and  nerves)  and  for  blood,  as 
the  most  exact  expression  of  their  numerical 
results,  one  and  the  same  formula,  namely, 
CWEPO15.  This  may  be  called  the  em- 
pirical formula  of  blood. 

25.  The  chief  constituent  of  bile,  accord- 
ing to  the  researches  of  Dema^ay,  is  a 
compound,  analogous  to  soaps,  of  soia  with 
a  peculiar  substance,  which  has  been  named 
choleic  acid.     This  acid  is  obtained  in  com- 
bination with  oxide  of  lead,  when  bile,  puri- 
fied by  means  of  alcohol  from  all  matters 
insoluble  in  that  menstruum,  is  mixed  with 
acetate  of  lead. 

Choleic  acid  is  resolved,  by  the  action  of 
muriatic  acid,  into  ammonia,  taurine,  and  a 
new  acid,  choloidic  acid,  which  contains  no 
nitrogen. 

When  boiled  with  caustic  potash,  choleic 
acid  is  resolved  into  carbonic  acid,  ammonia, 
and  another  new  acid,  cholic  acid  (distinct 
from  the  cholic  acid  of  Gmelin.) 

Now  it  is  clear  that  the  true  formula  of 
choleic  acid  must  include  the  analytical  ex- 
pression of  these  modes  of  decomposition ; 
in  other  words,  that  it  must  enable  us  to 
show  that  the  composition  of  the  products 
derived  from  it  is  related  in  a  clear  and 
simple  manner,  to  the  composition  of  the 
acid  itself.  This  is  the  only  satisfactory  test 
of  a  formula ;  and  the  analytical  expression 
thus  obtained  loses  nothing  of  its  truth  or 
value,  if  it  should  appear,  as  the  researches 
of  Berzelius  seem  to  show,  that  choleic 
and  choloidic  acids  are  mixtures  of  different 
compounds  ;  for  the  relative  proportions  of 
the  elements  cannot  in  any  way  be  altered 
by  this  circumstance. 

26.  In  order  to  develope  the  metamor- 
phoses wnich  choleic  acid  suffers  under  the 
influence  of  acids  and  alkalies,  the  following 
formula  alone  can  be  adopted  as  the  empiri- 
cal expression  of  the  results  of  its  analysis, 
Formula  of  choleic  acid:  CTN^HTO22.  (29) 

I  repeat,  that  this  formula  may  express 
the  composition  of  one,  or  of  two  or  more 
compounds ;  no  matter  of  how  many  com- 
pounds the  so-called  choleic  a^id  may  be 
made  up,  the  above  formula  represents  the 
relative  proportions  of  all  their  elements 
taken  together. 

If  now  we  subtract  from  the  elements  of 
choleic  acid,  the  products  formed  by  the 
action  of  muriatic  acid,  namely,  ammonia 
and  taurine,  we  obtain  the  empirical  formula 
of  choloidic  acid.  Thus  from  the 


Formula  of  choleic  acid 

Substract — 

1  at.  taurine  C4NH7O10  ? 
1  eq.  ammonia  NH3      > 


=  C4N2Hl°010 


There  remains  the  for- 
mula   of    choloidic 

acid —C72 

27.  Again,  if  from  the  formula  of  chojeic 
acid  we  subtract  the  elements  of  urea  and  2 
atoms  of  water  (=2  eq.  carbonic  acid  and  2 
eq.  ammonia,)  there  will  remain  the  formula 
and  composition  of  cholic  acid.  Thus : 
from  the 

Formula  of  choleic  acid 

Substract — 

2  eq.  car.  acid  =C2  O4  ? 
2  eq.  ammonia  =  N2H6  } 


=C2N2  H6  O4 


Remains   the  formula 
of  cholic  acid  =C74    H60O18(31.) 

When  we  consider  the  very  close  coinci- 
dence between  these  formulas  and  the  actual 
results  of  analysis  (see  Appendix,  29,  30, 
31,)  it  is  scarcely  possible  to  doubt  that  the 
formula  above  adopted  for  choleic  acid  ex- 
presses, as  accurately  as  is  to  be  expected 
in  the  analysis  of  such  compounds,  the  rela- 
tive proportion  of  its  elements,  no  matter  in 
how  many  different  forms  they  may  be 
united  to  produce  that  acid. 

28.  Let  us  now  add  the  half  of  the  num- 
bers which  represent  the  formula  of  choleic 
acid,  to  the  elements  of  the  urine  of  ser- 
pents— that  is,  to  neutral  urate  of  ammonia, 
as  follows : 

\  the  formula  of  choleic  acid  = 

Add  to  this — 

1  eq,  uric  acid  =C10N4H4O6  ? 
leq.  ammonia  =    NH3       > 

The  sum  is =C48N6H40O17 

29.  But  this  last  formula  expresses  the 
composition  of  blood,  with  the  addition  of  1 
eq.  oxygen,  and  1  eq.  water. 

Formula  of  blood  ....  C48N6H39O18 
1  eq.  water  =HO  >  jjj  Q2 
1  eq.  oxygen  =  O  $  ~~ '  


The  sum  is    ...-.= 

30.  If,  moreover,  we  add  to  the  elements 
of  proteine  those  of  3  eq.  water,  we  obtain, 
with  the  exception  1  eq.  hydrogen,  exactlv 
the  same  formula. 

Formula  of  proteine     .     .      =C48N6H36O14 
Add  3  eq.  of  water    .     .    .    =  H3O» 


The  sum  is    ..... 

differing  only  by  1  eq.  of  hydrogen  from 
the  formula  above  obtained  by  adding  to 
gether  choleic  acid  and  urate  of  ammonia. 

31.  If,  then,  we  consider  cholerc  acid  and 
urate  of  ammonia  the  products  of  the  trans- 
formation of  muscular  fibre,  since  no  other 
tissue  in  the  body  contains  proteine  (for 
albumen  passes  into  tissues,  without  our 
being  able  to  say,  that  in  the  vital  process 
it  is  directly  resolved  into  choleic  acid,  and 
urate  of  ammonia,)  there  exist  in  fibrine, 
with  the  addition  of  the  elements  of  water, 
all  the  elements  essential  to  this  metamor 


URIC    AC1U   AJ\L>    UR&A. 


45 


phosis ;  and,  except  the  sulphur  and  phos- 
phorus, both  of  whiph  are  probably  oxidized, 
no  element  is  separated. 

This  form  of  metamorphosis  is  applicable 
to  the  vital  transformations  in  the  lower 
classes  of  amphibia,  and  perhaps  in  worms 
and  insects.  In  the  higher  classes  of  ani- 
mals the  uric  acid  disappears  in  the  urine, 
and  is  replaced  by  urea. 

The  disappearance  of  uric  acid  and  the  pro- 
duction of  urea  plainly  stand  in  a  very  close 
relation  to  the  amount  of  oxygen  absorbed  in 
respiration,  and  to  the  quantity  of  water  con- 
sumed by  different  animals  in  a  given  time. 

When  uric  acid  is  subjected  to  the  action 
of  oxygen,  it  is  first  resolved,  as  is  well 
known,  into  alloxan  and  urea.  (32.)  A  new 
supply  of  oxygen  acting  on  the  alloxan 
causes  it  to  resolve  itself  either  into  oxalic 
acid  and  urea,  into  oxaluric  and  parabanic 
acids,  (33,)  or  into  carbonic  acid  and  urea. 

32.  In  the  so-called  mulberry  calculi  we 
find  oxalate  of  lime,  in  other  calculi  urate 
of  ammonia,  and  always  in  persons,  in 
whom,  from  want  of  exercise  and  labour, 
or  from  other  causes,  the  supply  of  oxygen 
has  been  diminished.  Calculi  containing 
uric  acid  or  oxalic  acid  are  never  found  in 
phthisical  patients ;  and  it  is  a  common 
occurrence  in  France,  among  patients  suf- 
fering from  calculous  complaints,  that  when 
they  go  to  the  country^  where  they  take 
more  exercise,  the  compounds  of  uric  acid, 
which  were  deposited  in  the  bladder  during 
their  residence  in  town,  are  succeeded  by 
oxalates  (mulberry  calculus,)  in  consequence 
of  the  increased  supply  of  oxygen.  With 
a  still  greater  supply  of  oxygen  they  would 
have  yielded,  in  healthy  subjects,  only  the 
last  product  of  the  oxidation  of  uric  acid, 
namely,  carbonic  acid  and  urea. 

An  erroneous  interpretation  of  the  unde- 
niable fact  that  all  substances  incapable  of 
farther  use  in  the  organism  are  separated  by 
the  kidneys  and  expelled  from  the  body  in 
the  urine,  altered  or  unaltered,  has  led  prac- 
tical medical  men  to  the  idea,  that  the  food, 
and  especially  nitrogenized  food,  may  have 
a  direct  influence  on  the  formation  of  urinary 
calculi.  There  are  no  reasons  which  sup- 
port this  opinion,  while  those  opposed  to  it 
are  innumerable.  It  is  possible  that  there 
may  be  taken,  in  the  food,  a  number  of  mat- 
teis  changed  by  the  culinary  art,  which,  as 
oeing  no  longer  adapted  to  the  formation  of 
blood,  are  expelled  in  the  urine,  more  or 
less  altered  by  the  respiratory  process.  But 
roasting  and  boiling  alter  in  no  way  the 
composition  of  animal  food.  (34.) 

Boiled  and  roasted  flesh  is  converted  at 
once  into  blood ;  while  the  uric  acid  and 
urea  are  derived  from  the  metamorphosed 


tissues.  The  quantity  of  these  products 
increases  with  the  rapidity  of  transformation 
in  a  given  time,  but  bears  no  proportion  to 
the  amount  of  food  taken  in  the  same  period. 
In  a  starving  man  who  is  in  any  way  com- 
pelled to  undergo  severe  and  continued  ex- 
ertion, more  urea  is  secreted  than  in  the 
most  highly  fed  individual,  if  in  a  state  of 
rest.  In  fevers  and  during  rapid  emaciation 
the  urine  contains  more  urea  than  in  a  state 
of  health.  (Prout.) 

33.  In  the  same  way,  therefore,  as  the 
hippuric  acid,  present  m  the  urine  of  the 
horse  when  at  rest,  is  converted  into  ben- 
zoate  of  ammonia  and  carbonic  acid  as  soon 
as  the  animal  is  compelled  to  labour,  so  the 
uric  acid  disappears  in  the  urine  of  man, 
when  he  receives,  through  the  skin  and 
lungs,  a  quantity  of  oxygen  sufficient  to 
oxidize  the  products  of  the  transformation 
of  the  tissues.  The  use  of  wine  and  fat, 
which  are  only  so  far  altered  in  the  organ- 
ism that  they  combine  with  oxygen,  has  a 
marked  influence  on  the  formation  of  uric 
acid.  The  urine,  after  fat  food  has  been 
taken,  is  turbid,  and  deposits  minute  crystals 
of  uric  acid.  (Prout.)  The  same  thing  is 
observed  after  the  use  of  wines  in  which 
the  alkali  necessary  to  retain  the  uric  acid 
in  solution  is  wanting,  but  never  from  the 
use  of  Rhenish  wines,  which  contain  so 
much  tartar. 

In  animals  which  drink  much  water,  by 
means  of  which  the  sparingly  soluble  uric 
acid  is  kept  dissolved,  so  that  the  inspired 
oxygen  can  act  on  it,  no  uric  acid  is  found 
in  the  urine,  but  only  urea.  In  birds,  which 
seldom  drink,  uric  acid  predominates. 

If  to  one  atom  of  uric  acid  we  add  6  atoms 
of  oxygen  and  4  atoms  of  water,  it  resolves 
itself  into  urea  and  carbonic  acid: 
1  atom  uric  acid 
4  atoms  water     > 
6  atoms  oxygen  $" 


.H4O10 


f  2  atoms  urea 

I  6  atoms  carbonic  acid 


C4N4H80* 
C6         O" 

C10N4H8O16 

34.  The  urine  of  the  herbivora  contains  no 
uric  acid,  but  ammonia,  urea,  and  hippuric 
or  benzoic  acid.  By  the  addition  of  9  atoms 
of  oxygen  to  the  empirical  formula  of  their 
blood  multiplied  by  5,  we  obtain  the  ele- 
ments of  6  at.  of  hippuric  acid,  9  at.  of 
urea,  3  at.  of  choleic  acid,  3  at.  of  water, 
and  3  at.  of  ammonia;  or,  if  we  suppose 
45  atoms  of  oxygen  to  be  added  to  the  blood 
during  its  metamorphoses,  then  we  obtain 
6  at.  of  benzoic  acid,  13£  at.  of  urea,  3  at 
of  choleic  acid,  15  at.  of  carbonic  acid,  and 
12  at.  of  water. 


5(C48N6H39Ols)-f  O9 


("6  atoms  hippuric  acid,  6 
9  atoms  urea  ...  9 
6  atoms  choleic  acid  .  3 
3  atoms  ammonia  .  3 
3  atoms  water  .  3 


C18N  H8  O5  )  =  C!08N6  H^O30 

Q2  N2H4  Q2  )  =  C18  N^H^O18 

H38O")  =  C114N3  H^O33     . 
N  H3       )  =        N3  H9 
H3  O3  )  =  H3  O3 


46 


ANIMAL    CHEMISTRY. 


Or— 


6  atoms  benzoic  acid,  6 
27 12  atoms  urea  .  .  27 

3  atoms  choleic  acid  3 
15  atoms  carbonic  acid  15 
12  atoms  water  .  12 


15)  -f  O45  =  C240N30H195O120 


The  sum  is 


C27  Ns 

C114N3  H99O38 
C15  O30 

H12012 

^195^20 


35.  Lastly,  let  us  follow  the  metamor- 
phosis of  the  tissues  in  the  fcetal  calf,  con- 
sidering the  proteine  furnished  in  the  blood 
of  the  mother  as  the  substance  which  under- 
goes or  has  undergone  a  transformation;  it 


will  appear  that  2  at.  of  proteme  withou* 
the  addition  of  oxygen  or  any  other  foreign 
element,  except  2  at.  of  water,  contain  the 
elements  of  6  at.  of  allantoine  and  1  at.  of 
choloidic  acid  (meconium?) 


2  atoms  proteine  =  2  fG*N«H*QH)  +  2  atoms  water  =  2HO  =  C8«NaH*O11 
6  atoms  allantoine,    6  (C4N2H3O3)  =  CWH^O18 
1  atom  choloidic  acid  =  C72      H56O12 


f 

_.    3 

^ 


36.  But  the  elements  of  the  six  atoms  of  I  exactly  to  the  elements  of  2  at.  ol  uric  acid, 
allantoine  in  the  last  equation  correspond  |  2  at.  of  urea,  and  2  at.  of  water. 

'2  atoms  uric  acid  C20N8H8O12 
6  atoms  of  allantoine  =  C^N^H^O18 < 

atoms  water  H2O2 


The  relations  of  allantoine,  which  is  found 
in  the  urine  of  the  foetal  calf,  to  the  nitro- 
genized constituents  of  the  urine  in  animals 
which  respire,  are,  as  may  be  seen  by  com- 
paring the  above  formula?,  such  as  cannot 
be  overlooked  or  doubted.  Allantoine  con- 
tains the  elements  of  uric  acid  and  urea — 
that  is,  of  the  nitrogenized  products  of  the 


transformation  of  the  compounds  of  proteme. 
37.  Further,  if  to  the  formula  of  proteine, 
multiplied  by  3,  we  add  the  elements  of  4 
at.  of  water,  and  if  we  deduct  from  the  sum 
of  all  the  elements  half  of  the  elements  of 
choloidic  acid,  there  remains  a  formula 
which  expresses  very  nearly  the  composi- 
tion of  gelatine.  From 


3  (C-WH^O14)  -f  4  HO  .  .  . 
Subtract  £  atom  choloidic  acid 
There  remain 


C144N18H112O46 
;  C36       H28  O6 

C108N18H84O40(35) 


38.  Subtracting  from  this  formula  of  gela- 
tine the  elements  of  2  at.  of  proteine,  there 
remain  the  elements  of  urea,  uric  acid,  and 


water,  or  of  3  at.  of  allantoine  and  3  at.  of 
water.     Thus — 


-l 


Formula  of  gelatine  (Mulder) 

Subtract  2  atoms,  proteine     .     C96  N12H72O28 

There  remain    .     . 
1  atom  uric  acid  C10N4H4O6  } 
1  atom  urea     .    C2N2H4O2  £  = 
4  atoms  water  H4O4  3 


C12  N6  H12O12 

3  atoms  allantoine  CKN6H9O9 
3  atoms  water     ,  H3O3 


39.  The  numerical  proportions  calculated 
from  the  above  formula  differ  from  those 
actually  obtained  in  the  analyses  of  Mulder 
and  Sherer  in  this,  that  the  latter  indicate 
somewhat  less  of  nitrogen  in  gelatine;  but 
if  we  assume  the  formula  to  be  correct,  it 
then  appears,  from  the  statement  just  given, 
that  the  elements  of  two  atoms  of  proteine, 
plus  the  nitrogenized  products  of  the  trans- 
formation of  a  third  atom  of  proteine  (uric 
acid  and  urea)  and  water;  or  three  atoms 
of  proteine,  minm  the  elements  of  a  com- 
pound containing  no  nitrogen,  which  ac- 
tually occurs  as  one  of  the  products  of  the 
transformation  of  choleic  acid,  yield  in  both 
cases  a  formula  closely  approaching  to  the 
composition^ gelatinous  tissues.  We  must, 
however,  attach  to  such  formula,  and  to 
the  considerations  arising  from  them,  no 


more  importance  than  justly  belongs  to 
them.  I  would  constantly  remind  the  reader 
that  their  use  is  to  serve  as  points  of  con- 
nexion, which  may  enable  us  to  acquire 
more  accurate  views  as  to  the  production 
and  decomposition  of  those  compounds 
which  form  the  animal  tissues.  They  are 
the  first  attempts  to  discover  the  path  which 
we  must  follow  in  order  to  attain  the  object 
of  our  researches;  and  this  object,  the  goal 
we  strive  to  reach,  is,  and  must  be,  at- 
tainable. 

The  experience  of  all  those  who  have  oc- 
cupied themselves  with  researches  into  na- 
tural phenomena  leads  to  this  general  result, 
that  these  phenomena  are  caused  or  pro- 
duced, by  means  far  more  simple  than  those 
previously  supposed,  or  than  we  even  now 
i  imagine ;  and  it  is  precisely  their  simplicity 


ORIGIN   OF   THE    BILE. 


47 


which  should  most  powerfully  excite  our 
wonder  and  admiration. 

Gelatinous  tissue  is  formed  from  blood, 
from  compounds  of  proteine.  It  may  be 
produced  by  the  addition,  to  the  elements  of 
proteine,  of  allantoine  and  water,  or  of  wa- 
ter, urea,  and  uric  acid  ;  or  by  the  separation 
from  the  elements  of  proteine  of  a  com- 
pound containing  no  nitrogen.  The  solution 
of  such  problems  becomes  less  difficult, 
when  the  problem  to  be  solved,  the  question 
to  be  answered,  is  matured  and  clearly  put. 
Every  experimental  decision  of  any  such 
question  in  the  negative  forms  the  starting- 
point  of  a  new  question,  the  solution  of 
which,  when  obtained,  is  the  necessary 
consequence  of  our  having  put  the  first 
question. 

40.  In  the  foregoing   sections,  no  other 
constituent  of  the  bile,  besides  choleic  acid, 
has  been  brought  into   the  calculation ;  be- 
cause it  alone  is  known  with  certainty  to 
contain  nitrogen.     Now,  if  it  be   admitted 
that  its  nitrogen  is  derived  from  the  meta- 
morphosed tissues,  it  is  not  improbable  that 
the  carbon,  and  other  elements  which  it  con- 
tains, are  derived  from  the  same  source. 

There  cannot  be  the  smallest  doubt,  that 
in  the  carnivora,  the  constituents  of  the 
urine  and  the  bile  are  derived  from  the  trans- 
formation of  compounds  of  proteine ;  for, 
except  fat,  they  consume  no  food  but  such 
as  contains  proteine,  or  has  been  formed 
from  that  substance.  Their  food  is  identical 
with  their  blood ;  and  it  is  a  matter  of  in- 
difference which  of  the  two  we  select  as  the 
starting-point  of  the  chemical  developement 
of  the  vital  metamorphoses. 

There  can  be  no  greater  contradiction, 
with  regard  to  the  nutritive  process,  than  to 
suppose  that  the  nitrogen  of  the  food  can 
pass  into  the  urine  as  urea,  without  having 
previously  become  part  of  an  organized  tis- 
sue; for  albumen,  the  only  constituent  of 
blood,  which,  from  its  amount,  ought  to  be 
taken  into  consideration,  suffers  not  the 
slightest  change  in  passing  thro  ugh  the  liver 
or  kidneys ;  we  find  it  in  every  part  of  the 
body  with  the  same  appearance  and  the 
same  properties.  These  organs  cannot  be 
adapted  for  the  alteration  or  decomposition 
of  the  substance  from  which  all  the  other 
organs  of  the  body  are  to  be  formed. 

41.  From  the   characters   of  chyle  and 
lymph,  it   appears  with  certainty  that   the 
soluble  parts  of  the  food  or  of  the  chyme 
acquire  the  form  of  albumen.     Hard-boiled 
white  of  egg,  boiled  or   coagulated  fibrine, 
which  have  again    become  soluble    in  the 
stomach,  but  have  lost  their  coagulability  by 
the  action  of  air  or  heat,  recover  these  pro- 
perties by  degrees.     In  the  chyle,  the  acid 
reaction  of  the  chyme  has  already  passed 
into  the  weak  alkaline  reaction  of  the  blood  ; 
and  the  chyle,  when,  after  passing  through 
the  mesenteric  glands,  it  has  reached  the  tho- 
racic duet,  contains  albumen  coagulable  by 
heat ;  and,  when  left  to  itself,  deposits  fibrine. 
All  the  compounds  of  proteine,  absorbed  dur- 


|  ing  the  passage  of  the  chyme  through  the 
intestinal  canal,  take  the  form  of  albumen, 
which,  as  the  results  of  incubation  in  the 
fowl's  egg  testify,  contains  the  fundamental 
elements  of  all  organized  tissues,  with  the 
exception  of  iron,  which  is  obtained  from 
other  sources. 

Practical  medicine  has  long  ago  answered 
the  question,  what  becomes  in  man  of  the 
compounds  of  proteine  taken  in  excess, 
what  change  is  undergone  by  the  supera- 
bundant nitrogenized  food?  The  blood-ves- 
sels are  distended  with  excess  of  blood,  the 
other  vessels  with  excess  of  their  fluids,  and 
if  the  too  great  supply  of  food  be  kept  up, 
and  the  blood,  or  other  fluids  adapted  for 
forming  blood,  be  not  applied  to  their  natu- 
ral purposes,  if  the  soluble  matters  be  not 
taken  up  by  the  proper  organs,  various  gases 
are  disengaged,  as  in  processes  of  putrefac- 
faction,  the  excrements  assume  an  altered 
quality  in  colour,  smell,  &,c.  Should  the 
fluids  in  the  absorbent  and  lymphatic  ves 
sels  undergo  a  similar  decomposition,  this  is 
immediately  visible  in  the  blood,  and  the 
nutritive  process  then  assumes  new  forms. 

42.  No  one  of  all  these  appearances  should 
occur,  if  the  liver  and  kidneys  were  capable 
of  effecting  the  resolution  of  the  superabun 
dant  compounds  of  proteine  into  urea,  uric 
acid,  and  bile.     All  the  observations  which 
have  been  made  in  reference  to  the  influence, 
of  nitrogenized  food  on  the  composition  of 
the  urine  have  failed  entirely  to  demonstrate 
the  existence  of  any  direct  influence  of  the 
kind  ;  for  'he  phenomena  are  susceptible  of 
another  and  a  far  more  simple  interpretation, 
if,   along  with   the  food,  we   consider  the 
mode  of  life  and  habits  of  the   individuals 
who  have  been  the  subjects  of  investigation. 
Gravel  and  calculus  occur  in  persons  who 
use  very  little  animal  food.     Concretions  of 
uric  acid  have  never  yet  been  observed  in 
carnivorous  mammalia,  living  in  the   wild 
state,*  and  among  nations  which  live  entirely 
on  flesh,  deposits  of  uric  acid  concretions  in 
the  limbs  or  in  the  bladder  are  utterly  un- 
knoAvn. 

43.  That  which  must  be  viewed   as  an 
undeniable  truth  in  regard  to  the  origin  of 
the  bile,  or,  more  accurately  speaking,  of 
choleic  acid  in  the  carnivora,  cannot  hold  in 
regard  to  all  the  constituents  of  the  bile  se- 
creted by  the  liver  in  the  herbivora,  for  with 
the  enormous  quantity  of  bile  produced,  for 
example,  by  the  liver  of  an  ox,  it  is  abso- 
lutely impossible  to  suppose  that  all  its  car- 
bon   is    derived   from   the    metamorphosed 
tissues. 

Assuming  the  59  oz.  of  dry  bile  (from  37 
Ibs.  of  fresh  bile  secreted  by  an  ox)  to  con- 
tain the  same  per  centage  of  nitrogen  as  cho- 
leic acid,  (3'86per  cent.,)  this  would  amount 
to  nearly  2^-  oz.  of  nitrogen;  and  if  this  ni- 


*  The  occurrence  of  urate  of  ammonia  in  a  con* 
cretion  found  in  a  dog,  which  was  examined  by 
I  Lassaigne,  is  to  be  doubted,  unless  Lassaigne  ex- 
I  tracted  it  himself  from  the  bladder  of  the  animal. 


ANIMAL   CHEMISTRY. 


trogen  proceed  from  metamorphosed  tissues, 
then,  if  all  the  carbon  of  these  tissues  passed 
into  the  bile,  it  would  yield,  at  the  utmost, 
a  quantity  of  bile  corresponding  to  7*15  oz. 
of  carbon.  This  is,  however,  far  below  the 
quantity  which,  according  to  observation,  is 
secreted  in  this  class  of  animals. 

44.  Other  substances,  besides  compounds 
of  proteine,  must  inevitably  take  part  in  the 
formation  of  bile  in  the  organism  of  the 
herbivora ;  and  these  substances  can  only  be 
the  non-nitrogenized  constituents  of  their 
ibod. 

45.  The  sugar  of  bile  of  Gmelin  (picromel 
or  biline  of  Berzelius,)  which  Berzelius  con- 
siders as  the  chief  constituent  of  bile,  while 
Uema^ay  assigns  that  place  essentially  to 
choleic  acid,  burns,  when  heated  in  the  air, 
like  resin,  yields  ammoniacal  products,  and 
when  treated  with  acids,  yields  taurine  and 
the  products  of  the  decomposition  of  choleic 
acid;  when  acted  on  by  alkalies,  it  yields 
ammonia  and  cholic  acid.    At  all  events, 
the  sugar  of  bile  contains  nitrogen,  and  much 
less  oxygen  than  starch  or  sugar,  but  more 
oxygen  than  the  oily  acids.     When,  in  the 
metamorphosis  of  sugar  of  bile  or  choleic 
acid  by  alkalies,  we  cause  the  separation 
of  nitrogen,  we  obtain  a  crystallized  acid, 
very  similar  to  the  oily  acids  (cholic  acid,) 
and  capable  of  forming  with  bases  salts, 
which  have  the  general  characters  of  soaps. 
Nay,  we  may  even  consider  the  chief  con- 
b..  uents  of  the  bile,  sugar  of  bile  and  cho- 
leic acid,  as  compounds  of  oily  acids  with 
organic  oxides,  like  the  fat  oils,  and  only 
differing  from  these  in  containing  no  oxide 
of  glycerule.     Choleic  acid,  for  example, 
may  be  viewed  as  a  compound  of  choloidic 
acid  with  allantoine  and  water: 

Choloid.  acid.  Allant.    Water.  Choleic  acid. 


Or  as  a  compound  of  cholic  acid,  urea, 
and  water : 

Cholic  acid.     Urea.      Water.  Choleic  acid. 
C74H60O18+C2N2H4O2-fH2O2=»C76N2H6«O22 

46.  If,  in  point  of  fact,  as  can  hardly  be 
doubted,  the  elements  of  such  substances  as 
starch,  sugar,  &,c.,  take  part  in  the  produc- 
tion of  bile  in  the  organism  of  the  herbivora, 
there  is  nothing  opposed  to  such  a  view  in 
the  composition  of  the  chief  constituents 
of  bile,  as  far" as  our  knowledge  at  present 
extends. 

If  starch  be  the  chief  agent  in  this  pro- 
cess, it  can  happen  in  no  other  way  but 
this — that,  as  when  it  passes  into  fat,  a  cer- 
tain quantity  of  oxygen  is  separated  from 
the  elements  of  the'  starch,  which,  for  the 
same  amount  of  carbon,  (for  72  atoms,)  con- 
tains five  times  as  much  oxygen  as  choloidic 
acid. 

Without  the  separation  of  oxygen  from 
the  elements  of  starch,  it  is  impossible  to 
conceive  its  conversion  into  bile;  and  this 
separation  being  admitted,  its  conversion 
into  a  compound  intermediate  in  composition 
between  starch  and  fat  offers  no  difficulty. 

4? .  Not  to  render  these  cons  iderations  a 


mere  idle  play  with  formulae,  and  not  to 
lose  sight  of  our  chief  object,  we  observe, 
therefore,  that  the  consideration  of  the 
quantitative  proportion  of  the  bile  secreted 
in  the  herbivora  leads  to  the  following  con- 
clusions : — 

The  chief  constituents  of  the  bile  of  the 
herbivora  contain  nitrogen,  and  this  nitrogen 
is  derived  from  compounds  of  proteine. 

The  bile  of  this  class  of  animals  contains 
more  carbon  than  corresponds  to  the  quan- 
tity of  nitrogenized  food  taken,  or  to  the  por- 
tion of  tissue  that  has  undergone  metamor- 
phosis in  the  vital  process. 

A  part  of  this  carbon  must,  therefore,  be 
derived  from  the  non-nitrogenized  parts  of 
the  food  (starch,  sugar,  &,c. ;)  and  in  order 
to  be  converted  into  a  nitrogenized  consti- 
tuent of  bile,  a  part  of  the  elements  of  these 
bodies  must  necessarily  have  combined  with 
a  nitrogenized  compound  derived  from  a 
compound  of  proteine. 

In  reference  to  this  conclusion,  it  is  quite 
indifferent  whether  that  compound  of  pro- 
teine be  derived  from  the  food  or  from  the 
tissues  of  the  body. 

48.  It  has  very  lately  been  stated  by  A. 
Ure,  that  benzoic  acid,  when  administered 
internally,  appears  in  the  urine  in  the  form 
of  hippuric  acid. 

Should  this  observation  be  confirmed,*  it 
will  acquire  great  physiological  significance, 
since  it  would  plainly  prove  that  the  act  of 
transformation  of  the  tissues  in  the  animal 
iody,  under  the  influence  of  certain  matters 
taken  in  the  food,  assumes  a  new  form  with 
respect  to  the  products  which  are  its  result; 
for  hippuric  acid  contains  the  elements  of 
actate  of  urea,  with  the  addition  of  those 
of  benzoic  acid  :  » 

1  at.  urea          .        .          C2N2H4O?} 

1  at.  lactic  acid    .        .     C6    H4O4>» 

2  at.  benzoic  acid      .         C28 


2  at.  chrystallized  hippuric 
acid  —  2  (C18NH9O6) 

49.  If  we  consider  the  act  of  transforma- 
tion of  the  tissues  in  the  herbivora  as  we 
lave  done  in  the  carnivora,  then  the  blood 
of  the  former  must  yield,  as  the  last  products 
of  the  metamorphosis,  from  all  the  organs 
taken  together,  choleic  acid,  uric  acid,  and 
ammonia  (see  p.  44  ;)  and  if  we  ascribe  to  the 
uric  acid  an  action  similar  to  that  of  the 
jenzoic  acid  in  Ure's  observation — such, 
namely,  that  the  further  transformation, 
owing  to  the  presence  of  this  acid,  assumes 
another  form,  the  elements  of  the  uric  acid 
jeing  incorporated  in  the  final  products — it 
will  appear,  for  example,  that  2  at.  of  pro- 


*  The  analysis  of  the  crystals  deposited  from 
the  urine  on  the  addition  of  muriatic  acid  has  not 
been  performed.  Besides,  the  statement  of  A. 
Ure,  that  hippuric  acid,  dissolved  in  nitric  acid,  is 
reddened  by  ammonia,  is  erroneous,  and  shows 
that  the  crystals  he  obtained  must  have  contained 
uric  acid. 


SECRETIONS   AND   EXCRETIONS.  4& 

teme,  with  the  addition  of  the  elements  of  i  give  rise  to  the  production  of  hippuric  acid 
3  at.  of  uric  acid  and  2  at.  of  oxygen,  might  I  and  urea. 

2  at.  proteine,    2  (CWH^O14)  = 

3  at.  uric  acid,    3  (C10N4H4O6  )  = 

2  at.  oxygen  =  O2 


The  sum  is     ...     = 

6  at.  hippuric  acid,  6  (C18N  H8O5)  =  C108N6  H48O30 

9  at- urea     .    .     .    9  (C2N2H402)  =  C18  N18H36018 

The  sum  is  = 


50.  Finally,  if  we  bear  in  mind,  that,  in 
the  herbivora,  the  non-nitrogenized  con- 
stituents of  their  food  (starch,  &c.)  must,  as 
we  have  shown,  play  an  essential  part  in 
the  formation  of  the  bile;  that  to  their  ele- 
ments must  of  necessity  be  added  those  of 
a  nilrogenized  compound,  in  order  to  pro- 


duce  the  nitrogenized  constituents  of  the 
bile,  the  most  striking  result  of  the  combina- 
tions thus  suggested  is  this,  that  the  elements 
of  starch  added  to  those  of  hippuric  acid  are 
equal  to  the  elements  of  choleic  acid, 
a  certain  quantity  of  carbonic  acid  : 


2  at.  hippuric  acid,  2  (C18NH8  O5)  —  C36N2H16O10 
5  at.  starch  .  .  5  (C12  H10O10)  =  C60  H^O50 
2  at.  oxygen  .  .  ___  ==  _  O2 

The  sum  is     .     .     .     .     . 
2  at.  choleic  acid      2  (C^NH^O11) 
20  at.  carbonic  acid  20  (C  O2  )  =  C20 


O40 


The  sum  is 


51.  Now  since  hippuric  acid  may  be  de- 
rived, along  with  urea,  from  the  compounds 
of  proteine,  when  to  the.  elements  of  the 
latter  are  added  those  of  uric  acid  (see  p. 
49;)  since,  further,  uric  acid,  choleic  acid, 
and  ammonia  contain  the  elements  of  pro- 
teine in  a  proportion  almost  identical  with 
that  of  proteine  itself  (see  p.  44;)  it  is 
obvious  that,  if  from  5  at.  of  proteine,  with 
the  addition  of  oxygen  and  of  the  elements 
Oi"  water,  there  be  removed  the  elements  of 
choleic  acid  and  ammonia,  the  remainder 
will  represent  the  elements  of  hippuric  acid 
and  of  urea ;  and  that  if,  when  this  separa- 

5  at.  proteine  "I 
15  at.  starch      I    _ 


12  at.  water 
5  at.  oxygen  J 
In  detail 

5  at.  proteine,  5  (C^H^O14)  = 
15  at.  starch,     15  (C12    H10O10)  —  C180 
12  at\  water,      12  (  HO  )  — 

5  at.  oxygen  = 


tion  occurs,  and  during  the  further  transfor- 
mation, the  elements  of  starch  be  present 
and  enter  into  the  new  products,  we  shall 
obtain  an  additional  quantity  of  choleic  acid, 
as  well  as  a  certain  amount  of  carbonic 
acid  gas. 

That  is  to  say — that  if  the  elements  of 
proteine  and  starch,  oxygen  and  water  being 
also  present,  undergo  transformation  together 
and  mutually  affect  each  other,  we  obtain, 
as  the  product  of  this  metamorphosis,  urea, 
choleic  acid,  ammonia,  and  carbonic  acid, 
and  besides  these,  no  other  product  whatever. 

The  elements  of 

f9  at.  choleic  acid 
9  at.  urea 
3  at.  ammonia 
60  at.  carbonic  acid 


H150O150 
H12O12 
O5 


The  sum  is     .     .     .     .    =  C420N30H342O23>r 

and  — 

9  at.  choleic  acid, 
9  at.  urea,     .     . 
3  at.  ammonia, 


60  at.  carbonic  acid,  60  (C 


C^NH^O11)  = 
C*N2H4O2>  =  CWH38  O18 
N  H3     )  =       N3H9 


O2)  =  C60 


O120 


The  sum  is 


The  transformation  of  the  compounds  of 
pioteme  present  in  the  body  is  effected  by 
means  of  the  oxygen  conveyed  by  the  arte- 
rial blood,  and  if  the  elements  of  starch, 
rendered  soluble  in  the  stomach,  and  thus 
carried  to  every  part,  enter  into  the  newly 
formed  compounds,  we  have  the  chief  con- 
stituents of  the  animal  secretions  and  ex- 
cretions ;  carbonic  acid,  the  excretion  of  the 
lungs,  urea  and  carbonate  of  ammonia,  ex- 
7 


creted  by  the  kidneys,  and  choleic  acid,  se- 
creted by  the  liver. 

Nothing,  therefore,  in  the  chemical  com- 
position of  those  matters  which  may  be 
supposed  to  take  a  share  in  these  metamor- 
phoses, is  opposed  to  the  supposition  that  a 
part  of  the  carbon  of  the  non  azotized  food 
enters  into  the  composition  of  the  bile. 

52.  Pat,  in  the  animal  body,  disappears 
when  the  supply  of  oxygen  is  abundant. 
E 


ANIMAL  CHEMISTRY. 


When  that  supply  is  deficient,  choleic  acid  I  acid  is  known  to  be  the  ^hief  constituent  of 
may  be  converted  into  hippuric  acid,  litho-  the  bezoar  stones,  which  occur  in  certain 
felHc  acid,  (37)  and  water.  Lithofellic  |  herbivorous  animals  : 

2  at.  hip.  acid  C^N'H^O10 
1  at.  lith.  acid  C40    H36O8 


2  at.  choleic  acid 


O105 


10  at.  oxygen 


53.  For  the  production  of  bile  in  the 
animal  tody  a  certain  quantity  of  soda  is, 
in  all  circumstances,  necessary;  without  the 
presence  of  a  compound  of  sodium  no  bile 
can  be  formed.  In  the  absence  of  soda,  the 
metamorposis  of  the  tissues  composed  of 


14  at.  water 


C76N2H66O32 

proteine  can  yield  only  fat  and  urea.  If  we 
suppose  fat  to  be  composed  according  to 
the  empirical  formula  CnH10O,  then,  by  the 
addition  of  oxygen  and  the  elements  of 
water,  to  the  elements  of  proteine,  we  havft 
the  elements  of  fat,  urea,  and  carbonic  acid 


Proteine.  Water. 

2  (C48N6H36014)  +  12  HO  +  14  O  = 
6  at.  urea     .     .     .     = 

Fat =C66 

18  at.  carbonic  acid       ==  C18 


Oxygen. 
H 


O36 


The  composition  of  all  fats  lies  between 
the  empirical  formula?  C"H10O  and  C12H10O. 
If  we  adopt  the  latter,  then  the  elements  of 
2  at.  proteine,  with  the  addition  of  2  at. 
oxygen  and  12  at.  water,  will  yield  6  at. 
urea,  fat  (C^H^O6),  and  12  at.  carbonic  acid. 

It  is  worthy  of  observation,  in  reference 
to  the  production  of  fat,  that  the  absence  of 
common  salt  (a  compound  of  sodium  which 
furnishes  soda  to  the  animal  organism) 
is  favorable  to  the  formation  of  fat;  that  the 
fattening  of  an  animal  is  rendered  impossi- 
ble, when  we  add  to  its  food  an  excess  of 
salt,  although  short  of  the  quantity  required 
to  produce  a  purgative  effect. 

54.  As  a  kind  of  general  view  of  the 
metamorphoses  of  the  nitrogenized  animal 
secretions,  attention  may  here  be  very  pro- 
perly directed  to  the  fact,  that  the  nitrogen- 
ized products  of  the  transformation  of  the 
bile  are  identical  in  ultimate  composition 
with  the  constituents  of  the  urine,  if  to  the 
laiter  be  added  a  certain  proportion  of  the 
elements  of  water. 

1  at.  uric  acid  C:°N4H4  O6  }       , 
14  at.  water  .  .          H14OuS-=4 

* 


1  at.  uric  acid  C10N4H4  O6  1 
1  at.  urea  ...C2N2H4O2  >*  = 
22  at.  water  .  .  H^O22.) 


3  at.  taurine 
—  ">  3  at.  ammonia      N3H9 


2  at.  oxygen 


O2  _) 


1  at.  allantoine  C4N2H3O3  ? 
1  at.  water  .  .  H7O7  5  ~ 

C4N2H10O10 

1  at.  taurine      C4N  H7O10 
1  at.  ammonia      N  H3 

C4N2H100'° 

55.  In  reference  to  the  metamorphoses  ol 
uric  acid  of  the  products  of  the  transforma- 
tion of  the  bile,  it  is  not  less  significant,  and 
worthy  of  remark,  that  the  addition  of  oxy- 
gen and  the  elements  of  water  to  the  ele- 
ments of  uric  acid  may  yield  either  taurine 
and  urea,  or  taurine,  carbonic  acid,  and  am. 
monia. 

2  at.  taurine  C8N2H14O20 
1  at.  urea  .    C2N2H4O2 


C10N4H18O22 


Add  2  at.  water  H2  O2 
CioN4Hao024 


C10N4H18O22 

at.  taurine 

2  at.  carbonic  acid  C2  O4 

2  at.  ammonia  N2H6 


C10N4H20O24 

56.  Alloxan,  plus  a  certain   amount  of  I  tains  the  elements  of  super-oxalate  of  am- 
water,  is  identical  in  the  proportion  of  ele-    monia. 
ments  with  taurine;  and  finally,  taurine  con-  I 


1  at.  alloxan*  C*N2H4  O"  > 
10  at.  water  H'°O10  f 

r2  at.  oxalic  acid  C4        O6 
1  at.  taurine  C4NH7OW=^  1  at.  ammonia        NH3 

(.4  at.  water    .  .          H4O4 
C4NH7O10 


*  It  would  be  mcst  interesting  to  investigate 
the  action  of  alloxan  on  the  human  body.  Two 
or  three  drachms,  in  crystals,  had  no  injurious 
action  on  rabbita  to  which  it  was  given.  In  man, 


a  large  dose  appeared  to  act  only  on  the  kidneys. 
In  certain  diseases  of  the  liver,  alloxan  would 
very  probably  be  found  a  most  powerful  remedy 


RELATION  OF  STARCH  TO  BILE. 


51 


57.  The   comparison  of  the  amount  of 
carbon  in  the  bile  secreted  by  an  herbivorous 
animal,  with  the  quantity  of  carbon  of  its 
tissues,  or  of  the  nitrogenized  constituents 
of  its  food,  which  in  consequence  of  the 
constant  transformations  may  pass  into  bile, 
indicates,  as  we  have  just  seen,  a  great  dif- 
ference. 

The  carbon  of  the  bile  secreted  amounts, 
at  least,  to  more  than  five  times  the  quantity 
of  that  which  could  reach  the  liver  in  con- 
sequence of  the  change  of  matter  in  the 
body,  either  from  the  metamorphosed  tissues 
or  from  the  nitrogenized  constituents  of  the 
food;  and  we  may  regard  as  well  founded 
the  supposition  that  the  non-azotized  con- 
stituents of  the  food  take  a  decided  share  in 
the  production  of  bile  in  the  herbivora;  for 
neither  experience  nor  observation  contra- 
dicts this  opinion. 

58.  We  have  given,  in  the  foregoing  para- 
graphs, the  analytical  proof,  that  the  nitro- 
genized products  of  the  transformation  of 
bile,  namely,  taurine  and  ammonia,  may  be 
formed  from  all  the  constituents  of  the  urine, 
with  the  exception  of  urea  —  that  is,  from 
hippuric  acid,  uric  acid,allantoine;  and  when 
we  bear  in  mind  that,  by  the  mere  s-eparation 
of  oxygen  and  the  elements  of  water,  cho- 
loidic  acid  may  be  formed  from  starch  ;  — 

From  6  at.starch=:(C12H10O10)=C78H60O60 
Subtract  44  at.  oxygen  ?  __  H4O48 

4  at.  water 


Remains  choloidic  acid  .  .  .     =C72H56O12j 

that,  finally,  choloidic.  acid,  ammonia,  and 
taurine,  if  added  together,  contain  the  ele- 
ments of  choleic  acid  ;  — 


1  at.  choloidic  acid  —  Cn 
1  at.  taurine   .  .  .  =  C4NH7O10 
1  at.  ammonia  .  .  =       N  H3 
1  at.  choleic^cld"  —  CTWF«O2a  ;_ 
if  all  this  be  considered,  every  doubt  as  to 
the  possibility  of  these  changes  is  removed. 

59.  Chemical  analysis  and  the  study  of 
the   living  animal  body  mutually  support 
each  other;  and  both  lead  to  the  conclusion 
that  a  certain  portion  of  the  carbon  of  the  non- 
azotized  constituents  of  food  (of  starch,  &,c., 
the  elements  of  respiration)  is  secreted  by 
the  liver  in  the  form  of  bile;  and   further, 
that  the  nitrogenized  products  of  the  trans- 
formation of  tissues  in  the  herbivora  do  not, 
as  in  the  carnivora,  reach  the  kidneys  imme- 
diately or  directly,  but  that,  before  their  ex- 
pulsion from  the  body  in  the  form  of  urine, 
they  take  a  share  in  certain  other  processes, 
especially  in  the  formation  of  the  bile. 

They  are  conveyed  to  the  liver  with  the 
non-azotized  constituents  of  the  food  ;  they 
are  returned  to  the  circulation  in  the  form 
of  bile,  and  are  not  expelled  by  the  kidneys 
till  they  have  thus  served  for  the  production 
of  the  most  important  of  the  substances  em- 
ployed in  respiration. 

60.  When  the  urine  is  left  to  itself,  the 
urea  which  it  contains  is  converted  into  car- 
bonate of  ammonia;  the  elements  of  urea 


are  in  such  proportion,  that  ly  the  addition 
of  the  elements  of  water,  ail  its  carbon  is 
converted  into  carbonic  acid,  and  all  its  ni- 
trogen into  ammonia. 


1  at.  urea  C2N2H4O2   > 
H2O2  5 


2  at.  water 


2  at.  carbonic  acid  C2         O4 
2  at.  ammonia.       ,    N2H6 


C2N2H6O4 

61.  Were  we  able  directly  to  produce 
taurine  and  ammonia  out  of  uric  acid  or  al- 
lantoine,  this  might  perhaps  be  considered 
as  an  additional  proof  of  the  share  which 
has  been  ascribed  to  these  compounds  in 
the  production  of  bile ;  it  cannot,  however, 
be  viewed  as  any  objection  to  the  views 
above  developed  on  the  subject,  that,  with 
the  means  we  possess,  we  have-not  yet  suc- 
ceeded in  effecting  these  transformations  out 
of  the  body.  Such  an  objection  loses  all  its 
force,  when  we  consider  that  we  cannot 
admit,  as  proved,  the  pre-existence  of  tau- 
rine and  ammonia  in  the  bile;  nay,  that  it 
is  not  even  probable  that  these  compounds, 
which  are  only  known  to  us  as  products  of 
the  decomposition  of  the  bile,  exist  ready 
formed,  as  ingredients  of  that  fluid. 

By  the  action  of  muriatic  acid  on  bile, 
we,  in  a  manner,  force  its  elements  to  anite 
in  such  forms  as  are  no  longer  caparle  of 
change  under  the  influence  of  the  same  re- 
agent; and  when,  instead  of  the  acid,  we 
use  potash,  we  obtain  the  same  elements, 
although  ai  ranged  in  another,  and  quite  a 
different  manner.  If  taurine  were  present, 
ready  formed,  m  bile,  we  should  obtain  the 
same  products  by  the  action  of  acids  and  of 
alkalies.  This,  however,  js  contrary  to  ex- 
perience. 

Thus,  even  if  we  could  convert  allanJoine, 
or  uric  acid  and  urea,  into  taurine  and  am 
monia,  out  of  the  body,  we  should  acquire 
no  additional  insight  into  the  true  theory  of 
the  formation  of  bile,  just  because  the  pre- 
existence  of  ammonia  and  taurine  in  the 
bile  must  be  doubted,  and  because  we  have 
no  reason  to  believe  that  urea  or  allantoine, 
as  such,  are  employed  by  the  organism  in 
the  production  of  bile.  We  can  prove  that 
their  elements  serve  this  purpose,  but  we 
are  utterly  ignorant  how  these  elements 
enter  into  these  combinations,  or  what  is 
the  chemical  character  of  the  nitrogenized 
compound  which  unites  with  the  elements 
of  starch  to  form  bile,  or  rather  choleic  acid. 

62.  Choleic  acid  may  be  formed  from 
the  elements  of  starch  with  those  of  uric 
acid  and  urea,  or  of  allalitoine,  or  of  uric 
acid,  or  of  alloxan,  or  of  oxalic  acid  and 
ammonia,  or  of  hippuric  acid.  The  possi- 
bility of  its  being  produced  from  so  great  a 
variety  of  nitrogenized  compounds  is  suffi- 
cient to  show  that  all  the  nitrogenized  pro- 
ducts of  the  metamorphosis  of  the  tissues 
may  be  employed  in  the  formation  of  bile, 


52 


ANIMAL   CHEMISTRY. 


while  we  cjnnot  tell  in  what  precise  wa 
they  are  so  employed. 

By  the  action  of  caustic  alkalies  allan 
toine  may  be  resolved  into  oxalic  acid  an 
ammonia ;  the  same  products  are  obtaine( 
when  oxamide  is  acted  on  by  the  same  re 
agents.  Yet  we  cannot,  from  the  similarity 
of  the  products,  conclude  that  these  two 
compounds  have  a  similar  constitution.  In 
like  manner  the  nature  of  the  products 
formed  by  the  action  of  acids  on  choleic  acic 
does  not  entitle  us  to  draw  any  conclusior 
as  to  the  form  in  which  its  elements  are 
united  together. 

63.  If  the  problem  to  be  solved  by  or- 
ganic chemistry  be  this,  namely,  to  explain 
the  changes  which  the  food  undergoes  in  the 
animal  body  ;  then  it  is  the  business  of  this 
science  to  ascertain  what  elements  must  be 
added,  what  elements  must  be  separated,  in 
order  to  effect,  or,  in  general,  to  render  possi- 
ble, the  conversion  of  a  given  compound  into 
a  second  or  a  third  ;  but  we  cannot  expect 
from  it  the  synthetic  proof  of  the  accuracy  oi 
the  views  entertained,  because  every  thing 
in  the  organism  goes  on  under  the  influence 
of  the  vital  force,  an  immaterial  agency, 
which  the  chemist  cannot  employ  at  will. 

The  study  of  the  phenomena  which  ac- 
company the  metamorphoses  of  the  food  in 
the  organism,  the  discovery  of  the  share 
which  the  atmosphere  or  the  elements  of 
water  take  in  these  changes,  lead  at  once  to 
the  conditions  which  must  be  united  in 
order  to  the  production  of  a  secretion  or  of 
an  organized  part. 

64.  The  presence  of  free  muriatic  acid  in 
the  stomach,  and  that  of  soda  in  the  blood, 
prove  beyond  all  doubt  the  necessity  of  com- 
mon salt  for  the  organic  processes ;  but  the 
quantities  of  soda  required  by  animals  of 
different  classes,  to  support  the  vital  pro- 
cesses, are  singularly  unequal. 

If  we  suppose  that  a  given  amount  of 
blood,  considered  as  a  compound  of  soda, 
passes,  in  the  body  of  a  carnivorous  animal, 
in  consequence  of  the  change  of  matter, 
into  a  new  compound  of  soda,  namely,  the 
bile,  we  must  assume,  that  in  the  normal 
condition  of  health,  the  proportion  of  soda 
in  the  blood  is  amply  sufficient  to  form  bile 
with  the  products  of  transformation.  The 
soda  which  has  been  used  in  the  vital  pro- 
cesses, and  any  excess  of  soda  must  be  ex- 
pelled in  the  form  of  a  salt,  after  being  sepa- 
rated from  the  blood  by  the  kidneys. 

Now,  if  it  be  true,  that,  in  the  body  of 
an  herbivorous  animal,  a  much  larger 
quantity  of  bile  is  produced  than  corre- 
sponds to  the  amount  cf  blood  formed  or 
transformed  in  the  vital  processes;  if  the 
greater  part  of  the  bile,  in  this  case,  pro- 
ceeds from  the  non-azotised  constituents  of 
the  food,  then  the  soda  of  the  blood  which 
has  been  formed  into  organized  tissue  (as- 
similated or  metamorphosed)  cannot  possi- 
bly suffice  for  the  supply  of  the  daily  secre- 
tion of  bile.  The  soda,  therefore,  of  the 
bile  of  the  herbivora  must  be  supplied  di- 


rectly in  the  food;  their  organism  must  pos 
sess  the  power  of  applying  directly  to  the 
formation  of  bile  all  the  compounds  of  soda 
present  in  the  food,  and  decomposable  by 
the  organic  process.  All  the  soda  of  the 
animal  body  obviously  proceeds  from  the 
food,  but  the  food  of  the  carnivora  contains, 
at  most,  only  the  amount  of  soda  necessary 
to  the  formation  of  blood  ;  and  in  most  cases, 
among  animals  of  this  class,  we  may  as- 
sume that  only  as  much  soda  as  corresponds 
to  the  proportion  employed  to  form  the 
blood  is  expelled  in  the  urine. 

When  the  carnivora  obtain  in  their  food 
as  much  soda  as  suffices  for  the  production 
of  their  blood,  an  equal  amount  is  excreted 
in  the  urine ;  when  the  food  contains  less,  a 
part  of  that  which  would  otherwise  be  ex- 
creted is  retained  by  the  organism. 

All  these  statements  are  most  unequivo- 
cally confirmed  by  the  composition  of  the 
urine  in  these  different  classes  of  animals. 

65.  As  the  ultimate  product  of  the  changes 
of  all  compounds  of  soda  in  the  animal  body, 
we  find  in  the  urine  the  soda  in  the  form  of 
a  salt,  and  the  nitrogen  in  that  of  ammonia 
or  urea. 

The  soda  in  the  urine  of  the  carnivora  is 
bund  in  combination  with  sulphuric  and 
phosphoric  acids  j  and  along  with  the  sul- 
Dhate  and  phosphate  of  soda  we  never  fail 
;o  find  a  certain  quantity  of  a  salt  of  ammo- 
nia, either  muriate  or  phosphate  of  ammonia. 
There  can  be  no  more  decisive  evidence  in 
avour  of  the  opinion,  that  the  soda  of  their 
)ile  or  of  the  metamorphosed  constituents  of 
heir  blood  is  very  far  from  sufficing  to  neu- 
ralize  the  acids  which  are  separated,  than 
he  presence  of  ammonia  in  their  urine. 
Phis  urine,  moreover,  has  an  acid  reaction. 

In  contradistinction  to  this,  we  find,  in 

he  urine  of  the   herbivora,  soda  in    pre- 

lominating  quantity;  and  that  not  combined 

with    sulphuric  or  phosphoric   acids,   but 

with  carbonic,  benzoic,  or  hippuric  acids. 

65.  These  well  established  facts  demon- 
trate  that  the  herbivora  consume  a  far  larger 
juantity  of  soda  than  is  required  merely  for 
tie  supply  of  the  daily  consumption  of  blood, 
n  their  food  are  united-all  the  conditions  for 
tie  production  of  a  second  compound  of  soda, 
estined  for  the  support  of  the  respiratory 
irocess;  and  it  can  only  be  a  very  limited 
mowledge  of  the  vast  wisdom  displayed  in 
le  arrangements  of  organized  nature  which 
an  look  on  the  presence  of  so  much  soda 
n  the  food  and  in  the  urine  of  the  herbivora 
s  accidental. 

It  cannot  be  accidental,  that  the  life,  the 
evelopement  of  a  plant  is  dependent  on  the 
resence  of  the  alkalies  which  it  extracts 
rom  the  soil.  This  plant  serves  as  food  to 
n  extensive  class  of  animals,  and  in  these 
nimals  the  vital  process  is  again  most 
bsely  connected  with  the  presence  of  these 
Ikalies.  We  find  the  alkalies  in  the  bile, 
nd  their  presence  in  the  animal  body  is  the 
ndispensable  condition  for  the  production 
f  the  first  food  of  the  young  animal;  f( 


BILE   IN   THE   HUMAN   BODY. 


53 


without  an  abundant  supply  of  potash,  the 
production  of  milk  becomes  impossible. 

67.  All  observation  leads,  as  appears  from 
the  preceding  exposition,  to  the   opinion, 
that  certain  non-azotized  constituents  of  the 
food  of  the  herbivora  (starch,  sugar,  gum, 
&c.,)  acquire  the  form  of  a  compound  of 
soda,  which,  in  their  bodies,  serves  for  the 
same  purpose  as  that  which  we  know  cer- 
tainly   to  be   served  by  the  bile   (the  most 
highly    carbonized    product   of  the    trans- 
formation of  their  tissues)  in  the  bodies  of 
the  carnivora.     These  substances  are  em- 
ployed to  support  certain  vital  actions,  and 
are  finally  consumed  in  the  generation  of 
animal  heat,  and  in  furnishing  means  of  re- 
sistance to  the  action  of  the  atmosphere.     In 
the  carnivora,  the  rapid  transformation  of 
their  tissues  is  a  condition  of  their  existence, 
because  it  is  only  as  the  result  of  the  change 
of  matter  in  the  body  that  those  substances 
can  be  formed,  which  are  destined  to  enter 
into  combination  with  the  oxygen  of  the  air ; 
and  in  this  sense  we  may  say  that  the  non- 
azotized  constituents   of    the   food   of    the 
herbivora  impede  the  change  of  matter,  or 
retard    it,  and  render   unnecessary,   at   all 
events,  so  rapid  a  process  as  occurs   in  the 
carnivora. 

68.  The  quantity  of  azotized  matter,  pro- 
portionally so  small,  which  the  herbivora 
require  to  support  their  vital  functions,  is 
closely  connected  with  the  power  possessed 
by  the  non-azotized  parts  of  their  food  to 
act  as  means  of  supporting  the  respiratory 
process;  and  this  consideration  seems  to  ren- 
der it  not  improbable,  that  the  necessity  for 
more  complex  organs  of  digestion  in  the  her- 
bivora is  rather  owing  to  the  difficulty  of 
rendering  soluble  and  available  for  the  vital 
processes  certain   non-azotized  compounds 
(gum?    amylaceous   fibre?)   than  to    any 
thing   in   the  change  or  transformation  of 
vegetable  fibrine,  albumen  and  caseine  into 
blood  ;  since,  for  this  latter  purpose,  the  less 
complex  digestive  apparatus  of  the  carnivora 
is  amply  sufficient. 

69.  If,  in  man,  when  fed  on  a  mixed  diet, 
starch  perform  a  similar  part  to  that  which  it 
plays  in  the  body  of  the  herbivora ;  if  it  be 
assumed   that  the  elements   of  starch   are 
equally  necessary  to  the   formation    of  the 
bile  in  man  as  in  these  animals;  then  it 
follows  that  a  part  of  the  azotized  products 
of  the  transformation  of  the  tissues  in  the 
human     body,    before    they    are    expelled 
through  the  bladder,  returns  into  the  circu- 
lation from  the  liver  in  the  shape  of  bile, 
and  is  separated  by  the  kidneys  from  the 
blood,  as  the  ultimate  product  of   the  re- 
spiratory process. 

70.  When  there  is  a  deficiency  of  non- 
azotized   matter  in   the  food  of  man,  this 
form  of  the  production  of  bile  is  rendered 
impossible.     In  that    case,   the    secretions : 
must  possess  a  different  composition ;  and  f 
the  appearance  of  uric  acid  in  the  urine,  the  I 
deposition  of  uric  acid  in  the  joints  and  in  | 
the  bladder,  as  well  as  the  influence  which 


an  excess  of  animal  food  (which  must  be 
considered  equivalent  to  a  deficiency  of 
starch,  &c.,)  exercises  on  the  separation  of 
uric  acid  in  certain  individuals,  may  be  ex- 
plained on  this  principle.  If  starch,  sugar, 
&.C.,  be  deficient,  then  a  part  of  the  azotized 
compounds  formed  during  the  change  of 
matter  will  either  remain  in  the  situation 
where  they  have  been  formed,  in  which  case 
they  will  be  sent  from  the  liver  in  the  circu- 
lation, and  therefore  will  not  undergo  the 
final  changes  dependent  on  the  action  of 
oxygen ;  or  they  will  be  separated  by  the 
kidneys  in  some  form  different  from  the 
normal  one. 

71.  In  the  preceding  paragraphs  I  have 
endeavoured  to  prove  that  the  non-azotized 
constituents  of  food  exercise  a  most  decided 
influence  on  the  nature  and  quality  of  the 
animal  secretions.     Whether  this  occur  di- 
rectly ;  whether,  that  is  to  say,  their  elements 
take  an  immediate  share  in  the  act  of  trans- 
formation of  tissues  ;  or  whether  their  share 
in  that  process  be  an  indirect  one,  is  a  ques- 
tion probably  capable  of  being  resolved  by 
careful  and  cautious  experiment  and  observ- 
ation.    It  is  possible,  that  the  non-azotized 
constituents  of  food,  after  undergoing  some 
change,  are  carried  from  the  intestinal  canal 
directly  to  the  liver,  and  that  they  are  con- 
verted into  bile  in  this  organ,  where  they 
meet  with  the  products  of  the  metamor- 
phosed tissues,  and  subsequently  complete 
their  course  through  the  circulation. 

This  opinion  appears  more  probable,  when 
we  reflect  that  as  yet  no  trace  of  starch  or 
sugar  has  been  detected  in  arterial  blood, 
not  even  in  animals  which  had  been  fed  ex- 
clusively with  these  substances.  We  cannot 
ascribe  to  these  substances,  since  they  are 
wanting  in  arterial  blood,  any  share  in  the 
nutritive  process ;  and  the  occurrence  of 
sugar  in  the  urine  of  those  affected  with  dia- 
betes mellitus  (which  sugar,  according  to 
the  best  observations,  is  derived  from  the 
food)  coupled  with  its  total  absence  in  the 
blood  of  the  same  patients,  obviously  proves 
that  starch  and  sugar  are  not,  as  such,  taken 
into  the  circulation. 

72.  The  writings  of  physiologists  contain 
many  proofs  of  the  presence  of  certain  con- 
stituents of  the  bile  in  the  blood  of  man  in  a 
state  of  health,  although  their  quantity  can 
hardly  be  determined.     Indeed,  if  we  sup- 
pose 8J  Ibs.  (58,000  grs.)  of  blood  to  pass 
through  the  liver  every  minute,  and  if  from 
this  quantity  of  blood  2  drops  of  bile  (3 
grains  to  the  drop)  are  secreted,  this  would 
amount  to  Tvfath  Part  of  the  weight  of  the 
blood,  a  proportion  far  too  small  to  be  quan- 
titatively ascertained  by  analysis. 

73.  The  greater  part  of  the  bile  in  the  body 
of  the  herbivora,  and  in  that  of  man  fed  on 
mixed  food,  appears  from  the  preceding  con- 
siderations to  be  derived  from  the  elements 
of  the  non-azotized  food.     But  its  formation 
is   impossible  without  the   addition   of  an 
azotized  body,  for  the  bile  is  a  compound  of 
nitrogen.     All  varieties  of  bile  yet  examined, 


54 


ANIMAL   CHEMISTRY. 


yield,  when  subjected  to  dry  distillation,  am- 
monia and  other  nitrogenized  products. 
Taurine  and  ammonia  may  easily  be  ex- 
tracted from  ox  bile;  and  the  only  reason 
why  we  cannot  positively  prove  that  the 
same  products  may  be  obtained  from  the 
bile  of  other  animals  is  this,  that  it  is  not 
easy  to  procure,  in  the  case  of  many  of 
these  animals,  a  sufficient  quantity  of  bile 
for  the  experiment, 

Now,  whether  the  nitrogenized  compound 
which  unites  with  the  elements  of  starch  to 
form  bile  be  derived  from  the  food  or  from 
the  substance  of  the  metamorphosed  tissues, 
the  conclusion  that  its  presence  is  an  essen- 
tial condition  for  the  secretion  of  bile  cannot 
be  considered  doubtful. 

Since  the  herbivora  obtain  in  their  food 
only  such  nitrogenized  compounds  as  are 
identical  in  composition  with  the  constitu- 
ents of  their  blood,  it  is  at  all  events  clear, 
that  the  nitrogenized  compound  which  en- 
ters into  the  composition  of  bile  is  derived 
from  a  compound  of  proteine.  It  is  either 
formed  in  consequence  of  a  change  which 
the  compounds  of  proteine  in  the  food  have 
undergone,  or  it  is  produced  from  the  blood 
or  from  the  substance  of  the  tissues  by  the 
act  of  their  metamorphosis. 

74.  If  the   conclusion  be  accurate,  that 
nitrogenized   compounds,  whether  derived 
from  the  blood  or  from  the  food,  take  a  de- 
cided share  in  the  formation  of  the  secre- 
tions, and  particularly  of  the  bile,  then  it  is 
plain  that  the  organism  must  possess  the 
power  of  causing  foreign  matters,  which  are 
neither  parts  nor  constituents  of  the  organs 
in  which  vital  activity  resides,  to  serve  for 
certain  vital  processes.     All    nitrogenized 
substances  capable  of  being  rendered  solu- 
ble,  without   exception,   when   introduced 
into  the  organs  of  circulation  or  of  digestion, 
must,  if  their  composition   be  adapted  for 
such  purposes,  be  employed  by  the  organism 
in  the  same  manner  as  the  nitrogenized  pro- 
ducts which  are  formed  in  the  act  of  meta- 
morphosis of  tissues. 

We  are  acquainted  with  a  multitude  of 
substances,  which  exercise  a  most  marked 
influence  on  the  act  of  transformation  as 
well  as  on  the  nutritive  process,  while  their 
elements  take  no  share  in  the  resulting 
changes.  These  are  uniformly  substances 
the  particles  of  which  are  in  a  certain  state 
of  motion  or  decomposition,  which  state  is 
communicated  to  all  such  parts  of  the  organ- 
ism as  are  capable  of  undergoing  a  similar 
transformation. 

75.  Medicinal  and  poisonous  substances 
form  a  second  and  most  extensive  class  of 
compounds,  the  elements  of  which  are  ca- 
pable of  taking  a  direct  or  an  indirect  share 
in  the  processes  of  secretion  and  of  trans- 
formation.    These  may  be  subdivided  into 
three  great  orders ;  the  first  (which  includes 
the  metallic  poisons)  consists  of  substances 
which  enter  into  chemical  combination  with 
certain  parts  or  constituents  of  the  body, 
while  the  vital  force  is  insufficient  to  destroy 


the  compounds  thus  formed.  The  second 
division,  consisting  of  the  essential  oils, 
camphor,  empyreumatic  substances,  and 
antiseptics,  &c.,  possesses  the  property  of 
impeding  or  retarding  those  kinds  of  trans- 
formation to  which  certain  very  complex 
organic  molecules  are  liable;  transforma- 
tions which,  when  they  take  place  out  of 
the  body,  are  usually  designated  by  the 
names  of  fermentation  and  putrefaction. 

Thethird  division  of  medicinal  substances 
is  composed  of  bodies,  the  elements  of  which 
take  a  direct  share  in  the  changes  going  on 
in  the  animal  body.  When  introduced  into 
the  system,  they  augment  the  energy  of  the 
vital  activity  of  one  or  more  organs  ;  they 
excite  morbid  phenomena  in  the  healthy 
body.  All  of  them  produce  a  marked  effect 
in  a  comparatively  small  dose,  and  many 
are  poisonous  when  administered  in  larger 
quantity.  None  of  the  substances  in  this 
class  can  be  said  to  take  a  decided  share  in 
the  nutritive  process,  or  to  be  employed  by 
the  organism  in  the  production  of  blood ; 
partly,  because  their  composition  is  different 
from  that  of  blood,  and  partly,  because  the 
proportion  in  which  they  must  be  given,  to 
exert  their  influence,  is  as  nothing,  com- 
pared with  the  mass  of  the  blood. 

These  substances,  when  taken  into  the 
circulation,  alter,  as  is  commonly  said,  the 
quality  of  the  blood,  and  in  order  that  they 
may  pass  from  the  stomach  into  the  circu- 
lation with  their  entire  efficacy,  we  must 
assume  that  their  composition  is  not  affected 
by  the  organic  influence  of  tne  stomach.  If 
insoluble  when  given,  they  are  rendered 
soluble  in  that  organ,  but  they  are  not  de- 
composed; otherwise,  they  would  be  inca- 
pable of  exerting  any  influence  on  the  blood. 

76.  The  blood,  in  its  normal  state,  pos- 
sesses two  qualities  closely  related  to  each 
other,  although  we  may  conceive  one  of 
them  to  be  quite  independent  of  the  other. 

The  blood  contains,  in  the  form  of  the 
globules,  the  carriers,  as  it  were,  of  the 
oxygen  which  serves  for  the  production  of 
certain  tissues,  as  well  as  for  the  generation 
of  animal  heat.  The  globules  of  the  blood, 
by  means  of  the  property  they  possess  of 
giving  off  the  oxygen  they  have  taken  up 
in  the  lungs,  without  losing  their  peculiar 
character,  determine  generally  the  change 
of  matter  in  the  body. 

The  second  quality  of  the  blood,  namely 
the  property  which  it  possesses  of  becoming 
part  of  an  organized  tissue,  and  its  conse- 
quent adaptation  to  promote  the  formation 
and  the  growth  of  organs,  as  well  as  to  the 
reproduction  or  supply  of  waste  in  the  tis- 
sues, is  owing,  chiefly,  to  the  presence  of 
dissolved  fibrine  and  albumen.  These  two 
chief  constituents,  which  serve  for  nutri- 
tion and  reproduction  of  matter,  in  passing 
through  the  lungs  are  saturated  with  oxygen, 
or,  at  all  events,  absorb  so  much  from  the 
atmosphere  as  entirely  to  lose  the  power  of 
extracting  oxygen  from  the  other  substances 
present  in  the  blood. 


ORGANIC  REMEDIAL  AGENTS 


55 


77.  We  know  for  certain  that  the  globules 
of  the  venous  blood,  when  they  come  in  con- 
tact with  air  in  the  lungs,  change  their  co- 
lour, and  that  this  change  of  colour  is  ac- 
companied by  an  absorption  of  oxygen  ;  and 
that  all  those  constituents  of  the  blood  which 
possess  in  any  degree  the  power  of  combining 
with  oxygen,  absorb  it  in  the  lungs,  and  be- 
come saturated  with  it.    Although  in  contact 
with  these  other  compounds,  the  globules, 
when  arterialized,  retain  their  florid,  red  co- 
lour in  the  most  minute  ramifications  of  the 
arteries ;  and  we  observe  them  to  change  their 
colour,  and  to  assume  the  dark  red  colour 
which    characterizes   venous    blood,    only 
during  their  passage  through  the  capillaries. 
From  these  facts  we  must  conclude  that  the 
constituents  of  arterial  blood  are  altogether 
destitute  of  the  power  to  deprive  the  arte- 
rialized globules  of  the  oxygen  which  they 
have  absorbed  from  the  air;   and  we   can 
draw  no  other  conclusion  from  the  change 
of  colour  which  occurs  in  the   capillaries, 
than  that  the  arterialized  globules,  during 
their  passage  through  the  capillaries,  return 
to  the  condition  which  characterized  them 
in  venous   blood;  that   consequently,  they 
give  up  the  oxygen  absorbed  in  the  lungs, 
and  thus  acquire  the  power  of  combining 
with  that  element  afresh. 

78.  We  find,  therefore,  in  arterial  blood, 
albumen,  which,  like  all  the  other  consti- 
tuents of  that  fluid,  has  become  saturated 
with  cxygen  in   its   passage   through  the 
lungs,  and  oxygen  gas,  which  is  conveyed 
to  every  particle  in  the  body  in  chemical 
combination  with  the  globules  of  the  blood. 
As  far  as  our  observations  extend  (in  the 
developement  of  the  chick  during  incuba- 
tion,) all  the  conditions  seem  to   be  here 
united  which  are  necessary  to  the  formation 
of  every  kind  of  tissue ;  while  that  portion 
of  oxygen  which  is  not  consumed  in   the 
growth  or  reproduction  of  organs  combines 
with  the  substance  of  the  living  parts,  and 
produces,  by  its  union  with  their  elements, 
the  act  of  transformation  which  we  have 
called  the  change  of  matter. 

79.  It  is  obvious,  that  all  compounds,  of 
whatever   kind,  which  are  present  in   the 
capillaries,  whether  separated  there,  or  in- 
troduced by  endosmosis  or  imbibition,  if  not 
altogether  incapable  of  uniting  with  oxygen, 
must,  Avhen  in  contact  with  the  arterialized 
globules,  the  carriers  of  oxygen,  be  affected 
exactly  in  the  same  way  as  the  solids  form- 
ing  part   of   living   organs.     These   com- 
pounds, or  their  elements,  will  enter   into 
combination  with  oxygen,  and  in  this  case 
there  will  either  be  no  change  of  matter,  or 
that  change  will  exhibit   itself  in   another 
form,  yielding  products  of  a  different  kind. 

80.  The  conception,  then,  of  a  change  in 
the  two  qualities  of  the  blood  above  alluded 
to,  by  means  of  a  foreign  body  contained  in 
the  blood  or  introduced  into  the  circulation 
(a  medicinal  agent)  presupposes  two  kinds 
of  operation. 

Assuming  that  the  remedy  cannot  enter 


'  into  any  such  chemical  union  with  the  con- 
stituents of  the  blood  as  puts  an  end  to  the 
vital  activity ;  assuming,  further,  that  it  is 
not  in  a  condition  of  transformation  capable 
'.of  being  communicated  to  the  constituents 
!  of  the  blood  or  of  the  organs,  and  of  con- 
tinuing in  them ;  assuming,  lastly,  that  it  is 
incapable,  by  its  contact  with  the  living 
parts,  of  putting  a  stop  to  the  change  of 
matter,  the  transformation  of  their  elements ; 
then,  in  order  to  discover  the  modus  ope- 
rand! of  this  class  of  medicinal  agents,  no- 
thing is  left  but  to  conclude  that  their 
elements  take  a  share  in  the  formation  of 
certain  constituents  of  the  living  body,  or 
in  the  production  of  certain  secretions. 

81.  The  vital  process  of  secretion,  in  so 
far  as  it  is  related  to  the  chemical  forces,  has 
been  subjected  to  examination  in  the  preced- 
ing pages.     In  the  carnivora  we  have  rea- 
son to  believe,  that  without  the  addition  of 
any  foreign  matter  in  the  food,  the  bile  and 
the  constituents  of  the  urine  are  formed  in 
those  parts  where  the  change  of  matter  takes 
place.     In  other  classes  of  animals,  on  the 
other  hand,  we  may  suppose  that  in  the  or- 
gan of  secretion  itself,  the  secreted  fluid  is 
produced  from  certain  matters  conveyed  to 
it ;  in  the  herbivora,  for  example,  the  bile  is 
formed  from  the  elements  of  starch  along 
with  those  of  a  nitrogenized  product  of  the 
metamorphosis  of  the  tissues.     But  this  sup- 
position by  no  means  excludes  the  opinion, 
that  in  the  carnivora  the  products  of  the  me- 
tamorphosed tissues  are  resolved  into  bile, 
uric  acid,  or  urea,  only  after  reaching  the 
secreting  organ;  nor  the  opinion  that  the 
elements  of  the  non-azotized  food,  conveyed 
directly  by  the  circulation  to  every  part  of 
the  body,  where  change  of  matter  is  going 
on,  may  there  unite  with  the  elements  of  the 
metamorphosed  tissues,  to  form  the  constitu- 
ents of  the  bile  and  of  the  urine. 

82.  If  we  now  assume,  that  certain  me- 
dicinal agents  may  become  constituents  of 
secretions,  this  can  only  occur  in  two  ways. 
Either  they  enter  the  circulation,  and  take  a 
direct  share  in  the  change  of  matter  in  so 
far  as  the:r  elements  enter  into  the   compo- 
sition of 'the  new  products ;  or  they  are  con- 
veyed to  the  organs  of  secretion,  where  they 
exert  an  influence  on  the  formation  or  on 
the  quality  of  a  secretion  by  the  addition  of 
their  elements. 

In  either  case,  they  must  lose  in  the  or- 
ganism their  chemical  character ;  and  we 
know  with  sufficient  certainty,  that  this  clasg 
of  medicinal  bodies  disappear  in  the  body 
without  leaving  a  trace.  In  fact,  if  we  as- 
cribe to  them  any  effect,  they  cannot  lose 
their  peculiar  character  by  the  action  of  the 
stomach ;  their  disappearance,  therefore,  pre- 
supposes that  they  have  been  applied  to  cer- 
tain purposes,  which  cannot  be  imagined  to 
occur  without  a  change  in  their  composition. 

83.  Now,  however  limited   may  be   our 
knowledge  of  the  composition  of  the  differ- 
ent secretions,  with  the  exception  of  the 

|  bile,  this  much  is  certain,  that  all  the  secre- 


56 


ANIMAL   CHEMISTRY. 


tions  contain  nitrogen  chemically  combined. 
They  pass  into  fetid  putrefaction,  and  yield 
either  in  this  change,  or  in  the  dry  distillation, 
ammoniacal  products.  Even  the  saliva, 
when  acted  upon  by  caustic  potash,  disen- 
gages ammonia  freely. 

84.  Medicinal  or  remedial  agents  may  be 
diviued  into  two    classes,  the   nitrogenized 
and  the  non-nitrogenized.    The  nitrogenized 
vegetable     principles,   whose    composition 
differs  from  that  of  the  proper  nitrogenized 
elements  of  nutrition,  also  produced  by  a 
vegetable   organism,  are  distinguished,  be- 
yond all  others,  for  their  powerful  action  on 
fine  animal  economy. 

The  effects  of  these  substances  are  singu- 
larly varied ;  from  the  mildest  form  of  the 
action  of  aloes,  to  the  most  terrible  poison, 
strychnia,  we  observe  an  endless  variety  of 
different  action. 

With  the  exception  of  three,  all  these 
substances  produce  diseased  conditions  in 
the  healthy  organism,  and  are  poisonous  in 
certain  doses.  Most  of  them  are,  chemi- 
cally speaking,  basic  or  alkaline. 

No  remedy,  devoid  of  nitrogen,  possesses 
a  poisonous  action  in  a  similar  dose.* 

85.  The  medicinal  or  poisonous  action  of 
the  nitrogenized  vegetable  principles  has  a 
fixed  relation  to  their  composition  ;  it  can- 
not be  supposed  to  be  independent  of  the 
nitrogen  they  contain,  but  is  certainly  not  in 
direct  proportion  to  the  quantity  of  nitrogen. 

Solanine  (38,)  and  picrotoxine  (39,)  which 
contain  least  nitrogen,  are  powerful  poisons. 
Q,uinine  (40)  contains  more  nitrogen  than 
morphia  (41.)  Caffeine  (42,)  and  theobro- 
mine  the  most  highly  nitrogenized  of  all 
vegetable  principles,  are  not  poisonous. 

86.  A  nitrogenized  body,  which  exerts, 
by  means  of  its  elements,  an  influence  on 
the  formation  or  on  the  quality  of  a  secre- 
tion', must,  in  regard  to  its  chemical  charac- 
ter, be  capable  of  taking  the  same  share  as 
the  nilrogenized  products  of  the  animal  body 
do  in  the  formation  of  the  bile ;  that  is,  it 
must  play  the  same  part  as  a  product  of  the 
vital  process.     On  the  other  hand,  a  non- 
azotized  medicinal  agent,  in  so  far  as  its  ac- 
tion affects  the  secretions,  must  be   capable 
of  performing  in  the  animal  body  the  same 
part  as  that  which  we  have  ascribed  in  the 
formation  of  the  bile,  to  the  non-azotized 
elements  of  food. 

Thus,  if  we  suppose  that  the  elements  of 
hippuric  or  uric  acids  are  divided  from  the 
substance  of  the  organs  in  which  vitality 
resides  ;  that  as  products  of  the  transform- 
ation of  these  organs  they  lose  the  vital 
character,  without  losing  the  capacity  of 
undergoing  changes  under  the  influence  of 
the  inspired  oxygen,  or  of  the  apparatus  of 
secretion ;  we  can  hardly  doubt  that  similar 


*  This  consideration  or  compnraiive  view  has 
led  lately  to  a  more  accurate  investigation  of  the 
composition  of  picrotoxine,  the  poisonous  principle 
of  cocculus  indicus  ;  and  M.  Francis  has  disco 
vered  the  existence  of  nitrogen  in  it,  hitherto  over- 
looked, and  has  also  determined  its  amount. 


nitrogenized  compounds,  products  of  the 
vital  process  in  plants,  when  introduced  into 
the  animal  body,  may  be  employed  by  the 
organism  exactly  in  the  same  way  as  the 
nitrogenized  products  of  the  metamorphosis 
of  the  animal  tissues  themselves.  If  hippu- 
ric and  uric  acids,  or  any  of  their  elements, 
can  take  a  share,  for  example,  in  the  form- 
ation and  supply  of  bile,  we  must  allow  the 
same  power  to  other  analogous  nitrogenized 
compounds. 

We  shall  never,  certainly,  be  able  to  dis- 
cover how  men  Avere  led  to  the  use  of  the 
hot  infusion  of  the  leaves  of  a  certain  shrub 
(tea)  or  of  a  decoction  of  certain  roasted 
seeds  (coffee.)  Some  cause  there  must  be, 
which  would  explain  how  the  practice  has 
become  a  necessary  of  life  to  whole  nations. 
But  it  is  surely  still  more  remarkable,  that 
the  beneficial  effects  of  both  plants  on  the 
health  must  be  ascribed  to  one  and  the  same 
substance,  the  presence  of  which  in  two 
vegetables,  belonging  to  different  natural 
families,  and  the  produce  of  different  quar- 
ters of  the  globe,  could  hardly  have  presented 
itself  to  the  boldest  imagination.  Yet  recent 
researches  have  shown,  in  such  a  manner  as 
to  exclude  all  doubt,  that  caffeine,  the  pecu- 
liar principle  of  coffee,  and  theine,  that  of 
tea,  are,  in  all  respects,  identical. 

It  is  not  less  worthy  of  notice,  that  the 
American  Indian,  living  entirely  on  flesh, 
discovered  for  himself,  in  tobacco  smoke,  a 
means  of  retarding  the  change  of  matter  in 
the  tissues  of  his  body,  and  thereby  of  mak- 
ing hunger  more  endurable;  and  that  he 
cannot  withstand  the  action  of  brandy, 
which,  acting  as  an  element  of  respiration, 
puts  a  stop  to  the  change  of  matter  by  per- 
forming the  function  which  properly  belongs 
to  the  products  of  the  metamorphosed  tis- 
sues. Tea  and  coffee  were  originally  met 
with  among  nations  whose  diet  is  chiefly 
vegetable. 

87.  Without  entering  minutely  into  the 
medicinal  action  of  caffeine,  (theine,)  it  will 
surely  appear  a  most  striking  fact,  even  if 
we  were  to  deny  its  influence  on  the  pro 
cess  of  secretion,  that  this  substance,  with 
the  addition  of  oxygen  and  the  elements  of 
water,  can  yield  taurine,  the  nitrogenized 
compound  peculiar  to  bile: 

1  at.  caffeine  or  theine=C8N2H  5O2 
9  at.  water  -  =  H  9O9 
9  at.  oxygen  -  =  O9 


=2  at.  taurine  -  =  2(C4NH7O10) 
A  similar  relation  exists  in  the  case  of  the 
peculiar  principle  of  asparagus  and  of  al , 
thaea,  asparagine ;  which  also,  by  the  addi- 
tion of  oxygen  and  the  elements  of  water, 
yields  the  elements  of  taurine. 

1  at.  asparagine        =  C8N2H  8O6 
6  at.  water  =          H  6O6 

8  at.  oxygen  =  O8 

C8N2H'40To= 

=  2  at.  taurine  =(C4NH  7O10 

The  addition  of  the  elements  ol  water  and 


ACTION    OF   VEGETABLES. 


57 


of  a  certain  quantity  of  oxygen  to  the  ele- 
ments of  theobromine,  the  characteristic 
principle  of  the  cacao  bean,  (theobroma 
cacao,)  yields  the  elements  of  taurine  and 
urea,  of  taurine,  carbonic  acid,  and  ammo- 
nia, or  of  taurine  and  uric  acid  : 

1  at.  theobromine    C18N6H10O4  1 
22  at.  water        -  HTO22^ 

16  at.  oxygen  -  O16j 


C18N6H32O42 


4  at.  taurine 
1  at.  urea 


C2  N2H4  O2 


C18N6H32O42 

or — 

1  at.  theobromine    C18N6H10O4 
24  at.  water        -  H^O24 

16  at.  oxygen  O16 


4  at.  taurine 

2  at.  carbonic  acid 

2  at.  ammonia 


C16N4H28O40 

C2  O4 

N2H6 


C18N6H10O4 


O14 


C18N6H18O26 

C8  N2H14O20 
CioN4H4  Oe 


1  at.  theobromine 
8  at.  water 
14  at.  oxygen 


2  at.  taurine 
1  at.  uric  acid 


88.  To  see  how  the  action  of  caffeine,  as- 
paragine,  theobromine,  &c.5  may  be  ex- 
plained, we  must  call  to  mind  that  the  chief 
constituent  of  the  bile  contains  only  3*8  per 
cent,  of  nitrogen,  of  which  only  the  half,  or 
1-9  per  cent.,  belongs  to  the  taurine. 

Bile  contains,  in  its  natural  state,  water 
and  solid  matter,  in  the  proportion  of  90 

Earts  by  weight  of  the  former  to  10  of  the 
itter.  If  we  suppose  these  10  parts  by 
weight  of  solid  matter  to  be  choleic  acid, 
with  3-87  per  cent,  of  nitrogen,  then  100 
parts  of  fresh  bile  will  contain  0-171  parts 
of  nitrogen  in  the  shape  of  taurine.  Now 
this  quantity  is  contained  in  0'6  parts  of 
caffeine:  or  2-^ths  grains  of  caffeine  can 
give  to  an  ounce  of  bile  the  nitrogen  it  con- 
tains in  the  form  of  taurine.  If  an  infusion 
of  tea  contain  no  more  than  the  ^th  of  a 
grain  of  caffeine,  still,  if  it  contribute  in 
point  of  fact  to  the  formation  of  bile,  the 
action,  even  of  such  a  quantity,  cannot  be 
looked  upon  as  a  nullity.  Neither  can  it  be 
denied  that  in  the  case  of  an  excess  of  non- 
azotized  food  and  a  deficiency  of  motion, 
which  is  required  to  cause  the  change  of 
matter  in  the  tissues,  and  thus  to  yield  the 
nitrogenized  product  which  enters  into  the 
composition  of  the  bile ;  that  in  such  a  con- 
dition, the  health  may  be  benefited  by  the 
use  of  compounds  which  are  capable  of 
supplying  the  place  of  the  nitrogenized  pro- 
duct produced  in  the  healthy  state  of  the 
body,  and  essential  to  the  production  of  an 
important  element  of  respiration.  In  a  che- 
8 


mical  sense — and  it  is  this  alone  which  the 
preceding  remarks  are  intended  to  show — 
caffeine  or  theine,  asparagine,  and  theobro- 
mine are  in  virtue  of  their  composition  better 
adapted  to  this  purpose  than  all  other  nitro- 
genized vegetable  principles.  The  action  of 
these  substances,  in  ordinary  circumsla^-^s, 
is  not  obvious,  but  it  unquestionably  exists. 

89.  With  respect  to  the  action  of  the 
other  nitrogenized  vegetable  principles,  such 
as  quinine,  or  the  alkaloids  of  opium,  &c., 
which  manifests  itself,  not  in  the  processes 
of  secretion,  but  in  phenomena  of  another 
kind,  physiologists  and  pathologists  enter- 
tain no  doubt  that  it  is  exerted  chiefly  on 
the  brain  and  nerves.  This  action  is  com- 
monly said  to  be  dynamic — that  is,  it  acce- 
lerates, or  retards,  or  alters  in  some  way  the 
phenomena  of  motion  in  animal  life.  If  we 
reflect  that  this  action  is  exerted  by  sub- 
stances which  are  material,  tangible  and 
ponderable;  that  they  disappear  in  the  or- 
ganism ;  that  a  double  dose  acts  more  power- 
fully than  a  single  one;  that,  after  a  time,  a 
fresh  dose  must  be  given,  if  we  wish  to  pro- 
duce the  action  a  second  time ;  all  these 
considerations,  viewed  chemically,  permit 
only  one  form  of  explanation  ;  the  supposi- 
tion, namely,  that  these  compounds,  by 
means  of  their  elements,  take  a  share  i-n  the 
formation  of  new,  or  the  transformation  of 
existing  brain  and  nervous  matter. 

However  strange  the  idea  may,  at  first 
sight,  appear,  that  the  alkaloids  of  opium  or 
of  cinchona  bark,  the  elements  of  codeine, 
morphia,  quinine,  &c.,  may  be  converted 
into  constituents  of  brain  and  nervous  mat- 
ter, into  organs  of  vital  energy,  from  which 
the  organic  motions  of  the  body  derive  their 
origin ;  that  these  substances  form  a  con- 
stituent of  that  matter,  by  the  removal  of 
which  the  seat  of  intellectual  life,  of  sensa- 
tion, and  of  consciousness,  is  annihilated ; 
it  is  nevertheless  certain,  that  all  these 
forms  of  power  and  activity  are  most  closely 
dependent,  not  only  on  the  existence,  but 
also  on  a  certain  quality  of  the  substance  of 
the  brain,  spinal  marrow,  and  nerves;  inso- 
much that  all  the  manifestations  of  the  life 
or  vital  energy  of  these  modifications  of 
nervous  matter,  which  are  recognized  as  the 
phenomena  of  motion,  sensation,  or  feeling, 
assume  another  form  as  soon  as  their  com- 
position is  altered.  The  animal  organism 
has  produced  the  brain  and  nerves  out  of 
compounds  furnished  to  it  by  vegetables ; 
it  is  the  constituents  of  the  food  of  the 
animal,  which,  in  consequence  of  a  series 
of  changes,  have  assumed  the  properties  and 
the  structure  which  we  find  in  the  brain  and 
nerves. 

90.  If  it  must  be  admitted  as  an  unde- 
niable truth,  that  the  substance  of  the  brain 
and  nerves  is  produced  from  the  elements 
of  vegetable  albumen,  fibrine  and  caseine, 
either  alone,  or  with  the  aid  of  the  elements 
of  non-azotized  food  or  of  the  fat  formed 
from  the  latter,  there  is  nothing  absurd  in 
the  opinion,  that  other  constituent  of  vege 


58 


ANIMAL    CHEMISTRY. 


tables,  intermediate  in  composition  between 
the  fats  and  the  compounds  of  proteiue, 
may  be  applied  in  the  organism  to  the  same 
purpose. 

91.  According  to  the  researches  of  Fremy, 
the  chief  constituent  of  the  fat  found  in  the 
brain  is  a  compound  of  soda  with  a  peculiar 
acid,  the  cerebric  acid,  which  contains,  in 
100  parts, 

Carbon 66-7 

Hydrogen 10'6 

Nitrogen 2'3 

Phosphorus 0*9 

Oxygen 19-5 

It  is  easy  to  see  that  the  composition  of 
cerebric  acid  differs  entirely,  both  from  that 
of  ordinary  fats  and  of  the  compounds  of 
proteine.  Common  fats  contain  no  nitrogen, 
while  the  compounds  of  proteine  contain 
nearly  17  per  cent.  Leaving  the  phos- 
phorus out  of  view,  the  composition  of  this 
acid  approaches  most  nearly  to  that  of 
choleic  acid,  although  these  two  compounds 
are  quite  distinct. 

92.  Brain  and  nervous  matter  is,  at  all 
events,  formed  in  a  manner  similar  to  that 
in  which  bile  is  produced;   either  by  the 
separation  of  a  highly  nitrogenized  com- 
pound from  the  elements  of  blood,  or  by 
the  combination  of  a  nitrogenized  product 
of  the   vital  process   with   a  non-azotized 
compound  (probably,   a  fatty  body.)     All 
that  has  been  said  in  the  preceding  pages 
on  the  various  possible  ways  by  which  the 
bile  might  be  supposed  to  be  formed,  all  the 
conclusions  which   we  attained   in  regard 
to  the  co-operation  of  azotized  and   non- 
azotized  elements  of  food,  may  be  applied 
with  equal  justice  and  ecjual  probability  to 
the  formation  and  production  of  the  nervous 
substance. 

We  must  not  forget  that,  in  whatever 
light  we  may  view  the  vital  operations,  the 
production  of  nervous  matter  from  blood 
presupposes  a  change  in  the  composition 
and  qualities  of  the  constituents  of  blood. 
That  such  a  change  occurs  is  as  certain  as 
that  the  existence  of  the  nervous  matter 
cannot  be  denied.  In  this  sense,  we  must 
assume,  that  from  a  compound  of  proteine 
may  be  formed  a  first,  second,  third,  &,c., 
product  before  a  certain  number  of  its  ele- 
ments can  become  constituents  of  the  nerv- 
ous matter;  and  it  must  be  considered  as 
quite  certain,  that  a  product  of  the  vital  pro- 
cess in  a  plant,  introduced  into  the  blood, 
will,  if  its  composition  be  adapted  to  this 
purpose,  supply  the  place  of  the  first,  se- 
cond, or  third  product  of  the  alteration  of 
the  compound  of  proieine.  Indeed  it  can- 
not be  considered  merely  accidental,  that 
the  composition  of  the  most  active  remedies, 
namely,  the  vegetable  alkaloids,  cannot  be 
shown  to  be  related  to  that  of  any  consti- 
tuent of  the  body,  except  only  the  substance 
of  the  nerves  and  brain.  All  of  these  con- 
tain a  certain  quantity  of  nitrogen,  and,  in 
regard  to  their  composition,  they  are  inter- 


|  mediate  between  the  compounds  ot  proteine 
and  the  fats. 

93.  In  contradistinction  to  their  chemical 
character,  we  find  that  the  substance  of  the 
brain  exhibits  the  characters  of  an  acid.     It 
contains  far  more  oxygen  than  the  organic 
basis  or  alkaloids.     We  observe,  that  qui- 
nine an'd  cinchonine,  morphia  and  codeine, 
strychnia   and   brucia,  which   are,  respec- 
tively, so   nearly  alike   in  composition,  if 
they  do   not   produce  absolutely  the  same 
effect,   yet  resemble    each    other  in    their 
action  more  than  those  which  differ  more 
widely  in  composition.     We  find  that  their 
energy  of  action  diminishes,  as  the  amount 
of  oxygen  they  contain  increases  (as  in  the 
case  of  narcotine,)  and  that,  strictly  speak- 
ing, no  one  of  them  can  be  entirely  replaced 
by   another.     There  cannot  be  a  more  de- 
dsive  proof  of  the   nature  of  their  action 
than   this  last  fact ;  it  must  stand   in  the 
closest   relation   to   their  composition.     If 
these  compounds,  in  point  of  fact,  are  capa- 
ble of  taking  a  share  in  the  formation  or  in 
the  alteration  of  the  qualities  of  brain  and 
nervous  matter,  their  action  on  the  healthy 
as  well  as  the  deceased  organism  admits  of 
a  surprisingly  simple  explanation.     If  we 
are  not  tempted  to  deny,  that  the  chief  con- 
stituent of  soup  may  be  applied  to  a  purpose 
corresponding    to    its   composition    in    the 
human  body,  or  that  the  organic  constituent 
of  bones  may  be  so  employed  in  the  body 
of  the  dog,  although  that  substance  (gelan- 
tine  in  both  cases)  is  absolutely    incapable 
of  yielding  blood  ;  if,  therefore,  nitrogenized 
compounds,  totally  different  from  the  com- 
pounds of  proteine,  may  be  employed   for 
purposes  corresponding   to    their  composi- 
tion; we  may  thence  conclude  that  a  pro- 
duct of  vegetable   life,  also   different   from 
proteine,  but  similar  to  a  constituent  of  the 
animal  body,  may  be  employed  by  the  organ 
ism  in  the  same  way  and  for  the  same  pur- 
pose   as    the    natural    product,    originally 
formed  by  the  vital  energy  of  the    animal 
organs,  and  that  indeed  from   a  vegetable 
substance. 

The  time  is  not  long  gone  by,  when  we 
had  not  the  very  slightest  conception  of  the 
cause  of  the  various  effects  of  opium,  and 
when  the  action  of  cinchona  bark  was 
shrouded  in  incomprehensible  obscurity. 
Now  that  we  know  that  these  effects  are 
caused  by  crystallizable  compounds,  which 
differ  as  much  in  composition  as  in  their 
action  on  the  system ;  now  that  we  know 
the  substances  to  which  the  medicinal  or 
poisonous  energy  must  be  ascribed,  it  would 
argue  only  want  of  sense  to  consider  the 
action  of  these  substances  inexplicable- ;  and 
to  do  so,  as  many  have  done,  because  they 
act  in  very  minute  doses,  is  as  unreasonable 
as  it  would  be  to  judge  of  the  sharpness  of 
a  razor  by  its  weight. 

94.  It  would  serve  no  purpose  to  give 
these  considerations  a  greater  extension  at 
present.     However  hypothetical  they  may 
appear,  they  only  deserve  attention  in  so  far 


COMPOSITION  OF  NERVOUS  MATTER. 


59 


as  they  point  out  the  way  which  chemistry 
pursues,,  and  which  she  ought  not  to  quit, 
if  she  would  really  be  of  service  to  phy- 
siology and  pathology.  The  combinations 
of  the  chemist  relate  to  the  change  of  mat- 
ter, forwards  and  backwards,  to  the  con- 
version of  food  into  the  various  tissues  and 
secretions,  and  to  their  metamorphosis  into 
lifeless  compounds ;  his  investigations  ought 
to  tell  us  what  has  taken  place  and  what 
can  take  place  in  the  body.  It  is  singular 
that  we  find  medicinal  agencies  all  de- 
pendent on  certain  matters,  which  differ  in 
composition;  and  if,  by  the  introduction  of 
a  substance,  certain  abnormal  conditions  are 
rendered  normal,  it  will  be  impossible  to  reject 
the  opinion,  that  this  phenomenon  depends 
on  a  change  in  the  composition  of  the  consti- 
tuents of  the  diseased  organism,  a  change  in 
which  the  elements  of  the  remedy  take  a 
share ;  a  share  similar  to  thtvt  which  the  vege- 
table elements  of  food  have  taken  in  the  for- 
mation of  fat,  of  membranes,  of  the  saliva, 
of  the  seminal  fluid,  &,c.  Their  carbon,  hy- 
drogen, or  nitrogen,  or  whatever  else  belongs 
to  their  composition,  are  derived  from  the 
vegetable  organism ;  and,  after  all,  the  action 
and  effects  of  quinine,  morphia,  and  the 
vegetable  poisons  in  general,  are  no  hypo- 
theses. 

95.  Thus,  as  we  may  say,  in  a  certain 
eense,  of  caffeine,  or  theine,  and  asparagine, 
&c.,  as  well  as  of  the  non-azotized  elements 
of  food,  that  they  are   food  for  the  liver, 
since  they  contain  the  elements,  by  the  pre- 
sence of  which  that  organ  is  enabled  to  per- 
form  its    functions,   so   we   may    consider 
these  nitrogenized  compounds,  so  remark- 
able for  their  action  on  the  brain  and  on  the 
substance    of   the    organs   of   motion,   as 
elements  of  food  for  the  organs  as  yet  un- 
known, which  are  destined  for  the  meta- 
morphosis of  the  constituents  of  the  blood 
into  nervous  substance   and   brain.     Such 
organs  there  must  be  in  the  animal  body, 
and  if,  in  the  diseased  state,  an  abnormal 
process  of  production  or  transformation  of 
the  constituents  of  cerebral  and  nervous  mat- 
ter has  been  established ;  if,  in  the  organs  in- 
tended for  this  purpose,  the  power  of  form- 
ing that  matter  out  of  the  constituents  of 
blood,  or  the  power  of  resisting  an  abnormal 
degree  of  activity  in  its  decomposition  or 
transformation,  has  been  diminished;  then, 
in  a  chemical  sense,  there  is  no  objection  to 
the  opinion,  that  substances  of  a  composi- 
tion analogous  to  that  of  nervous  or  cerebral 

•matter,  and,  consequently,  adapted  to  form 
that  matter,  may  be  employed,  instead  of 
the  substances  produced  from  the  blood, 
either  to  furnish  the  necessary  resistance,  or 
to  restore  the  normal  condition. 

96.  Some  physiologists  and  chemists  have 


expressed  doubts  of  the  peculiar  and  dis- 
tinct character  of  cerebric  acid,  a  substance 
which,  from  its  amount  of  carbon  and 
hydrogen,  and  from  its  external  characters, 
resembles  a  nitrogenized  fatty  acid.  But  a 
nitrogenized  fat,  having  an  acid  character, 
is,  in  fact,  no  anomaly.  Hippuric  acid  is  in 
many  of  its  characters  very  similar  to  the 
fatty  acids,  but  is  essentially  distinguished 
from  them  by  containing  nitrogen.  The 
organic  constituents  of  bile  resemble  the 
acid  resins  in  physical  characters,  and  yet 
contain  nitrogen.  The  organic  alkalies  are 
intermediate  in  their  physical  characters  be- 
tween the  fats  and  resins,  and  they  all  con- 
lain  nitrogen.  A  nitrogenized  fatty  acid  is 
as  little  improbable  as  the  existence  of  a 
nitrogenized  resin  with  the  characters  of  a 
base. 

97.  An  accurate  investigation  would  pro- 
bably discover  differences  in  the  composition 
of  the  brain,  spinal  marrow  and  nerves. 
According  to  the  observations  of  Valentin, 
the  quality  of  the  cerebral  and  nervous  sub- 
stance is  very  rapidly  altered  from  the  period 
of  death,  and  very  uncommon  precautions 
would  be  required  for  the  separation  of 
foreign  matters  not  properly  belonging  to 
the  substance  of  the  spinal  marrow  or  brain. 
But,  however  difficult  it  may  appear,  the 
investigation  seems  yet  to  be  practicable. 
We  know,  in  the  meantime,  that  all  expe- 
rience is  against  the  notion  of  a  large 
amount  of  carbon  and  hydrogen  in  the  sub- 
stance of  the  brain.  The  absence  of  nitro- 
gen as  an  element  of  the  cerebral  and 
nervous  matter,  appears,  at  all  events,  im- 
probable. This  substance,  moreover,  can- 
not be  classed  with  ordinary  fats,  because 
we  find  the  cerebric  acid  combined  with 
soda,  whereas,  all  fats  are  compounds  of 
fatty  acids  with  oxide  of  glycerule.  In  re- 
gard to  the  phosphorus  of  the  brain,  we  can 
only  guess  as  to  the  form  in  which  the  phos- 
phorus exists.  "Walchner  observed  recently 
that  bubbles  of  spontaneously  inflammable 
phosphuretted  hydrogen  were  disengaged 
from  the  trough  of  a  spring  in  Carlsruhe, 
on  the  bottom  of  which  fish  had  putrefied ; 
and  gases  containing  phosphorus  have  also 
been  observed  among  the  products  of  the 
putrefaction  of  the  brain.* 


*  The  curator  of  the  museum  at  Geneva  gave 
to  M.  Leroyer,.  apothecary,  a  large  quantity  of 
spirit  of  wine,  which  had  been  used  for  the  pre- 
servation cf  fishes,  and  which  he  undertook  to 
purify.  He  distilled  from  it  a  mixture  of  chloride  of 
calcium  and  quicklime,  and  evaporated  the  residue 
in  the  air,  over  a  fire.  As  soon  as  the  mass  had 
acquired  a  certain  consistence,  and  a  higher  tem- 
perature, a  prodigious  quantity  of  spontaneously 
inflammable  phosphoretted  hydrogen  was  dia- 
engaged.  (Du.nas.  V.  267.) 


60 


ANIMAL   CHEMISTRY. 


PART  III. 


THE  PHENOMENA  OF  MOTION  IN  THE  ANIMAL  ORGANISM. 


I.  IT  might  appear  an  unprofitable  task  to 
add  one  more  to  the  innumerable  forms 
under  which  the  human  intellect  has  viewed 
the  nature  and  essence  of  that  peculiar  cause 
which  must  be  considered  as  the  ultimate 
source  of  the  phenomena  which  characterize 
vegetable  and  animal  life,  were  it  not  that 
certain  conceptions  present  themselves  as 
necessary,  deductions  from  the  views  on  this 
subject  developed  in  the  introduction  to  the 
first  part  of  this  work.  The  following  pages 
will  be  devoted  to  a  more  detailed  examina- 
tion of  these  deductions.  It  must  be  ad- 
mitted here,  that  all  these  conclusions  will 
lose  their  force  and  significance,  if  it  can  be 
proved  that  the  cause  of  vital  activity  has 
in  its  manifestations  nothing  in  common  with 
other  known  causes  which  produce  motion 
or  change  of  form  and  structure  in  matter. 

But  a  comparison  of  its  peculiarities  with 
the  modus  operand i  of  these  other  causes, 
cannot,  at  all  events,  fail  to  be  advantageous, 
inasmuch  as  the  nature  and  essence  of 
natural  phenomena  are  recognizable,  not  by 
abstraction,  but  only  by  comparative  obser- 
vations. 

If  the  vital  phenomena  be  considered  as 
manifestations  of  a  peculiar  force,  then  the 
effects  of  this  force  must  be  regulated  by 
certain  laws,  which  laws  may  be  investi- 
gated ;  and  these  laws  must  be  in  harmony 
with  the  universal  laws  of  resistance  and 
motion,  which  preserve  in  their  courses  the 
worlds  of  our  own  and  other  systems,  and 
which  also  determine  changes  of  form  and 
structure  in  material  bodies ;  altogether  in- 
dependently of  the  matter  in  which  vital 
activity  appears  to  reside  or  of  the  form  in 
which  vitality  is  manifested. 

The  vital  force  in  a  living  animal  tissue 
appears  as  a  cause  of  growth  in  the  mass, 
and  of  resistance  to  those  external  agencies 
which  tend  to  alter  the  form,  structure,  and 
composition  of  the  substance  of  the  tissue 
in  which  the  vital  energy  resides. 

This  force  further  manifests  itself  as  a 
cause  of  motion  and  of  change  in  the  form 
and  structure  of  material  substances,  by  the 
disturbance  and  abolition  of  the  state  of  rest 
in  which  those  chemical  forces  exist,  by 
which  the  elements  of  the  compounds  con- 
veyed to  the  living  tissues,  in  the  form  of 
food,  are  held  together. 

The  vital  force  causes  a  decomposition  of 
the  constituents  of  food,  and  destroys  the 
force  of -attraction  which  is  continually  ex- 
erted between  their  molecules ;  it  alters  the 
direction  of  the  chemical  forces  in  such  wise, 
that  the  elements  of  the  constituents  of  food 
arrange  themselves  in  another  form,  and 
combine  to  produce  new  compounds,  either  } 
identi  ial  in  composition  with  the  living  tis- 
sues, or  differing  from  them ;  it  further 


changes  the  direction  and  force  of  the  at 
traction  of  cohesion,  destroys  the  cohesion 
of  the  nutritious  compounds,  and  forces  the 
new  compounds  to  assume  forms  altogether 
different  from  those  which  are  the  result  of 
the  attraction  of  cohesion  when  acting  freely, 
that  is,  without  resistance. 

The  vital  force  is  also  manifested  as  a 
force  of  attraction,  inasmuch  as  the  new 
compound  produced  by  the  change  of  form 
and  structure  in  the  food,  when  it  has  a 
composition  identical  with  that  of  the  living 
tissue,  becomes  a  part  of  that  tissue. 

Those  newly-formed  compounds,  whose 
composition  differs  from  that  of  the  living 
tissue,  are  removed  from  the  situation  in 
which  they  are  formed,  and,  in  the  shape 
of  certain  secretions,  being  carried  to  other 
parts  of  the  body,  undergo  in  contact  with 
these  a  series  of  analogous  changes. 

The  vital  force  is  manifested  in  the  form 
of  resistance,  inasmuch  as  by  its  presence 
in  the  living  tissues,  their  elements  acquire 
the  power  of  withstanding  the  disturbance 
and  change  in  their  form  and  composition, 
which  external  agencies  tend  to  produce;  a 
power  which,  simply  as  chemical  com- 
pounds, they  do  not  possess. 

As  in  the  case  of  other  forces,  the  con 
ception  of  an  unequal  intensity  of  the  vita] 
force  comprehends  not  only  an  unequal 
capacity  for  growth  in  the  mass  and  an 
unequal  power  of  overcoming  chemical  re- 
sistance, but  also  an  inequality  in  the  amount 
of  that  resistance  which  the  parts  or  con- 
stituents of  the  living  tissue  oppose  to  a 
change  in  their  form  and  composition,  from 
the  action  of  new  external  active  causes  of 
change;  just  as  the  force  of  cohesion  or  of 
affinity  is  in  direct  proportion  to  the  resist- 
ance which  these  forces  oppose  to  any  ex- 
ternal cause,  mechanical  or  chemical,  tend- 
ing to  separate  the  molecules,  or  the  elements 
of  an  existing  compound. 

The  manifestations  of  the  vital  force  are 
dependent  on  a  certain  form  of  the  tissue  in 
which  it  resides,  as  well  as  on  a  fixed  com- 
position in  the  substance  of  the  living  tissue. 

The  capacity  of  growth  in  a  living  tissue 
is  determined  by  the  immediate  contact  with 
matters  adapted  to  a  certain  decomposition, 
or  the  elements  of  which  are  capable  of  be- 
coming component  parts  of  the  tissue  in 
which  vitality  resides. 

The  phenomenon  of  growth,  or  increase 
in  the  mass,  presupposes  that  the  acting 
vital  force  is  more  powerful  that  the  resis' 
ance  which  the  chemical  force  opposes  to 
the  decomposition  or  transformation  of  the 
elements  of  the  food. 

The  manifestations  of  the  vital  force  are 
dependent,  on  a  certain  temperature.  Neither 
in  a  plant  nor  in  an  animal  do  vital  phe 


MOTION    IN   THE    ANIMAi,   ORGANISM. 


01 


nomena  occur  when    the   temperature  is   once  appears  as  the  cause   of  change  oi 


lowered  to  a  certain  extent. 

The  phenomena  of  vitality  in  a  living  or- 
ganism diminish  in  intensity  when  heat  is 
abstracted,  provided  jthe  lost  heat  be  not  re- 
stored by  other  causes. 

Deprivation  of  food  soon  puts  a  stop  to 
all  manifestations  of  vitality. 

The  contact  of  the  living  tissues  with  the 
elements  of  nutrition  is  determined  in  the 
animal  body  by  a  mechanical  force  produced 
within  the  body,  which  gives  to  certain  or- 
gans the  power  of  causing  change  of  place, 
of  producing  motion,  and  of  overcoming 
mechanical  resistance. 

We  may  communicate  motion  to  a  body 
at  rest  by  means  of  a  number  of  forces,  very 
different  in  their  manifestations.  Thus,  a 
time-piece  may  be  set  in  motion  by  a  falling 
weight,  (gravitation,)  or  by  a  bent  spring 
(elasticity.)  Every  kind  of  motion  may  be 
produced  by  the  electric  or  magnetic  force, 
as  well  as  by  chemical  attraction;  while  we 
cannot  say,  as  long  as  we  only  consider  the 
manifestation  of  these  forces  in  the  pheno- 
menon or  result  produced,  which  of  these 
various  causes  of  change  of  place  has  set 
the  body  in  motion. 

In  the  animal  organism  we  are  acquainted 
with  only  one  cause  of  motion ;  and  this  is 
the  same  cause  which  determines  the  growth 
of  living  tissues,  and  gives  them  the  power 
of  resistance  to  external  agencies  ;  it  is  the 
vital  force. 

In  order  to  attain  a  clear  conception  of 
these  manifestations  of  the  vital  force,  so 
different  in  form,  we  must  bear  in  mind, 
that  every  known  force  is  recognized  by  two 
conditions  of  activity,  entirely  different  in 
the  phenomena  they  offer  to  the  attention 
of  the  observer.  time  alone,  but  to  the  pressure  multiplied 

The  force  of  gravitation  inherent  in  the   into  the  time',  which  is  called  the  momentum 
particles  of  a  stone,  gives  to  them  a  con- !  of  force. 
tinual  tendency  to  move  towards  the  centre  ' 
of  the  earth. 

This  effect  of  gravitation  becomes  inap- 


place  in  the  stone,  which  acquires  motion, 
or  falls.  Resistance  is  invariably  the  result 
of  a  force  in  action. 

According  as  the  stone  is  allowed  to  falJ 
during  a  longer  or  shorter  time,  it  acquires 
properties  which  it  had  not  while  at  rest ;  it 
acquires,  for  example,  the  power  of  over- 
coming more  feeble  or  more  powerful  obsta- 
cles, or  that  of  communicating  motion  to 
bodies  in  a  state  of  rest. 

If  it  fall  from  a  certain  height  it  makes  a 
permanent  impression  on  the  spot  on  which 
it  falls ;  if  it  fall  from  a  still  greater  height 
(during  a  longer  time)  it  perforates  the  table  ; 
its  own  motion  is  communicated  to  a  certain 
number  of  the  particles  of  the  wood  which 
now  fall  along  with  the  stone  itself.  The 
stone,  while  at  rest,  possessed  none  of  these 
properties. 

The  velocity  of  the  falling  body  is  always 
the  effect  of  the  moving  force,  and  is,  ceteris 
paribus,  proportional  to  the  force  of  gravi- 
tation. 

A  body,  falling  freely,  acquires  at  the  end 
of  one  second  a  velocity  of  30  feet.  The 
same  body,  if  falling  on  the  moon,  would 
acquire  in  one  second  only  a  velocity  of 
sWh  of  a  foot=l  inch,  because  in  the  moon 
the  intensity  of  gravitation  (the  pressure 
acting  on  the  body,  the  moving  power)  is 
360  times  smaller. 

If  the  pressure  continue  uniform,  the  ve- 
locity is  directly  proportional  to  it ;  so  that, 
for  example,  the  body  falling  360  times 
slower,  will,  after  360  seconds,  have  the 
same  velocity  as  the  other  body  after  one 
second. 

Consequently,  the  effect  is  proportional, 
not  to  the  moving  force  alone,  nor  to  the 


resses 
er  the 


In  two  equal  masses  the  velocity  exp 
the  momentum  of  force.  But  unck 
same  pressure  a  body  moves  moie  slowly 

preciable  to  the  senses  when  the  stone,  for  I  as  its  mass  is  greater ;  a  mass  twice  as  great 
example,  rests  upon  a  table,  the  particles  of  |  requires,  in  order  to  attain  in  the  same  time 

an  equal  velocity,  twice  the  pressure;  or, 
under  the  single  pressure,  it  must  continue 
in  motion  twice  as  long. 

In  order,  therefore,  to  have  an  expression 
for  the  whole  effect  produced,  we  must  mul- 
tiply the  mass  into  the  velocity.  This  pro- 
duct is  called  the  amount  of  motion. 

The  amount  of  motion  in  a  given  body 
must  in  all  cases  correspond  exactly  to  the 
momentum  of  force. 

These  two,  the  amount  of  motion  and  the 
momentum  of  force,  are  also  called  simply 
fvrce;  because  we  suppose  that  a  less  pres- 
sure acting,  for  example,  during  10  seconds, 
is  equal  to  a  pressure  ten  times  greater,  act- 
ing only  during  one  second. 

The  momentum  of  motion  in  mechanics 
signifies  the  effect  of  a  moving  force,  with- 


which  oppose  a  resistance  to  the  manifesta- 
tion of  its  gravitation.  The  force  of  gravity, 
however,  is  constantly  present,  and  mani- 
fests itself  as  a  pressure  on  the  supporting 
body ;  but  the  stone  remains  at  rest ;  it  has 
no  motion.  The  manifestation  of  gravity  in 
the  state  of  rest  we  call  its  weight. 

That  which  prevents  the  stone  from  falling 
is  a  resistance  produced  by  the  force  of  at- 
traction, by  which  the  particles  of  the  wood 
cohere  together ;  a  mass  of  water  would  not 
prevent  the  fall  of  the  stone. 

If  the  force  which  impelled  the  mass  of 
the  stone  towards  the  centre  of  the  earth 
were  greater  than  the  force  of  cohesion  in 
the  particles  of  the  wood,  the  latter  would 
be  overcome  :  it  would  be  unable  to  prevent 
the  fall  of  the  stone. 

When  we  remove  the  support,  and  with 


out  reference  to  the  time 


in  which 


(velocity)  ii 
If  one  man,  for  example, 


it  the  force  which  has  prevented  the  mani-    it  was  manifested. 

festation  of  the.  force  of  gravity,  the  latter  at ,  raises  30  Ibs.  to  a  height  of  100  feet,  and  a  se 


ANIMAL   CHEMISTRY. 


cona  w^e  30  Ibs.  to  a  height  of  200  feet ;  then 
the  latter  has  expended  twice  as  much  force 
as  the  former.  A  third  who  raises  60  Ibs.  to 
a  height  of  50  feet,  expends  no  more  force 
than  the  iirst  did  in  raising  30  Ibs.  to  the 
height  of  100  feet.  The  momentum  of  mo- 
tion of  the  first  (30x100)  is  equal  to  that 
of  the  third  (60x50)  while  that  of  the  se- 
cond (30x200)  is  twice  as  great. 

Momentum  of  force  and  momentum  of 
motion  in  mechanics  are  therefore  expres- 
sions or  measures  for  effects  of  force,  having 
reference  to  the  velocity  attained  in  a  given 
time,  or  to  a  given  space ;  and  in  this  sense 
may  be  applied  to  the  effects  of  all  other 
causes  of  motion,  or  of  change  in  form  and 
structure,  however  great  or  however  small 
may  be  the  space  or  the  time  in  which  their 
effects  are  displayed  to  the  senses. 

Every  force,  therefore,  exhibits  itself  in 
matter  either  in  the  form  of  resistance  to 
external  causes  of  motion,  or  of  change  in 
form  and  structure;  or  as  a  moving  force 
when  no  resistance  is  opposed  to  it;  or, 
finally,  in  overcoming  resistance. 

One  and  the  same  force  communicates 
motion  and  destroys  motion ;  the  former 
when  its  manifestations  are  opposed  by  no 
resistance  ;  the  latter,  when  it  puts  a  stop  to 
the  manifestation  of  some  other  cause  of 
motion,  or  of  change  in  form  and  structure. 
Equilibrium  or  rest  is  that  state  of  activity 
in  which  one  force  or  momentum  of  motion 
is  destroyed  by  an  opposite  force  or  momen- 
tum of  motion. 

We  observe  both  these  manifestations  of 
activity  in  that  force  which  gives  to  the  liv- 
ing tissues  their  peculiar  properties. 

The  vital  force  appears  as  a  moving  force 
or  cause  of  motion  when  it  overcomes  the 
chemical  forces  (cohesion  and  affinity)  which 
act  between  the  constituents  of  food,  and 
when  it  changes  the  position  or  place  in 
which  their  elements  occur;  it  is  manifested 
as  a  cause  of  motion  in  overcoming  the  che- 
mical attraction  of  the  constituents  of  food, 
and  is,  further,  the  cause  which  compels 
them  to  combine  in  a  new  arrangement,  and 
to  assume  new  forms. 

It  is  plain  that  a  part  of  the  animal  body 
possessed  of  vitality,  which  has  therefore  the 
power  of  overcoming  resistance,  and  of  giv- 
ing motion  to  the  elementary  particles  of  the 
food,  by  means  of  the  vital  force  manifested 
in  itself  must  have  a  momentum  of  motion, 
which  is  nothing  else  than  the  measure  of 
the  resulting  motion  or  change  in  form  and 
etructure. 

We  know  that  this  momentum  of  motion 
in' the  vital  force,  residing  in  a  living  part, 
may  be  employed  in  giving  motion  to  bodies 
at  rest,  (that  is,  in  causing  decomposition, 
or  overcoming  resistance,)  and  if  the  vital 
force  is  analogous  in  its  manifestations  to 
other  forces,  this  momentum  of  motion  must 
be  capable  of  being  conveyed  or  communi- 
cated by  matters,  which  in  themselves  do 
not  destroy  its  effect  by  an  opposite  mani- 
festation of  force. 


Motion,  by  whatever  cause  produced, 
cannot  in  itself  be  annihilated  ;  it  may  indeed 
become  inappreciable  to  the  senses,  buteveu 
when  arrested  by  resistance  (by  the  mani- 
festation of  an  opposite  force,)  its  effect  is 
not  annihilated.  The  falling  stone,  by  means 
of  the  amount  of  motion  acquired  in  its  de- 
scent, produces  an  effect  when  it  reaches 
the  table.  The  impression  made  on  the 
wood,  the  velocity  communicated  by  its 
parts  to  those  of  the  wood,  all  this  is  its  effect. 

If  we  transfer  the  conceptions  of  motion, 
equilibrium,  and  resistance,  to  the  chemical 
forces,  which,  in  their  modus  operandi,  ap- 
proach to  the  vital  force  infinitely  nearer 
than  gravitation  does,  we  know  with  the 
utmost  certainty,  that  they  are  active  only 
in  the  case  of  immediate  contact.  We  know, 
also,  that  the  unequal  capacity  of  chemical 
compounds  to  offer  resistance  to  external 
disturbing  influences,  to  those  of  heat,  or  of 
electricity,  which  tend  to  separate  their  par- 
ticles, as  well  as  their  power  of  overcoming 
resistance  in  other  compounds  (of  causing 
decomposition);  that,  in  a  word,  the  active 
force  in  a  compound  depends  on  a  certain 
order  or  arrangement,  in  which  its  element- 
ary particles  touch  each  other. 

The  same  elements,  united  in  a  different 
order,  when  in  contact  with  other  com- 
pounds, exert  a  most  unequal  power  of  of- 
fering or  overcoming  resistance.  In  one 
form  the  force  manifested  is  available  (the 
body  is  active,  an  acid,  for  example)  ;  in 
another  not  (the  body  is  indifferent,  neutral) ; 
in  a  third  form,  the  momentum  of  force  is 
opposed  to  that  of  the  first  (the  body  is 
active,  but  a  base). 

If  we  alter  the  arrangement  of  the  ele- 
ments, we  are  able  to  separate  the  constitu- 
ents of  a  compound  by  means  of  another 
active  body ;  while  the  same  elements,  united 
in  their  original  order,  would  have  opposed 
an  invincible  resistar.  ce  to  the  action  of  the 
decomposing  agent. 

In  the  same  way  as  two  equal  .nelastic 
masses,  impelled  with  equal  velocity  from 
opposite  points,  on  coming  into  contact  are 
brought  to  rest ;  in  the  same  way,  therefore, 
as  two  equal  and  opposite  momenta  of  mo- 
tion mutually  destroy  each  other;  so  may 
the  momentum  of  force  in  a  chemical  corn- 
pound  be  destroyed  in  whole  or  in  part  by 
an  equal  or  unequal,  and  opposite  momen- 
tum of  force  in  a  second  compound.  But 
it  cannot  be  annihilated  as  long  as  the  ar- 
rangement of  'he  elementary  particles,  by 
which  its  inherent  force  was  manifested,  is 
not  changed. 

The  chemical  force  of  sulphuric  acid  is 
present  in  sulphate  of  lime  as  entire  as  in 
oil  of  vitriol.  It  is  not  appreciable  by  the 
senses;  but  if  the  cause  be  removed  which 
prevented  its  manifestation,  it  appears  in  its 
full  force  in  the  compound  in  which  it  pro- 
perly resides. 

Thus  the  force  of  cohesion  in  a  solid  may 
disappear,  to  the  senses,  from  the  action  of" 
a  chemical  force,  (in  solution,)  or  of  heat 


MOTION   IN   THE   ANIMAL   ORGANISM. 


(in  fusion,)  without  being  in  reality  annihi- 
lated or  even  weakened.  If  we  remove  the 
opposing  force  or  resistance,  the  force  of  co- 
hesion appears  unchanged  in  crystallization. 

By  means  of  the  .electrical  force,  or  that 
of  heat,  we  can  give  the  most  varied  direc- 
tions to  the  manifestations  of  chemical  force. 
By  these  means  we  can  fix,  as  it  were,  the 
order  in  which  the  elementary  particles 
shall  unite.  Let  us  remove  the  cause  (heat 
or  electricity)  which  has  turned  the  balance 
in  favour  of  the  weaker  attraction  in  one 
direction,  and  the  stronger  attraction  will 
show  itself  continually  active  in  another 
direction ;  and  if  this  stronger  attraction  can 
overcome  the  vis  inertiae  of  the  elementary 
particles,  they  will  unite  in  a  new  form, 
and  a  new  compound  of  different  properties 
must  be  the  result. 

In  compounds  of  this  kind,  in  which, 
therefore,  the  free  manifestation  of  the 
chemical  force  has  been  impeded  by  other 
forces,  a  blow,  or  mechanical  friction,  or  the 
sontact  of  a  substance,  the  particles  of 
which  are  in  a  state  of  motion  (decomposi- 
tion, transformation,)  or  any  external  cause, 
whose  activity  is  added  to  the  stronger  at- 
traction of  the  elementary  particles  in  an- 
other direction,  may  suffice  to  give  the  pre- 
ponderance to  this  stronger  attraction,  to 
overcome  the  vis  inertise,  to  alter  the  form 
and  structure  of  the  compound,  which  are 
the  result  of  foreign  causes,  and  to  produce 
the  resolution  of  the  compound  into  one  or 
more  Hew  compounds  with  altered  proper- 
ties 

Transformations,  or  as  they  may  be  called", 
phenomena  of  motion,  in  compounds  of 
this  class,  may  be  effected  by  means  of  the 
free  and  available  chemical  force  of  another 
chemical  compound,  and  that  without  its 
manifestation  being  enfeebled  or  arrested  by 
resistance.  Thus  the  equilibrium  in  the  at- 
traction between  the  elements  of  cane-sugar 
is  destroyed  by  contact  with  a  very  small 
quantity  of  sulphuric  acid,  and  it  is  con- 
verted into  grape-sugar.  In  the  same  way 
we  see  the  elements  of  starch,  under  the 
same  influence,  arrange  themselves  with 
those  of  water  in  a  new  form,  while  the 
sulphuric  acid,  which  has  served  to  produce 
these  transformations,  loses  nothing  of  its 
chemical  character.  In  regard  toother  sub- 
stances on  which  it  acts,  it  remains  as  active 
as  before,  exactly  as  if  it  had  exerted  no 
sort  of  influence  on  the  cane-sugar  or  starch. 

In  contradistinction  to  the  manifestionsof 
the  so-called  mechanical  forces,  we  have 
recognized  in  the  chemical  forces  causes  of 
motion  and  of  change  in  form  and  structure, 
without  any  observable  exhaustion  of  the 
force  by  which  these  phenomena  are  pro- 
duced ;  but  the  origin  of  the  continued  mani- 
festation of  activity  remains  still  the  same; 
it  is  the  absence  of  an  opposite  force  (a  re- 
sistance) capable  of  neutralizing  it  or  bring- 
ing it  into  the  state  of  equilibrium. 

As  the  manifestations  of  chemical  forces 
(th-*  uittuientum  of  force  in  a  chemical 


compound)  seem  to  depend  on  a  certain 
order  in  which  the  elementary  particles  are 
united  together,  so  experience  tells  us,  that 
the  vital  phenomena  are  inseparable  from 
matter;  that  the  manifestations  of  the  vital 
force  in  a  living  part  are  determined  by  a 
certain  form  of  that  part,  and  by  a  certain 
arrangement  of  its  elementary  particles.  If 
we  destroy  the  form,  or  alter  the  composi- 
tion of  the  organ,  all  manifestations  of  vi- 
tality disappear. 

There  is  nothing  to  prevent  us  from  con- 
sidering the  vital  force  as  a  peculiar  pio- 
perty,  which  is  possessed  by  certain  mate- 
rial bodies,  and  becomes  sensible  when  their 
elementary  particles  are  combined  in  a  cer- 
tain arrangement  or  form. 

This  supposition  takes  from  the  vital 
phenomena  nothing  of  their  wonderful  pe- 
culiarity; it  may  therefore  be  considered  as 
a  resting  point,  from  which  an  investigation 
into  these  phenomena,  and  the  laws  which 
regulate  them,  may  be  commenced;  exactly 
as  we  consider  the  properties  and  laws  of 
light  to  be  dependent  on  a  certain  luminife- 
rous  matter,  or  other,  which  has  no  further 
connexion  with  the  laws  ascertained  by  in- 
vestigation. 

Considered  under  this  form,  the  vital  force 
unites  in  its  manifestations  all  the  peculiari- 
ties of  chemical  forces,  and  of  the  not  less 
wonderful  cause,  which  we  regard  as  the 
ultimate  origin  of  electrical  phenomena. 

The  vital  force  does  not  act,  like  the  force 
of  gravitation  or  the  magnetic  force,  at  in-, 
finite  distances,  but,  like  chemical  forces,  itj 
is  active  only  in  the  case  of  immediate  con-j 
_tact.  It  becomes  sensible  by  means  of  an" 
"aggregation  of  material  particles. 

A  living  part  acquires,  on  the  above  sup- 
position, the  capacity  of  offering  and  of 
overcoming  resistance,  by  the  combination 
of  its  elementary  particles  in  a  certain  form ; 
and  as  long  as  its  form  and  composition  are 
not  destroyed  by  opposing  forces,  it  must  re- 
tain its  energy  uninterrupted  and  unimpaired. 

When,  by  the  act  of  manifestation  of  this 
energy  in  a  living  part,  the  elements  of  the 
food  are  made  to  unite  in  the  same  form  and 
structure  as  the  living  organ  possesses,  then 
these  elements  acquire  the  same  powers. 
By  this  combination,  the  vital  force  inherent 
in  them  is  enabled  to  manifest  itself  freely, 
and  may  be  applied  in  the  same  way  as  that 
of  the  previously  existing  tissue. 

If,  now,  we  bear  in  mind,  that  all  matters 
which  serve  as  food  to  living  organisms  are 
compounds  of  two  or  more  elements,  which 
are  kept  together  by  certain  chemical  forces; 
if  we  reflect  that  in  the  act  of  manifestation 
offeree  in  a  living  tissue,  the  elements  of 
the  food  a're  made  to  combine  in  a  new 
order; — it  is  quite  certain  thai  the  momen- 
tum of  force  or  of  motion  in  the  vital  force 
was  more  powerful  than  the  chemical  at- 
traction existing  between  the  elements  of  the 
food.* 


*  The  hands  of  a  man.  who  raises  with 


ANIMAL   CHEMISTRY. 


The  chemical  force  which  kept  the  ele- 
ments together  acted  as  a  resistance/ which 
was  overcome  by  the  active  vital  force. 

Had  both  forces  been  equal,  no  kind  of 
sensible  effect  would  have  ensued.  Had  the 
chemical  force  been  the  stronger,  the  living 
part  would  have  undergone  a  change. 

If  we  now  suppose  that  a  certain  amount 
of  vita]  force  must  have  been  expended  in 
bringing  to  an  equilibrium  the  chemical 
force,  there  must  still  remain  an  excess  of 
force,  by  which  the  decomposition  was  ef- 
fected. This  excess  constitutes  the  mo- 
mentum of  force  in  the  living  part,  by 
means  of  which  the  change  was  produced ; 
by  means  of  this  excess  the  part  acquires  a 
permanent  power  of  causing  further  decom- 
positions, and  of  retaining  its  condition, 
form,  and  structure,  in  opposition  to  exter- 
nal agencies. 

We  may  imagine  this  excess  to  be  re- 
moved, and  employed  in  some  other  form. 
This  would  not  of  itself  endanger  the  exist- 
ence of  the  living  part,  because  the  opposing 
forces  would  be  left  in  equilibrio ;  but,  by 
the  removal  of  the  excess  of  force,  the  part 
would  lose  its  capacity  of  growth,  its  power 
to  cause  further  decompositions,  and  its 
ability  to  resist  external  causes  of  change. 
If,  in  this  state  of  equilibrium,  oxygen  (a 
chemical  agent)  should  be  brought  in  con- 
tact with  it,  then  there  would  be  no  resist- 
ance to  the  tendency  of  the  oxygen  to  com- 
b.ae  with  some  element  of  the  living  part, 
because  its  power  of  resistance  has  been 
taken  away  by  some  other  application  of  its 
excess  of  vital  force.  According  to  the 
amount  of  oxygen  brought  to  it,  a  certain 
proportion  of  the  living  part  would  lose  its 
condition  of  vitality,  and  take  the  form  of  a 
chemical  combination,  having  a  composi- 
tion different  from  that  of  the  living  tissue. 
In  a  word,  there  would  occur  a  change  in 
the  properties  of  the  living  compound,  or 
what  we  have  called  a  change  of  matter. 

If  we  reflect  that  the  capacity  of  growth 
or  increase  of  mass  in  plants  is  almost  un- 
limited ;  that  a  hundred  twigs  from  a  willow 
tree,  if  placed  in  the  soil,  become  a  hundred 
jrees ;  we  can  hardly  entertain  a  doubt,  that 
with  the  combination  of  the  elements  of  the 
food  of  the  plant  so  as  to  form  a  part  of  it, 
a  fresh  momentum  of  force  is  added  in  the 
newly  formed  part  to  the  previously  existing 
momentum  in  the  plant;  insomuch,  that 
with  the  increase  of  mass,  the  sum  of  vital 
force  is  augmented. 

According  to  the  amount  of  available  vital 
force,  the  products  formed  by  its  activity 
from  the  food  are  varied.  The  composition 


and  simple  pulley,  30  Ibs.  to  the  height  of  100 
feet,  pass  over  a  space  of  100  feet,  while  his  mus- 
cular energy  furnishes  the  equilibrium  to  a  pres- 
sure of  30  Ibs.  Were  the  force  which  the  man 
could  exert  not  greater  than  would  suffice  to  keep 
in  equilibrium  a  pressure  of  30  Ibs.,  he  would  be 
unable  to  raise  the  weight  to  the  height  men- 
tioned. 


1  of  the  buds,  of  the  radical  fibres,  of  the  leaf, 
of  the  flower,  and  of  the  fruit,  are  very  dif- 
|  ferent  one  from  the  other ;  and  the  chemical 
force  by  which  their  elements  are  held  toge- 
ther is  very  different  in  each  of  these  cases. 

Of  the  non-azotized  constituents  of  plants 
we  may  assert,  that  no  part  of  the  momen- 
tum of  force  is  expended  in  maintaining 
their  form  and  structure,  when  their  ele- 
ments have  once  combined  in  that  order  in 
which  they  become  parts  of  organs  endued 
with  vitality. 

Very  different  is  the  character  of  the  azo- 
tized  vegetable  principles;  for,  when  sepa- 
rated from  the  plant,  they  pass,  as  is  com- 
monly said,  spontaneously,  into  fermentation 
and  putrefaction.  The  cause  of  this  de- 
composition or  transformation  of  their  ele- 
ments is  the  chemical  action  which  the 
oxygen  of  the  atmosphere  exercises  on  one 
of  their  constituents.  Now  we  know,  that 
as  long  as  the  plant  exhibits  the  phenomena 
of  life,  oxygen  gas  is  given  off  from  its  sur- 
face ;  that  this  oxygen  is  altogether  without 
action  on  the  constituents  of  the  living  plant, 
for  which,  in  other  circumstances,  it  has  the 
strongest  attraction.  It  is  obvious,  there- 
fore, that  a  certain  amount  of  vital  force 
must  be  expended,  partly  to  retain  the  de- 
ments of  the  complex  azotized  principles  in 
the  form,  order,  and  structure  which  belong 
to  them ;  and  partly  as  a  means  of  resistance 
against  the  incessant  tendency  of  the  oxygen 
of  the  atmosphere  to  act  on  their  elements, 
as  well  as  against  that  of  the  oxygen  se- 
parated in  the  organism  of  the  plant  b'y  the 
vital  process. 

With  the  increase  of  these  easily  altered 
compounds,  in  the  flower  and  in  the  fruit, 
for  example,  the  sum  of  chemical  force  (the 
free  manifestation  of  which,  counteracted  by 
an  equal  measure  of  vital  force,  is  employed 
to  furnish  resistance)  also  increases. 

The  plant  increases  in  mass  until  the  vital 
force  inherent  in  it  comes  into  equilibrium 
with  all  the  other  causes  opposed  to  its 
manifestation.  From  this  period,  every  new 
cause  of  disturbance,  added  to  those  pre- 
viously existing  (a  change  of  .temperature, 
for  example,)  deprives  it  of  the  power  of  of- 
fering resistance,  and  it  dies  down. 

In  perennial  plants  (in  trees,  for  example,) 
the  mass  of  the  easily  decomposable  (azo- 
tized) compounds,  compared  with  that  of 
the  non-azotized,  is  so  small,  that  of  the 
whole  sum  of  force,  only  a  minimum  is 
expended  as  resistance.  In  animals,  this 
proportion  is  reversed. 

During  every  period  of  the  life  of  a  plant, 
the  available  vital  force  (that  which  is  not 
neutralized  by  resistance)  is  expended  only 
in  one  form  of  vital  manifestation,  that  of 
growth  or  increase  of  mass,  or  the  over- 
coming of  resistance.  No  part  of  this  force 
is  applied  to  other  purposes. 

In  the  animal  organism,  the  vital  force 
exhibits  itself,  as  in  the  plant,  in  the  form 
of  the  capacity  of  growth,  and  as  the  means 
of  resistance  to  external  agencies  ;  but  both 


MOTION   IN   THE   ANIMAL   ORGANISM. 


65 


of  these  manifestations  are  confined  within  ; 
certain  limits. 

We  observe  in  animals,  that  the  conver- 
sion of  food  into  blood,  and  the  contact  of 
the  blood  with  the  living  tissues,  are  deter- 
mined by  a  mechanical  force,  whose  mani- 
festation proceeds  from  distinct  organs,  and 
is  effected  by  a  distinct  system  of  organs, 
possessing  the  property  of  communicating 
and  extending  the  motion  which  they  re- 
ceive. We  find  the  power  of  the  animal  to 
change  its  place  and  to  produce  mechanical 
effects  by  means  of  its  limbs,  dependent  on 
a  second  similar  system  of  organs  or  appa- 
ratus. Both  of  these  systems  of  apparatus, 
as  well  as  the  phenomena  of  motion  pro- 
ceeding from  them,  are  wanting  in  plants. 

In  order  to  form  a  clear  conception  of  the 
origin  and  source  of  the  mechanical  mo- 
tions in  the  animal  body,  it  may  be  advan- 
tageous to  reflect  on  the  modus  operand!  of 
other  forces,  which  in  their  manifestations 
are  most  closely  allied  to  the  vital  force. 

When  a  number  of  plates  of  zinc  and 
copper,  arranged  in  a  certain  order,  are 
brought  into  contact  with  an  acid,  and  when 
the  extremities  of  the  apparatus  are  joined 
by  means  of  a  metallic  wire,  a  chemical  ac- 
tion begins  at  the  surface  of  the  plates  of 
zinc,  and  the  wire,  in  consequence  of  this 
action,  acquires  the  most  singular  and  won- 
derful properties. 

The  wire  appears  as  the  carrier  or  con- 
ductor of  a  force,  which  may  be  conducted 
and  communicated  through  it  in  every  di- 
rection with  amazing  velocity.  It  is  the 
conductor  or  propagator  of  an  uninterrupted 
series  of  manifestations  of  activity. 

Such  a  propagation  of  motion  is  incon- 
ceivable, if  in  the  wire  there  were  a  resist- 
ance to  be  overcome ;  for  every  resistance 
would  convert  a  part  of  the  moving  force 
into  a  force  at  rest. 

When  the  wire  is  divided  in  the  middle, 
and  its  continuity  interrupted,  the  propaga- 
tion of  force  ceases,  and  we  observe,  that  in 
this  case  the  action  between  the  zinc  and 
the  acid  is  immediately  stopped. 

If  the  communication  be  restored,  the  ac- 
tion which  had  disappeared  reappears  with 
all  its  original  energy. 

By  means  of  the  force  present  in  the 
wire,  we  can  produce  the  most  varied  ef- 
fects ;  we  can  overcome  all  kinds  of  resist- 
ance, raise  weights,  set  ships  in  motion,  &c. 
And,  what  is  still  more  remarkable,  the 
wire  acts  as  a  hollow  tube,  in  which  a  cur- 
rent of  chemical  force  circulates  freely  and 
without  hindrance. 

Those  properties  which,  when  firmly  at- 
tached to  certain  bodies,  we  call  the  strongest 
and  most  energetic  affinities,  we  find,  to  all 
appearance,   free    and    uncombined  in  the 
\vire.     We    can    transport   them   from  the 
wire   to  other  bodies,  and  thereby  give  to 
them  an  affinity  (a  power  of  entering  into 
combination)  which  in  themselves  they  do  | 
not  possess.     According  to  the  amount  of  j 
force  circulating  in  the  wire,  we  are  able  by  I 


means  of  it  to  decompose  compounds,  the 
elements  of  which  have  the  strongest  at- 
traction for  each  other.  Yet  the  substance 
of  the  wire  takes  not  the  smallest  share  in 
all  these  manifestations  of  force ;  it  is 
merely  the  conductor  of  force. 

We  observe,  further,  in  this  wire,  phe- 
nomena of  attraction  and  repulsion,  which 
we  must  ascribe  to  the  disturbance  of  the 
equilibrium  in  the  electric  or  magnetic 
force ;  and  when  this  equilibrium  is  restored, 
the  restoration  is  accompanied  by  the  de- 
velopement  of  light  and  heat,  its  never-fail- 
ing companions. 

All  these  remarkable  phenomena  are  pro- 
duced by  the  chemical  action  which  the 
zinc  and  the  acid  exert  on  each  other ;  they 
are  accompanied  by  a  change  in  form  and 
structure,  which  both  undergo. 

The  acid  loses  its  chemical  character ;  the 
zinc  enters  into  combination  with  it.  The 
manifestations  of  force  produced  in  the  wire 
are  the  immediate  consequence  of  the 
change  in  the  properties  of  the  acid  and  the 
metal. 

One  particle  of  acid  after  another  loses  its 
peculiar  chemical  character;  and  we  per- 
ceive that  in  the  same  proportion  the  wire 
acquires  a  chemical,  mechanical,  galvanic, 
or  magnetic  force,  whatever  name  be  given 
to  it.  According  to  the  number  of  acid 
particles  which  in  a  given  time  undergo 
this  change,  that  is,  according  to  the  sur- 
face of  the  zinc,  the  wire  receives  a  greater 
or  less  amount  of  these  forces. 

The  continuance  of  the  current  of  force 
depends  on  the  duration  of  the  chemical  ac- 
tion ;  and  the  duration  of  the  latter  is  most 
closely  connected  with  the  carrying  away, 
by  conduction,  of  the  fdVce. 

If  we  check  the  propagation  of  the  cur- 
rent of  force,  the  acid  retains  its  chemical 
character.  If  we  employ  it  to  overcome 
chemical  or  mechanical  resistance,  to  de 
compose  chemical  compounds,  or  to  pro- 
duce motion,  the  chemical  action  continues  j 
that  is  to  say,  one  particle  of  acid  after 
another  changes  its  properties. 

In  the  preceding  paragraphs  we  have 
considered  these  remarkable  phenomena  in 
a  form  which  is  independent  of  the  explana- 
tions of  the  schools.  Is  the  force  which 
circulates  in  the  wire  the  electrical  force? 
Is  it  chemical  affinity?  Is  it  propagated  in 
the  conductor  like  a  fluid  set  in  motion,  or 
in  the  form  of  a  series  of  momenta  of  mo- 
tion, like  light  and  sound,  from  one  particle 
of  the  conductor  to  another  ?  All  this  we 
know  not,  and  we  shall  never  know.  All 
the  suppositions  which  may  be  employed 
as  explanations  of  the  phenomena  have  not 
the  slightest  influence  on  the  truth  of  these 
phenomena;  for  they  refer  merely  to  the 
form  in  which  they  are  manifested. 

On  some  points,  however,  there  is  no 
doubt;  namely,  that  all  the  effects  which 
may  be  produced  by  the  wire  are  deter- 
mined by  the  change  of  properties  in  the 
zinc  and  in  the  acid  ;  for  the  term  "  chemi- 


AMIVfAL  CHEMISTRY. 


cal  action"  signifies  neither  more  nor  less 
than  the  act  of  change  in  them ;  that  these 
effects  depend  on  the  presence  of  a  conduc- 
tor, of  a  substance  which  propagates  in  all 
directions,  where  it  is  not  neutralized  by  re- 
sistance, the  force  or  momentum  produced  ; 
that  this  force  becomes  a  momentum  of 
motion,  by  means  of  which  we  can  produce 
mechanical  effects,  and  which,  when  trans- 
ferred to  other  bodies,  communicates  to 
them  all  those  properties,  the  ultimate  cause 
of  which  is  the  chemical  force  itself;  for 
these  bodies  acquire  the  power  of  causing 
decompositions  and  combinations,  such  as, 
without  a  supply  of  force  through  the  con- 
ductor, they  could  not  effect. 

If  we  employ  these  well  known  facts  as 
means  to  assist  us  in  investigating  the  ulti- 
mate cause  of  the  mechanical  effects  in  the 
animal  organism,  observation  teaches  us, 
that  the  motion  of  the  blood  and  of  the  other 
animal  fluids  proceeds  from  distinct  organs 
which,  as  in  the  case  of  the  heart  and  in- 
testines, do  not  generate  the  moving  power 
in  themselves,  but  receive  it  from  other 
quarters. 

We  know  with  certainty  that  the  nerves 
are  the  conductors  and  propagators  of  me- 
chanical effects;  we  know,  that  by  means  of 
them  motion  is  propagated  in  all  directions. 
For  each  motion  we  recognize  a  separate 
nerve,  a  peculiar  conductor,  with  the  con- 
ducting power  of  which,  or  with  its  inter- 
ruption, the  propagation  of  motion  is  affected 
or  destroyed. 

By  means  of  the  nerves  all  parts  of  the 
body,  all  the  limbs,  receive  the  moving  force 
which  is  indispensable  to  their  functions,  to 
change  of  place,  to  the  production  of  me- 
chanical effects.  Where  nerves  are  not 
found,  motion  does  not  occur.  The  excess 
of  force  generated  in  one  place  is  conducted 
to  other  parts  by  the  nerves.  The  force 
which  one  organ  cannot  produce  in  itself  is 
conveyed  to  it  from  other  quarters ;  and  the 
vital  force  which  is  wanting  to  it,  in  order 
to  furnish  resistance  to  external  causes  of 
disturbance,  it  receives  in  the  form  of  excess 
from  another  organ,  an  excess  which  that 
organ  cannot  consume  in  itself. 

We  observe  further,  that  the  voluntary 
and  involuntary  motions,  in  other  words,  all 
mechanical  effects  in  the  animal  organism, 
are  accompanied  by,  nay,  are  dependent  on, 
a  peculiar  change  of  form  and  structure  in 
the  substance  of  certain  living  parts,  the  in- 
crease or  diminution  of  which  change  stands 
in  the  very  closest  relation  to  the  measure  of 
motion,  or  the  amount  of  force  consumed 
in  the  motions  performed. 

As  an  immediate  effect  of  the  manifesta- 
tion of  mechanical  force,  we  see,  that  a  part 
of  the  muscular  substance  loses  its  vital 
properties,  its  character  of  life;  that  this 
portion  separates  from  the  living  part,  and 
loses  its  capacity  of  growth  and  its  power  of 
resistance.  We  find  that  this  change  of 
properties  is  accompanied  by  the  entrance 
of  a  foreign  body  (oxygen)  into  the  composi- 


tion of  the  muscular  fibre  (just  as  tne  acid 
lost  its  chemical  character  by  combining 
j  with  zinc  ;)  and  all  experience  proves,  that 
I  this  conversion  of  living  muscular  fibre  into 
compounds  destitute  of  vitality  is  accelerated 
or  retarded  according  to  the  amount  offeree 
employed  to  produce  motion.  Nay,  it  may 
safely  be  affirmed,  that  they  are  mutually 
proportional ;  that  a  rapid  transformation  of 
muscular  fibre,  or,  as  it  may  be  called,  a 
rapid  change  of  matter,  determines  a  greater 
I  amount  of  mechanical  force ;  and  con- 
j  versely,  that  a  greater  amount  of  me- 
I  chanical  motion  (of  mechanical  force  ex- 
pended in  motion)  determines  a  more  rapid 
change  of  matter. 

Prom  this  decided  relation  between  the 
change  of  matter  in  the  animal  body  and  the 
force  consumed  in  mechanical  motion,  no 
other  conclusion  can  be  drawn  but  this,  that 
the  active  or  available  vital  force  in  certain 
living  parts  is  the  cause  of  the  mechanical 
phenomena  in  the  animal  organism. 

The  moving  force  certainly  proceed?  from 
living  parts;  these  parts  possessed  a  mo- 
mentum of  force  or  of  motion,  which  they 
lost  in  proportion  as  other  parts  acquired 
a  momentum  of  force  or  of  motion;  they 
lose  their  capacity  of  growth,  and  their 
power  to  resist  external  causes  of  change. 
It  is  obvious  that  the  ultimate  cause,  the 
vital  force,  from  which  they  acquired  these 
properties,  has  served  for  the  production  of 
mechanical  force,  that  is,  has  been  expended 
in  the  shape  of  motion. 

How,  indeed,  could  we  conceive  that  a 
living  part  should  lose  the  condition  of  life, 
should  become  incapable  of  resisting  the 
action  of  the  oxygen  conveyed  to  it  by  the 
arterial  blood,  and  should  be  deprived  of  the 
power  to  overcome  chemical  resistance, 
unless  the  momentum  of  the  vital  force, 
which  had  given  to  it  all  these  properties, 
had  been  expended  for  other  purposes  1 

By  the  power  of  the  conductors,  the 
nerves  to  propagate  the  momentum  of  force 
in  a  living  part,  or  the  effect  which  the 
active  vital  force  inherent  in  the  part  pro, 
duces  on  all  the  surrounding  parts,  in  all 
directions  where  the  force,  or  rather  its  mo- 
mentum of  motion,  is  consumed  without 
resistance,  (for  without  motion  no  change 
of  matter  occurs,  and  when  motion  has 
begun,  there  is  no  longer  resistance,)  an 
equilibrium  is  obviously  established  in  the 
living  part,  between  the  chemical  forces  and 
the  remaining  vital  force ;  which  equilibrium 
would  not  have  occurred  had  not  vital 
force  been  expended  in  producing  me- 
chanical motion. 

In  this  state,  any  external  cause  capable 
of  exerting  an  influence  on  the  form,  struc- 
ture and  composition  of  the  organ  meets 
with  no  further  resistance.  If  oxygen  were 
not  conveyed  to  it,  the  organ  would  main- 
tain its  condition,  but  without  any  mani- 
festation of  vitality.  It  is  only  with  the 
commencement  of  chemical  action  that  the 
change  of  matter,  that  is,  the  separation  of 


MOTION   IN   THE   ANIMAL   ORGANISM. 


67 


a  part  of  the  organ  in  the  form  of  lifeless 
compounds,  begins. 

The  change  of  matter,  the  manfestation 
of  mechanical  force,  and  the  absorption  of 
oxygen,  are,  in  the  animal  body,  so  closely 
connected  with  each  other,  that  we  may 
consider  the  amount  of  motion,  and  the 
quantity  of  living  tissue  transformed,  as  pro- 
portional to  the  quantity  of  oxygen  inspired 
and  consumed  in  a  given  time  by  the 
animal.  For  a  certain  amount  of  motion, 
for  a  certain  proportion  of  vital  force  con- 
sumed as  mechanical  force,  an  equivalent 
of  chemical  force  is  manifested;  that  is,  an 
equivalent  of  oxygen  enters  into  combina- 
tion with  the  substance  of  the  organ  which 
has  lost  the  vital  force  ;  and  a  corresponding 
proportion  of  the  substance  of  the  organ  is 
separated  from  the  living  tissue  in  the  shape 
of  an  oxidized  compound. 

All  those  parts  of  the  body  which  nature 
has  destined  to  effect  the  change  of  matter, 
that  is,  to  the  production  of  mechanical  force, 
are  penetrated  in  all  directions  by  a  multi- 
tude of  the  most  minute  tubes  or  vessels,  in 
which  a  current  of  oxygen  continually  cir- 
culates, in  the  form  of  arterial  blood.  To 
the  above-mentioned  separation  of  part  of 
the  elements  of  these  parts,  in  other  words, 
to  the  disturbance  of  their  equilibrium,  this 
oxygen  is  absolutely  essential. 

As  long  as  the  vital  force  of  these  parts 
is  not  conducted  away  and  applied  to  other 
purposes,  the  oxygen  of  the  arterial  blood 
has  not  the  slightest  effect' on  the  substance 
of  the  organized  parts;  and  in  all  cases, 
only  so  much  oxygen  is  taken  up  as  cor- 
responds to  the  conducting  power,  and,  con- 
sequently to  the  mechanical  effects  produced. 

The  oxygen  of  the  atmosphere  is  the 
proper,  active,  external  cause  of  the  waste 
of  matter  in  the  animal  body :  it  acts  like  a 
force  which  disturbs  and  tends  to  destroy 
the  manifestation  of  the  vital  force  at  every 
moment.  But  its  effect  as  a  chemical  agent, 
the  disturbance  proceeding  from  it,  is  held 
in  equilibrium  by  the  vital  force,  which  is 
free  and  available  in  the  living  tissue,  or  is 
annihilated  by  a  chemical  agency  opposed 
to  that  of  oxygen,  the  manifestation  of 
which  must  be  considered  as  dependent  on 
the  vital  force. 

In  chemical  language,  to  annihilate  the 
chemical  action  of  oxygen,  means,  to  pre- 
sent to  it  substances,  or  parts  of  organs, 
which  are  capable  of  combining  with  it. 

The  action  of  oxygen  (affinity)  is  either 
neutralized  by  means  of  the  elements  of 
organized  parts,  which  combine  with  it, 
(after  the  free  vital  force  has  been  conducted 
away,)  or  else  the  organ  presents  to  it  the 
products  of  other  organs,  or  certain  matters 
formed  from  the  elements  of  the  food,  by 
the  vital  activity  of  certain  systems  of  ap- 
paratus. 

It  is  only  the  muscular  system  which,  in 
this  sense,  produces  in  itself  a  resistance  to 
the  chemical  action  of  oxygen,  and  neutral- 
izes it  completely. 


The  substance  of  cellular  tissue,  of  mem- 
branes, and  of  the  skin,  the  minutest  parti- 
cles of  which  are  not  in  immediate  contact 
with  arterial  blood,  (with  oxygen,)  are  not 
destined  to  undergo  this  change  of  matter. 
Whatever  phanges  they  may  undergo  in 
the  vital  process,  affect,  in  all  cases,  only 
their  surface. 

The  gelatinous  tissues,  mucous  mem. 
branes,  tendons,  &c.,  are  not  designed  to 
produce  mechanical  force;  they  contain  in 
their  substance  no  conductors  ot  mechanical 
effects.  But  the  muscular  system  is  inter- 
woven with  innumerable  nerves.  The  sub- 
stance of  the  uterus  is  in  no  respect  different 
in  chemical  composition  from  the  other  mus- 
cles ;  but  it  is  not  adapted  to  the  change  of 
matter,  to  the  production  of  force,  and  con- 
tains no  organs  for  conducting  away  the 
moving  power.  Cellular  tissue,  gelatinous 
membranes,  and  mucous  membranes,  are 
far  from  being  destitute  of  the  power  of 
combining  with  oxygen,  when  moisture  is 
present ;  we  know  that,  when  moist,  they 
cannot  be  brought  in  contact  with  oxygen 
without  undergoing  a  progressive  alteration. 
But  one  surface  of  the  intestines  and  the 
cells  of  the  lungs  are  constantly  in  contact 
with  oxygen;  and  it  is  obvious  that  they 
must  be  as  rapidly  altered  by  the  chemical 
action  of  the  oxygen  in  the  body  as  out  of 
it,  were  it  not  that  there  exists  in  the  or- 
ganism itself  a  source  of  resistance,  which 
completely  neutralizes  the  action  of  the  oxy- 
gen. Among  the  means  by  which  this  re- 
sistance is  furnished  we  may  include  all 
substances  which  are  capablf  of  combining 
with  oxygen,  or  acquire  that  property  under 
the  influence  of  the  vital  force,  and  which 
surpass  the  tissues  above  mentioned  in  their 
power  of  neutralizing  its  chemical  action. 

All  those  constituents  of  the  body  which, 
in  themselves,  do  not  possess,  in  the  form 
of  vital  force,  the  power  of  resisting  the 
action  of  oxygen,  must  be  far  better  adapted 
for  the  purpose  of  combining  with,  and 
neutralizing  it,  than  those  tissues  which  are 
under  the  influence  of  the  vital  force,  al- 
though only  through  the  nerves.  In  this 
point  of  view,  we  cannot  fail  to  perceive 
the  importance  of  the  bile  in  regard  to  the 
substance  of  the  intestines,  and  that  of  the 
pulmonary  cells,  as  well  as  that  of  fat,  of 
mucus,  and  of  the  secretions  generally. 

When  the  membranes  are  compelled  from 
their  own  substance  to  furnish  resistance  to 
the  action  of  the  oxygen,  that  is,  when  there 
is  a  deficiency  of  the  substances  destined  by 
nature  for  their  protection,  they  must,  since 
their  renewal  is  confined  within  narrow 
limits,  yield  to  the  chemical  action.  The 
lungs  and  intestines  will  always  simulta- 
neously suffer  abormal  changes. 

From  the  change  of  matter  itself,  from 
the  metamorphosis  of  the  living  muscular 
tissue,  these  organs  receive  the  means  of 
resistance  to  the  action  of  oxygen  which  are 
indispensable  to  their  preservation.  Accord- 
ing to  the  rapidity  of  this  process,  the  quau- 


ANIMAL   CHEMISTRY. 


thy  of  bil  e  secreted  increases ;  while  that  of 
the  fat  present  in  the  body  diminishes  in  the 
same  proportion. 

For  carrying  on  the  involuntary  motions 
in  the  animal  body,  a  certain  amount  of  vital 
force  is  expended  at  every  moment  of  its 
existence;  and,  consequently,  an  incessant 
change  of  matter  goes  on;  but  the  amount 
of  living  tissue,  which,  in  consequence  of 
this  form  of  consumption  of  vital  force, 
loses  its  condition  of  life  and  its  capacity  of 

?rowth,  is  confined  within  narrow  limits, 
t  is  directly  proportional  to  the  force  re- 
quired for  these  involuntary  motions. 

Now,  although  we  may  suppose  that  the 
living  muscular  tissue,  with  a  sufficient  sup- 
ply of  food,  never  loses  its  capacity  of 
growth ;  that  this  form  of  vital  manifestation 
is  continually  effective ;  this  cannot  apply  to 
those  parts  of  the  body  whose  available  vital 
force  has  been  expended  in  producing  me- 
chanical effects.  For  the  waste  of  matter, 
in  consequence  of  motion  and  laborious 
exertion,  is  extremely  various  in  different 
individuals. 

If  we  reflect,  that  the  slightest  motion  of 
a  finger  consumes  force ;  that  in  conse- 
quence of  the  force  expended,  a  correspond- 
ing portion  of  muscle  diminishes  in  volume; 
it  is  obvims,  that  an  equilibrium  between 
supply  and  waste  of  matter  (in  living  tissues) 
can  only  occur  when  the  portion  separated 
or  expelled  in  a  lifeless  form  is,  at  the  same 
instant  in  which  it  loses  its  vital  condition, 
restored  in  another  part. 

The  capacity  of  growth  or  increase  in 
mass  depends  on  the  momentum  of  force 
belonging  to  each  part ;  and  must  be  capable 
of  continued  manifestation  (if  there  be  a  suf- 
ficient supply  of  nourishment,)  as  long  as  it 
does  not  lose  this  momentum,  by  expending 
it,  for  example,  in  producing  motion. 

In  all  circumstances,  the  growth  itself  is 
restricted  to  the  time :  that  is  to  say,  it  can- 
not be  unlimited  in  a  limited  time. 

A  living  part  cannot  increase  in  •volume 
at  the  same  moment  in  which  a  portion  of 
it  loses  the  vital  condition,  and  is  expelled 
from  the  organ  in  the  form  of  a  lifeless  com- 
pound ;  on  the  contrary,  its  volume  must 
diminish. 

The  continued  application  of  the  momen- 
tum of  force  in  living  tissues  to  mechanical 
effects  determines,  therefore,  a  continued 
separation  of  matter ;  and  only  from  the  pe- 
riod at  which  the  cause  of  waste  ceases  to 
operate,  can  the  capacity  of  growth  be  ma- 
nifested. 

Now,  since,  in  different  individuals,  ac- 
cording to  the  amount  of  force  consumed  in 
producing  voluntary  mechanical  effects,  un- 
equal quantities  of  living  tissue  are  wasted, 
there  must  occur,  in  every  individual,  unless 
the  phenomena  of  motion  are  to  cease  en- 
tirely, a  condition  in  which  all  voluntary 
motions  are  completely  checked,  in  which, 
therefore,  these  occasion  no  waste.  This 
condition  is  called  sleep. 

The  growth  of  one  part,  which  is  not  de- 


prived of  its  vital  force,  cannot  be  in  the 
slightest  degree  affected  by  the  consumption 
of  the  vital  force  of  another  part  in  producing 
motion.  The  one  may  increase  in  volume, 
while  the  other  diminishes ;  and  the  waste 
in  one  can  neither  increase  nor  diminish  the 
supply  in  the  other. 

Now,  since  the  consumption  of  force  for 
the  involuntary  motions  continues  in  sleep, 
it  is  plain  that  a  waste  of  matter  also  con- 
tinues in  that  state ;  and  if  the  original  equi- 
librium is  to  be  restored,  we  must  suppose 
that,  during  sleep,  an  amount  of  force  is  ac- 
cumulated in  the  form  of  living  tissue, 
exactly  equal  to  that  which  was  consumed 
in  voluntary  and  involuntary  motion  during 
the  preceding  waking  period. 

If  the  equilibrium  between  waste  and 
supply  of  matter  be  in  the  least  degree  dis- 
turbed, this  is  instantly  seen  in  the  different 
amount  of  force  available  for  mechanical 
purposes. 

It  is  further  obvious,  that  if  there  should 
occur  a  disproportion  between  the  conduct- 
ing power  of  the  nerves  of  voluntary  and 
involuntary  motion,  a  difference  in  the  phe- 
nomena of  motion  themselves  will  be  per- 
ceptible, in  the  same  proportion  as  the  one 
or  the  other  is  capable  of  propagating  the 
momentum  of  force,  generated  by  the  change 
of  matter.  As  the  motions  of  the  circulating 
system  and  of  the  intestines  increase,  the 
power  of  producing  mechanical  effects  in 
the  limbs  must  diminish  in  the  same  propor- 
tion (as  in  wasting  fevers ;)  and  it,  in  a  given 
time,  more  vital  force  has  been  consumed 
for  mechanical  purposes  (labour,  running, 
dancing,  &,c.,)  than  is  properly  available  for 
the  voluntary  and  involuntary  motions ;  if 
force  be  expended  more  rapidly  thin  the 
change  of  matter  can  be  effected  in  the  same 
time  ;  then  a  part  of  that  force  whi^h  is 
necessary  for  the  involuntary  motions  must 
be  expended  in  restoring  the  excess  of  force 
consumed  in  voluntary  motion.  The  mo- 
tions of  the  heart  and  of  the  intestines,  in 
this  case,,  will  be  retarded,  or  will  entirely 
cease. 

From  the  unequal  degree  of  conducting 
power  in  the  nerves,  we  must  deduce  those 
conditions  which  are  termed  paralysis,  syn- 
cope, and  spasm.  Paralysis  of  the  nerves 
of  voluntary  motion  may  exist  without  ema- 
ciation ;  but  frequently  recurring  attacks  of 
epilepsy  (in  which  vital  force  is  rapidly 
wasted  in  producing  mechanical  effects)  are 
always  accompanied  by  remarkably  rapid 
emaciation. 

It  ought  to  excite  the  highest  admiration 
when  we  consider  with  what  infinite  wis- 
dom the  Creator  has  divided  the  means  by 
which  animals  and  plants  are  qualified  for 
their  functions,  for  their  peculiar  vital  mani- 
festations. 

The  living  part  of  a  plant  requires  the 
whole  force  and  direction  of  its  vital  energy 
from  the  absence  of  all  conductors  of  force. 
By  this  means  the  leaf  is  enabled  to  over- 
come the  strongest  chemical  attractions,  to 


MOTION    OF   ANIMAL   ORGANISM. 


C9 


leeornpose  carbonic  acid,  and  to  assimilate 
the  elements  of  its  nourishment. 

In  the  flower  alone  does  a  process  similar 
to  the  change  of  matter  in  the  animal  body 
occur.  There,  phenomena  of  motion  ap- 
pear ;  but  the  mechanical  effects  are  not 
propagated  to  a  distance,  owing  to  the  ab- 
sence of  conductors  of  force. 

The  same  vital  force  which  we  recognize 
in  the  plant  as  an  almost  unlimited  capacity 
of  growth,  is  converted  in  the  animal  body 
into  moving  power  (into  a  current  of  vital 
force ;)  and  a  most  wonderful  and  wise  eco- 
nomy has  destined  for  the  nourishment  of 
the  animal  only  such  compounds  as  have  a 
composition  identical  with  that  of  the  organs 
which  generate  force,  that  is,  with  the  mus- 
cular tissue.  The  expenditure  of  force 
which  the  living  parts  of  animals  require, 
in  order  to  reproduce  themselves  from  the 
blood ;  the  resistance  of  the  chemical  force 
which  has  to  be  overcome  in  the  azotized 
constituents  of  food  by  the  vital  agency  of 
the  organs  destined  to  convert  them  into 
blood  ;  these  are  as  nothing  compared  to 
the  force  with  which  the  elements  of  carbo- 
nic acid  are  held  together.  A  certain  amount 
of  force  would  necessarily  be  prevented  from 
assuming  the  form  of  moving  power,  if  it 
were  to  be  expended  in  overcoming  chemical 
resistance  ;  for  the  momentum  of  motion  of 
the  vital  force  is  diminished  by  all  obstacles. 
But  the  conversion  of  the  constituents  of 
blood  into  muscular  fibre  (into  an  organ 
which  generates  force)  is  only  a  change  of 
form.  Both  have  the  same  composition; 
blood  is  fluid,  muscular  fibre  is  solid  blood. 
We  may  even  suppose  that  this  change 
takes  place  without  any  expenditure  of  vital 
force ;  for  the  mere  passage  of  a  fluid  body 
into  the  solid  state  requires  no  manifestation 
of  force,  but  only  the  removal  of  obstacles, 
which  oppose  that  force  (cohesion)  which 
determines  the  form  of  matter,  in  its  mani- 
festations. 

In  what  form  or  in  what  manner  the  vital 
force  produces  mechanical  effects  in  the  ani- 
mal body  Is  altogether  unknown,  and  is  as 
little  to  be  ascertained  by  experiment  as  the 
connexion  of  chemical  action  with  the  phe- 
nomena of  motion  which  we  can  produce 
with  the  galvanic  battery.  AH  the  explana- 
tions which  have  been  attempted  are  only 
representations  of  the  phenomenon;  they 
are,  more  or  less,  exact  descriptions  and 
comparisons  of  known  phenomena  with 
these,  whose  cause  is  unknown.  In  this  re- 
spect we  are  like  an  ignorant  man,  to  whom 
the  rise  and  fall  of  an  iron  rod  in  a  cylinder, 
in  which  the  eye  can  perceive  nothing,  and 
its  connexion  with  the  turning  and  motion 
of  a  thousand  wheels  at  a  distance  from  the 
piston-rod,  appear  incomprehensible. 

We  know  not  how  a  certain  something,  in- 
visible and  imponderable  in  itself  (heat)  gives 
to  certain  bodies  the  power  of  exerting  an 
enormous  pressure  on  surrounding  objects ; 
we  know  not  even  how  this  something  it- 
Be]  f  is  produced  when  we  burn  wood  or  coals. 


So  is  it  with  the  vital  force,  and  with  the 
phenomena  exhibited  by  living  bodies.  The 
cause  of  these  phenomena  is  not  chemical 
force ;  it  is  not  electricity,  nor  magnetism  \ 
it  is  a  force  which  has  certain  properties  in 
common  with  all  causes  of  motion  and  of 
hange  in  form  and  structure  in  material 
substances.  It  is  a  peculiar  force,  because 
it  exhibits  manifestations  which  are  found  in 
no  other  known  force. 

II.  In  the  living  plant,  the  intensity  of  the 
vital  force  far  exceeds  that  of  the  chemical 
action  of  oxygen. 

We  know,  with  the  utmost  certainty,  that 
by  the  influence  of  the  vital  force,  oxygen  is 
separated  from  elements  to  which  it  has  the 
strongest  affinity  ;  that  it  is  given  out  in  the 
gaseous  form,  without  exerting  the  slightest 
action  on  the  juices  of  the  plant. 

How  powerful,  indeed,  must  the  resistance 
appear  which  the  vital  force  supplies  to 
leaves  charged  with  oil  of  turpentine  or  tan- 
nic  acid,  when  we  consider  the  affinity  of 
oxygen  for  these  compounds ! 

This  intensity  of  action  or  of  resistance 
the  plant  obtains  by  means  of  the  sun's 
light ;  the  effect  of  which  in  chemical  ac- 
tions may  be,  and  is,  compared  to  that  of  a 
very  high  temperature  (moderate  red  heat.) 

During  the  night  an  opposite  process  goes 
on  in  the  plant ;  we  see  then  that  the  con- 
stituents of  the  leaves  and  green  parts  com- 
bine with  the  oxygen  of  the  air,  a  property 
which  in  daylight  they  did  not  possess. 

From  these  facts  we  can  draw  no  other 
conclusion  but  this  :  that  the  intensity  of  the 
vital  force  diminishes  with  the  abstraction 
of  light  5  that  with  the  approach  of  night  a 
state  of  equilibrium  is  established,  and  that 
in  complete  darkness  all  those  constituents 
of  plants  which,  during  the  day,  possessed 
the  power  of  separating  oxygen  from  chemi- 
cal combinations;  and  of  resisting  its  atruon, 
lose  their  power  completely. 

A  precisely  similar  phenomenon  is  ob- 
served in  animals. 

The  living  animal  body  exhibits  its  pecu- 
liar manifestations  of  vitality  only  at  certain 
temperatures.  When  exposed  to  a  certain 
degree  of  cold,  these  vital  phenomena  en- 
tirely cease. 

The  abstraction  of  heat  must,  therefore, 
be  viewed  as  quite  equivalent  to  a  diminu- 
tion of  the  vital  energy ;  the  resistance  op 
posed  by  the  vital  force  to  external  causes  of 
disturbance  must  diminish,  in  certain  tempe- 
ratures, in  the  same  ratio  in  which  the 
tendency  of  the  elements  of  the  body  to 
combine  with  the  oxygen  of  the  air  in- 
creases. 

By  the  combination  of  oxygen  with  the 
constituents  of  the  metamorphosed  tissues, 
the  temperature  necessary  to  the  manifesta- 
tions of  vitality  is  produced  in  the  carnivora. 
In  the  herbivora,  again,  a  certain  amount  of 
heat  is  developed  by  means  of  those  elements 
of  their  non-azotized  food  which  have  the 
property  of  combining  with  oxygen. 

It  is  obvious  that  the  temperature  of  an 


70 


ANIMAL   CHEMISTRY. 


animal  body  cannot  change,  if  the  amount 
of  inspired  oxygen  increases  in  the  same 
ratio  as  the  loss  of  heat  by  external  cooling. 

Two  individuals,  carnivora,  of  equal 
weight,  exposed  to  unequal  degrees  of  cold, 
lose,  in  a  given  time,  by  external  cooling, 
unequal  quantities  of  heat.  Experience 
teaches,  that  if  their  peculiar  temperature 
and  their  original  weight  are  to  remain  un- 
altered, they  require  unequal  quantities  of 
food  j  more  in  the  lower  temperature  than 
in  the  higher. 

The  circumstance  that  the  original  weight 
remains  the  same,  with  unequal  quantities 
of  food,  obviously  presupposes,  that  in  the 
same  time  a  quantity  of  oxygen  proportioned 
to  the  temperature  has  been  absorbed ;  more 
in  the  lower  than  in  the  higher  temperature. 

We  find  that  the  weight  of  both  indivi- 
duals, at  the  end  of  24  hours,  is  equal  to  the 
original  weight.  But  we  have  assumed 
that  their  food  is  converted  into  blood ;  that 
the  blood  has  served  for  nutrition ;  and  it  is 
plain,  that  when  the  original  weight  has 
been  restored,  a  quantity  of  the  constituents 
of  the  body,  equal  in  weight  to  those  of  the 
food,  has  lost  its  condition  of  life,  and  has 
been  expelled  in  combination  with  oxygen. 

The  one  individual,  which,  being  exposed 
to  the  lower  temperature,  consumed  more 
food,  has  also  absorbed  more  oxygen;  a 
greater  quantity  of  the  constituents  of  its 
body  has  been  separated  in  combination 
with  oxygen;  and,  in  consequence  of  this 
combination  with  oxygen,  a  greater  amount 
of  heat  has  been  liberated,  by  which  means 
the  'neat  abstracted  has  been  restored,  and 
tne  proper  temperature  of  the  body  kept  up. 

Consequently,  by  the  abstraction  of  heat, 
provided  there  be  a  full  supply  of  food  and 
free  access  of  oxygen,  the  change  of  matter 
must  be  accelerated;  and,  along  with  the 
augmented  transformation,  in  a  given  time, 
of  living  tissues,  a  greater  amount  of  vital 
force  must  be  rendered  available  for  mecha- 
nical purposes. 

With  the  external  cooling,  the  respiratory 
motions  become  stronger;  in  a  lower  tem- 
perature more  oxygen  is  conveyed  to  the 
blood ;  the  waste  of  matter  increases,  and  if 
the  supply  be  not  kept  in  equilibrium  with 
this  waste,  by  means  of  food,  the  tempera- 
ture of  the  body  gradually  sinks. 

But,  in  a  given  time,  an  unlimited  supply 
of  oxygen  cannot  be  introduced  into  the 
body ;  only  a  certain  amount  of  living  tissue 
can  lose  the  state  of  life,  and  only  a  limited 
amount  of  vital  force  can  be  manifested  in 
mechanical  phenomena.  It  is  only,  there- 
fore, when  the  cooling,  the  generation  of 
force,  and  the  absorption  of  oxygen  are  in 
equilibrium  together,  that  the  temperature 
of  the  body  can  remain  unchanged.  If  the 
loss  of  heat  by  cooling  go  beyond  a  certain 
point,  the  vital  phenomena  diminish  in  the 
same  ratio;  for  the  temperature  falls,  and 
the  temperature  must  be  considered  as  a 
uniform  condition  of  their  manifestation. 

Now  experience  teaches,  that  when  the 


temperature  of  the  body  sinks,  the  power  of 
the  limbs  to  produce  mechanical  effects  (or 
the  force  necessary  to  the  voluntary  motions) 
is  also  diminished.  The  condition  of  sleep 
ensues,  and  at  last  even  the  involuntary 
motions  (those  of  the  heart  and  intestines, 
for  example)  cease,  and  apparent  death -or 
syncope  supervenes. 

It  is  obvious  that  the-cause  of  the  genera- 
,tion  of  force,  namely,  the  change  of  matter, 
is  diminished,  because,  with  the  abstraction 
of  heat,  as  in  the  plant  by  abstraction  of 
light,  the  intensity  of  the  vital  force  di- 
minishes. It  is  also  obvious  that  the  mo- 
mentum of  force  in  a  living  part  depends 
on  its  proper  temperature;  exactly  as  the 
effect  of  a  falling  body  stands  in  a  fixed 
relation  to  certain  other  conditions ;  for  ex- 
ample, to  the  velocity  attained  in  falling. 

When  the  -temperature  sinks,  jthe  vital 
energy  diminishes ;  when  it  again  rises,  the 
momentum  of  force  in  the  living  parts 
appears  once  more  in  all  its  original  in 
tensity. 

The  production  of  force  for  mechanical 
purposes,  and  the  temperature  of  the  body, 
must,  consequently,  bear  a  fixed  relation  to 
the  amount  of  oxygen  which  can  be  absorbed 
in  a  given  time  by  the  animal  body. 

The  quantities  of  oxygen  which  a  whale 
and  a  carriers  horse  can  inspire  in  a  given 
time  are  very  unequal.  The  temperature, 
as  well  as  the  quantity  of  oxygen,  is  much 
greater  in  the  horse. 

The  force  exerted  by  a  whale,  when 
struck  with  the  harpoon,  his  body  being 
supported  by  the  surrounding  medium,  and 
the  force  exerted  by  a  carrier's  horse,  which 
carries  its  own  weight  and  a  'heavy  burden 
for  eight  or  ten  hours,  must  both  bear  the 
same  ratio  to  the  oxygen  consumed.  If  we 
take  into  consideration  the  time  during  which 
the  force  is  manifested,  it  is  obvious  that  the 
amount  of  force  developed  by  the  horse  is 
far  greater  than  in  the  case  of  the  whale. 

In  climbing  high  mountains,  where,  in 
consequence  of  the  respiration  of  a  highly 
rarefied  atmosphere,  much  less  oxygen  is 
conveyed  to  the  blood,  in  equal  times,  than 
in  valleys  or  at  the  level  of  the  sea,  the 
change  of  matter  diminishes  in  the  same 
ratio,  and  with  it  the  amount  of  force  avail- 
able for  mechanical  purposes.  For  the  most 
part,  drowsiness  and  want  of  force  for  me- 
chanical exertions  come  on ;  after  twenty  or 
thirty  steps,  fatigue  compels  us  to  a  fresh 
accumulation  offeree  by  means  of  rest  (ab- 
sorption of  oxygen  without  waste  of  force 
in  voluntary  motions.) 

By  the  absorption  of  oxygen  into  the  sub- 
stance of  living  tissues,  these  lose  their  con- 
dition of  life,  and  are  separated  as  lifeless, 
unorganized  compounds;  but  the  whole  of 
the  inspired  oxygen  is  not  applied  to  these 
transformations:  the  greater  part  serves  to 
convert  into  gas  and  vapour  all  matters 
which  no  longer  belong  to  the  organism; 
and,  as  formerly  mentioned,  the  combina- 
tion of  the  elements  of  such  compounds 


MOTION   IN   THE   ANIMAL    ORGANISM. 


71 


with  the  oxygen  produces  the  temperature 
proper  to  the  animal  organism. 

The  production  of  heat  and  the  change 
of  matter  are  closely  related  to  each  other : 
but  although  heat  can  be  produced  in  the 
body  without  any  change  of  matter  in  living 
tissues,  yet  the  change  of  matter  cannot  be 
supposed  to  take  place  without  the  co-opera- 
tion of  oxygen. 

According  to  all  the  observations  hitherto 
made,  neither  the  expired  air  nor  the  per- 
spiration, nor  the  urine,  contains  any  trace 
of  alcohol,  after  indulgence  in  spirituous 
liquors ;  and  there  can  be  no  doubt  that  the 
elements  of  alcohol  combine  with  oxygen 
in  the  body;  that  its  carbon  and  hydrogen 
are  given  off  as  carbonic  acid  and  water. 

The  oxygen  which  has  accomplished  this 
change  must  have  been  taken  from  the  arte- 
rial blood;  for  we  know  of  no  channel, 
save  the  circulation  of  the  blood,  by  which 
oxygen  can  penetrate  into  the  interior  of  the 
body. 

Owing  to  its  volatility,  and  the  ease  with 
which  its  vapour  permeates  animal  mem- 
branes and  tissues,  alcohol  can  spread 
throughout  the  body  in  all  directions. 

If  the  power  of  the  elements  of  alcohol 
to  combine  with  oxygen  were  not  greater 
than  that  of  the  compounds  formed  by  the 
change  of  matter,  or  that  of  the  substance 
of  living  tissues,  they  (the  elements  of  alco- 
hol) could  not  combine  with  oxygen  in  the 
body.  t 

It  is,  consequently,  obvious,  that  by  the 
use  of  alcohol  a  limit  must  rapidly  be  put 
to  the  change  of  matter  in  certain  parts  of 
the  body.  The  oxygen  of  the  arterial 
blood,  which,  in  the  absence  of  alcohol, 
would  have  combined  with  the  matter  of 
the  tissues,  or  with  that  formed  by  the  meta- 
morphosis of  these  tissues,  now  combines 
with  the  elements  of  alcohol.  The  arterial 
blood  becomes  venous,  without  the  substance 
of  the  muscles  having  taken  any  share  in 
the  transformation. 

Now  we  observe,  that  the  developement 
of  heat  in  the  body,  after  the  use  of  wine, 
increases  rather  than  diminishes,  without 
the  manifestation  of  a  corresponding  amount 
of  mechanical  force. 

A  moderate  quantity  of  wine,  in  women 
and  children  unaccustomed  to  its  use,  pro- 
duces, on  the  contrary,  a  diminution  of  the 
force  necessary  for  voluntary  motions. 
Weariness,  feebleness  in  the  limbs,  and 
drowsiness,  plainly  show  that  the  force 
available  for  mechanical  purposes,  in  other 
words,  the  change  of  matter,  has  been  di- 
minished. 

A  diminution  of  the  conducting  power 
of  the  nerves  of  voluntary  motion  may 
dc  jbtless  take  a  certain  share  in  producing 
these  symptoms;  but  this  must  be  alto- 
gether without  influence  on  the  sum  of 
available  force. 

What  the  conductors  of  voluntary  motion 
cannot  carry  away  for  effects  of  force,  must 
be  taken  up  by  the  nerves  of  involuntary 


motion,  and  conveyed  to  the  heart,  lungs, 
and  intestines.  In  this  case,  the  circulation 
will  appear  accelerated  at  the  expense  of 
the  force  available  for  voluntary  motion  j 
but,  as  was  before  remarked,  without  the 
production  of  a  greater  amount  of  mechani- 
cal force  by  the  process  of  oxidation  of  the 
alcohol. 

Finally,  we  observe,  in  hybernating  ani- 
mals, that,  during  their  winter  sleep,  the 
capacity  of  increase  in  mass  (one  of  the 
chief  manifestations  of  the  vital  force,) 
owing  to  the  absence  of  food,  is  entirely 
suppressed.  In  several,  apparent  death  oc- 
curs in  consequence  of  the  low  temperature 
and  of  the  diminution  qf  vital  energy  thus 
produced  ;  in  others,  the  involuntary  mo- 
tions continue,  and  the  animal  preserves  a 
temperature  independent  of  the  surrounding 
temperature.  The  respirations  go  on ;  oxy- 
gen, the  condition  which  determines  the 
production  of  heat  and  force,  is  absorbed 
now  as  well  as  in  the  former  state  of  the 
animal;  and  previous  to  the  winter  sleep, 
we  find  all  those  parts  of  their  body,  which 
in  themselves  are  unable  to  furnish  resist- 
ance to  the  action  of  the  oxygen,  and  which, 
like  the  intestines  and  membranes,  are  not 
destined  for  the  change  of  matter,  covered 
with  fat;  that  is,  surrounded  by  a  substance 
which  supplies  the  want  of  resistance. 

If  we  now  suppose,  that  the  oxygen  ab- 
sorbed during  the  winter  sleep  combines, 
not  with  the  elements  of  living  tissues,  but 
with  those  of  the  fat,  then  the  living  part, 
although  a  certain  momentum  of  motion  be 
expended  in  keeping  up  the  circulation,  will 
not  be  separated  and  expelled  from  the  body. 

With  the  return  of  the  higher  tempera- 
ture, the  capacity  of  growth  increases  in  the 
same  ratio,  and  the  motion  of  the  blood  in- 
creases with  the  absorption  of  oxygen. 
Many  of  these  animals  become  emaciated 
during  the  winter  sleep,  others  not  till  after 
awaking  from  it. 

In  hybernating  animals  the  active  force 
of  the  living  parts  is  exclusively  devoted, 
during  hybernation,  to  the  support  of  the  in- 
voluntary motions.  The  expenditure  of  force 
in  voluntary  motion  is  entirely  suppressed. 

In  contradistinction  to  these  phenomena, 
we  know  that,  in  the  case  of  excess  of  mo- 
tion and  exertion,  the  active  force  in  living 
parts  may  be  exclusively  and  entirely  con- 
sumed in  producing  voluntary  mechanical 
effects;  in  such  wise  that  no  force  shall  re- 
main available  for  the  involuntary  motions. 
A  stag  may  be  hunted  to  death ;  but  this 
cannot  occur  without  the  metamorphosis  of 
all  the  living  parts  of  its  muscular  system, 
and  its  flesh  becomes  uneatable.  The  con- 
dition of  metamorphosis  into  which  it  has 
been  brought  by  an  enormous  consumption 
both  of  force  and  of  oxygen  continues  when 
all  phenomena  of  motion  have  ceased.  In 
the  living  tissues,  all  the  resistance  offered 
by  the  vital  force  to  external  agencies  of 
change  is  entirely  destroyed. 

But  however  closely  the  conditions  of  the 


7-2 


ANIMAL   CHEMISTRY. 


production  of  heat  and  of  force  may  seem 
to  be  connected  together,  with  reference  to 
mechanical  effects,  yet  the  disengagement 
of  heat  can  in  no  way  be  considered  as  in 
itself  the  only  cause  of  these  effects. 

All  experience  proves,  that  there  is,  in 
the  organism,  only  one  source  of  mechani- 
cal power;  and  this  source  is  the  conversion 
of  living  parts  into  lifeless,  amorphous  com- 
pounds. 

Proceeding  from  this  truth,  which  is  inde- 
pendent of  all  theory,  animal  life  may  be 
/•iewed  as  determined  by  the  mutual  action 
of  opposed  forces;  of  which  one  class  must 
je  considered  as  causes  of  increase,  (of  sup- 
ply of  matter,)  and  the  other  as  causes  of 
Mminution  (of  waste  of  matter.) 

The  increase  of  mass  is  effected  in  living 
larts  by  the  vital  force;  the  manifestation 
3f  this  power  is  dependent  on  heat;  that  is, 
jn  a  certain  temperature  peculiar  to  each 
specific  organism. 

The  cause  of  waste  of  matter  is  the  chemi- 
cal action  of  oxygen  ;  and  its  manifestation 
is  dependent  on  the  abstraction  of  heat  as 
well  as  on  the  expenditure  of  the  vital  force 
"or  mechanical  purposes. 

The  act  of  waste  of  matter  is  called  the 
;hange  of  matter ;  it  occurs  in  consequence 
of  the  absorption  of  oxygen  into  the  sub- 
stance of  living  parts.  This  absorption  of 
oxygen  occurs  only  when  the  resistance 
which  the  vital  force  of  the  living  parts  op- 
poses to  the  chemical  action  of  the  oxygen 
is  weaker  than  that  chemical  action ;  and 
this  weaker  resistance  is  determined  by  the 
abstraction  of  heat,  or  by  the  expenditure  in 
mechanical  motions  of  the  available  force 
of  living  parts. 

By  the  combination  of  the  oxygen  intro- 
duced into  the  arterial  blood  with  such  con- 
stituents of  the  body  as  offer  no  resistance 
to  its  action,  the  temperature  necessary  for 
the  manifestation  of  vital  activity  is  pro- 
duced. 

From  the  relations  between  the  consump- 
tion of  oxygen  on  the  one  hand  and  the 
change  of  matter  and  developement  of  heat 
on  the  other,  the  following  general  rules  may 
be  deduced. 

For  every  proportion  of  oxygen  which 
enters  into  combination  in  the  body,  a  cor- 
responding proportion  of  heat  must  be  gene- 
rated. 

The  sum  of  force  available  for  mechanical 
purposes  must  be  equal  to  the  sum  of  vital 
forces  of  all  tissues  adapted  to  the  change 
of  matter. 

If,  in  equal  times,  unequal  quantities  of 
oxygen  are  consumed,  the  result  is  obvious, 
in  an  unequal  amount  of  heat  liberated,  and 
of  mechanical  force. 

When  unequal  amounts  of  mechanical 
force  are  expended,  this  determines  the  ab- 
sorption of  corresponding  and  unequal  quan- 
tities of  oxygen. 

For  the  conversion  of  living  tissues  into 
lifeless  compounds,  and  for  the  combination  ; 
of  oxygen   with  such   constituents  of  the  i 


body  as  have  an  affinity  for  it,  time  is  re- 
quired. 

In  a  given  time,  only  a  limited  amount  of 
mechanical  force  can  be  manifested,  and 
only  a  limited  amount  of  heat  can  be  libe- 
rated. 

That  which  is  expended,  in  mechanical 
effects,  in  the  shape  of  velocity,  is  lost  in 
time;  that  is  to  say,  the  more  rapid  the  mo- 
tions are,  the  sooner  or  the  more  quickly  is 
the  force  exhausted. 

The  sum  of  the  mechanical  force  pro- 
duced in  a  given  time  is  equal  to  the  sum  of 
force  necessary,  during  the  same  time,  to 
produce  the  voluntary  and  involuntary  mo- 
tions ;  that  is,  all  the  force  which  the  heart, 
intestines,  &,c.,  require  for  their  motions  is 
lost  to  the  voluntary  motions. 

The  amount  of  azotized  food  necessary  to 
restore  the  equilibrium  between  waste  and 
supply  is  directly  proportional  to  the  amount 
of  tissues  metamorphosed. 

The  amount  of  living  matter,  which  in 
the  body  loses  the  condition  of  life,  is,  in 
equal  temperatures,  directly  proportional  to 
the  mechanical  effects  produced  in  a  given 
time. 

The  amount  of  tissue  metamorphosed  in 
a  given  time  may  be  measured  by  the  quan- 
tity of  nitrogen  in  the  urine. 

The  sum  of  the  mechanical  effects  pro- 
duced in  two  individuals,  in  the  same  tem- 
perature, is  proportional  to  the  amount  of 
nitrogen  in  their  urine;  whether  the  mecha- 
nical force  has  been  employed  in  voluntary 
or  involuntary  motions,  whether  it  has  been 
consumed  by  the  limbs  or  by  the  heart  and 
other  viscera. 

That  condition  of  the  body  which  is  called 
health  includes  the  conception  of  an  equili- 
brium among  all  the  causes  of  waste  and 
of  supply;  and  thus  animal  life  is  recog- 
nized as  the  mutual  action  of  both;  and  ap- 
pears as  an  alternating  destruction  and  resto- 
ration of  the  state  of  equilibrium. 

In  regard  to  its  absolute  amount,  the  waste 
and  supply  of  matter  is,  in  the  different  pe- 
riods of  life,  unequal ;  but,  in  the  state  of 
health,  the  available  vital  force  must  always 
be  considered  as  a  constant  quantity,  corre- 
sponding to  the  sum  of  living  particles. 

Growth,  or  the  increase  of  mass,  stands, 
at  every  age,  in  a  fixed  relation  to  the 
amount  of  vital  force  consumed  as  moving 
power. 

The  vital  force,  which  is  expended  for 
mechanical  purposes,  is  subtracted  from  the 
sum  of  the  force  available  for  the  purpose 
of  increase  of  mass. 

The  active  force,  which  is  consumed  in 
the  body  in  overcoming  resistance  (in  caus- 
ing increase  of  mass)  cannot,  at  the  same 
time,  be  employed  to  produce  mechanical 
effects. 

Hence  it  follows  necessarily,  that  when, 
as  in  childhood,  the  supply  exceeds  the 
waste  of  matter,  the  mechanical  effects  pro- 
duced must  be  less  in  the  same  proportion. 

With  the  increase  of  mechanical  effects 


MOTION    IN    THE    ANIMAL    ORGANISM. 


produced,  the  capacity  of  increase  of  mass 
or  of  the  supply  of  waste  in  living  tissues 
must  diminish  in  the  same  proportion. 

A  perfect  balance  between  the  consump- 
tion of  vital  force  for  supply  of  matter  and 
that  for  mechanical  effects  occurs,  therefore, 
only  in  the  adult  slate.  It  is  at  once  recog- 
nized in  the  complete  supply  of  the  matter 
consumed.  In  old  age  more  is  wasted;  in- 
childhood  more  is  supplied  than  wasted. 

The  force  available  for  mechanical  pur- 
poses in  an  adult  man  is  reckoned,  in  me- 
chanics, equal  to  the  £th  of  his  own  weight, 
which  he  can  move  during  eight  hours, 
with  a  velocity  of  five  feet  in  two  seconds. 

If  the  weight  of  a  man  be  150  Ibs.,  his 
force  is  equal  to  a  weight  of  30  Ibs.  carried 
by  him  to  a  distance  of  72,000  feet.  For 
every  second  his  momentum  of  force  is 
=  30x2-5  =  75  Ibs.;  and  for  the  whole 
day's  work  his  momentum  of  motion  is 
=  30x72,000  =  216,000. 

By  the  restoration  of  the  original  weight 
of  his  body,  the  man  collects  again  a  sum 
offeree  which  allows  him,  next  day, to  pro- 
duce, without  exhaustion,  the  same  amount 
of  mechanical  effects. 

This  supply  of  force  is  furnished  in  a  seven 
hours'1  sleep. 

In  manufactories  of  rolled  iron  it  fre- 
quently happens,  that  the  pressure  of  the 
engine,  going  at  its  ordinary  rate,  is  not  suf- 
ficient to  force  a  rod  of  iron  of  a  certain 
thickness  to  pass  below  the  cylinders.  The 
workman,  in  this  case,  allows  the  whole 
force  of  the  steam  to  act  on  the  revolving 
wheel,  and  not  until  this  has  acquired  a 
great  velocity  does  he  bring  the  rod  under 
the  rollers ;  when  it  is  instantly  flattened  with 
great  ease  into  a  plate,  while  the  wheel  gra- 
dually loses  the  velocity  it  had  acquired. 
What  the  wheel  gained  in  velocity  the  roller 
gained  in  force ;  by  this  process  force  was 
obviously  collected,  accumulated  in  the  ve- 
locity ;  but  in  this  sense  force  does  not  ac- 
cumulate in  the  living  organism. 

The  restoration  of  force  is  effected,  in  the 
animal  body,  by  the  transformation  of  the 
separated  parts,  destined  for  the  production 
of  force,  and  by  the  expenditure  of  the  active 
vital  force  in  causing formation  of new  parts  ; 
and,  with  the  restoration  of  the  separated  or 
effete  parts,  the  organism  recovers  a  force 
equal  to  that  which  has  been  expended. 

It  is  plain,  that  the  vital  force  manifested, 
during  sleep,  in  the  formation  of  new  parts, 
must  be  equal  to  the  whole  sum  of  the  mov- 
ing power  expended  in  the  waking  state  in 
all  mechanical  effects  whatever,  plus  a  cer- 
tain amount  of  force,  which  is  required  for 
carrying  on  those  involuntary  motions  which 
continue  during  sleep. 

From  clay  to  day,  the  labouring  man,  with 
sufficient  food,  recovers,  in  seven  hours' 
sleep,  the  whole  sum  offeree;  and  without 
reckoning  the  force  necessary  for  the  invo- 
luntary motions  which  may  be  considered 
equal  in  all  men,  we  may  assume,  that  the 
mechanical  force  available  for  work  is  di- 
10 


rectly  proportional  to  the  number  of  hours 
of  sleep. 

The  adult  man  sleeps  7  hours,  and  wakes 
17  hours;  consequently,  if  the  equilibrium 
be  restored  in  24  hours,  the  mechanical  ef- 
fects produced  in  17  hours  must  be  equal  to 
the  effects  produced  during  7  hours  in  the 
shape  of  formation  of  new  parts. 

An  old  man  sleeps  only  3£  hours;  and  if 
every  thing  else  be  supposed  the  same  as  in 
the  case  of  the  adult,  he  will  be  able,  at  all 
events,  to  produce  half  of  the  mechanical 
effects  produced  by  an  adult  of  equal  weight; 
that  is,  he  will  be  able  to  carry  only  15  Ibs. 
instead  of  30  to  the  same  distance. 

The  infant  at  the  breast  sleeps  20  hours 
and  wakes  only  four ;  the  active  force  con- 
sumed in  formation  of  new  parts  is,  in  this 
case,  to  that  consumed  in  mechanical  effects 
(in  motion  of  the  limbs)  as  20  to  4;  but  his 
limbs  possess  no  momentum  of  force,  for  he 
cannot  yet  support  his  own  body.  If  we 
assume,  that  the  aged  man  and  infant  con- 
sume in  mechanical  effects  a  quantity  of 
force  corresponding  to  the  proportion  avail 
able  in  the  adult,  then  the  mechanical  effects 
are  proportional  to  the  number  of  waking 
hours,  the  formation  of  new  parts  to  the 
number  of  hours  of  sleep,  and  we  shall  have : 
Force  expended  in  Force  expended  in 
mechanical  effects,  formation  of  new  parts. 


In  the  adult 
In  the  infant . 
In  the  old  man 


17 
4 

20 


7 
20 
4 


In  the  adult  a  perfect  equilibrium  takes 
place  between  waste  and  supply;  in  the  old 
man  and  in  the  infant,  waste  and  supply  are 
not  in  equilibrium.  If  we  make  the  con- 
sumption of  force  in  the  17  waking  hours 
equal  to  that  required  for  the  restoration  of 
the  equilibrium  during  sleep  =  100  =  17 
waking  hours,  =  7  hours  of  sleep,  we  obtain 
the  following  proportions.  The  mechanical 
effects  are  to  those  in  the  shape  of  formation 
of  new  parts : 

In  the  adult  man  =  100  :  100 
In  the  infant  .  .    =  25  :  250 
In  the  old  man  .    =  125  :    50 
Or  the  increase  of  mass  to  the  diminution 
by  waste : 

In  the  adult  man  =  100  :  100 
In  the  infant  .  .   =  100  :    10 
In  the  old  man  .   =  100  :  250 
It  is  consequently  clear,  that  if  the  old 
man  performs  an  amount  of  work  propor- 
tional to  the  sleeping  hours  of  the  adult,  the 
waste  will  be  greater  than  the  supply ;  that 
is,  his  body  will  rapidly  decrease  in  weight, 
if  he  carry  15  Ibs.  to  the  distance  of  72,000 
feet  with  a  velocity  of  24  feet  in  the  second  ; 
but  he  will  be  able,  without  injury,  to  carry 
6  Ibs.  to  the  same  distance. 

In  the  infant  the  increase  is  to  the  decrease 
as  10  to  1,  and  consequently,  if  we  in  his 
case  increase  the  expenditure  of  force  in 
mechanical  effects  to  ten  times  its  proper 
amount,  there  will  thus  be  established  only 
an  equilibrium  between  waste  and  supply 
G 


74 


ANIMAL   CHEMISTRY. 


The  child,  indeed,  will  not  grow,  but  neither 
will  it  lose  weight. 

II,  in  the  adult  man,  the  consumption  of 
force  for  mechanical  purposes  in  24  hours 
be  augmented  beyond  the  amount  restorable 
in  seven  hours  of  sleep,  then,  if  the  equili- 
brium is  to  be  restored,  less  force,  in  the 
same  proportion,  must  be  expended  in  me- 
chanical effects  in  the  next  24  hours.  If 
this  be  not  done,  the  mass  of  the  body  de- 
creases, and  the  state  characteristic  of  old 
age  more  or  less  decidedly  supervenes. 

With  every  hour  of  sleep  the  sum  of  avail- 
able force  increases  in  the  old  man,  or  ap- 
proaches the  state  of  equilibrium  between 
waste  and  supply  which  exists  in  the  adult. 

It  is  further  evident,  that  if  a  part  of  the 
forte  which  is  available  for  mechanical 
purposes,  without  disturbing  the  equilibrium, 
should  not  be  consumed  in  moving  the 
limbs,  in  raising  weights,  or  in  other  labour, 
it  will  be  available  for  involuntary  motions. 
If  the  motion  of  the  heart,  of  the  fluids,  and 
of  the  intestines  (the  circulation  of  the  blood 
and  digestion)  are  accelerated  in  proportion 
to  the  amount  of  force  not  consumed  in 
voluntary  motions,  the  weight  of  the  body 
will  neither  increase  or  diminish  in  24  hours. 
The  body,  therefore,  can  only  increase  in 
mass,  if  the  force  accumulated  during  sleep, 
and  available  for  mechanical  purposes,  is 
employed  neither  for  voluntary  nor  for  in- 
roluntary  motions. 

The  numerical  values  above  given  for 
the  expenditure  of  force  in  the  human  body 
refer,  as  has  been  expressly  stated,  only  to  a 
given,  uniform  temperature.  In  a  different 
temperature,  and  with  deficient  nourishment, 
all  these  proportions  must  be  changed. 

If  we  surround  a  part  of  the  body  with  ice 
or  snow,  while  other  parts  are  left  in  the 
natural  state,  there  occurs,  more  or  less 
quickly,  in  consequence  of  the  loss  of 
heat,  an  accelerated  change  of  matter  in 
the  cooled  part. 

The  resistance  of  the  living  tissues  to  the 
action  ,of  oxygen  is  weaker  at  the  cooled 
part  than  in  the  other  parts ;  and  this,  in  its 
effects,  is  equivalent  to  an  increase  of  re- 
sistance in  these  other  parts. 

The  momentum  of  force  of  the  vitality  in 
the  parts  which  are  not  cooled  is  expended , 
as  before,  in  mechanical  motion ;  but  the 
whole  action  of  the  inspired  oxygen  is 
exerted  on  the  cooled  part. 

If  we  imagine  an  iron  cylinder,  into 
which  we  admit  steam  under  a  certain 
pressure,  then  if  the  force  with  which  the 
particles  of  the  iron  cohere  be  equal  to  the 
force  which  tends  to  separate  them,  an  equi- 
librium will  result ;  that  is,  the  whole  effect 
of  the  steam  will  be  neutralized  by  the  re- 
sistance. But  if  one  of  the  sides  of  the 
cylinder  be  moveable,  a  piston-rod,  for  ex- 
ample, and  offer  to  the  pressure  of  the  steam 
a  less  resistance  than  other  parts,  the  whole 
force  will  be  expended  in  moving  this  one 
side — that  is,  in  raising  the  piston-rod.  If 
we  do  not  introduce  fresh  steam  (fresh  force) 


an  equilibrium  will  soon  be  established.  The 
piston-i  od  resists  a  certain  force  without 
moving,  but  is  raised  by  an  increased  pres- 
sure. When  this  excess  of  force  has  been 
consumed  in  motion,  it  cannot  be  raised 
higher;  but  if  new  vapour  be  continually 
admitted,  the  rod  will  continue  to  move. 

In  the  cooled  part  of  the  body,  the  living 
tissues  offer  a  less  resistance  to  the  chemical 
action  of  the  inspired  oxygen ;  the  power 
of  the  oxygen  to  unite  with  the  elements  of 
the  tissues  is,  at  this  part,  exalted.  When 
the  part  has  once  lost  its  condition  of  life, 
resistance  entirely  ceases;  and  in  conse- 
quence of  the  combination  of  the  oxygen 
with  the  elements  of  the  metamorphosed 
tissues,  a  greater  amount  of  heat  is  liberated. 

Eor  a  given  amount  of  oxygen,  the  heat 
produced  is,  in  all  cases,  exactly  the  same. 
In  the  cooled  part,  the  change  of  matter, 
and  with  it  the  disengagement  of  heat,  in- 
creases ;  while  in  the  other  parts  the  change 
of  matter  and  liberation  of  heat  decrease. 
But  when  the  cooled  part,  by  the  union  of 
oxygea  with  the  elements  of  the  metamor- 
phosed tissues,  has  recovered  its  original 
temperature,  the  resistance  of  its  living  par- 
ticles to  the  oxygen  conveyed  to  them  again 
increases,  and,  as  the  resistance  of  other 
parts  is  now  diminished,  a  more  rapid 
change  of  matter  now  occurs  in  them,  their 
temperature  rises,  and  along  with  this,  if  the 
cause  of  the  change  of  matter  continues  to 
operate,  a  larger  amount  of  vital  force  be- 
comes available  for  mechanical  purposes. 

Let  us  now  suppose  that  heat  is  abstracted 
from  the  whole  surface  of  the  body ;  in  this 
case  the  whole  action  of  the  oxygen  will  be 
directed  to  the  skin,  and  in  a  short  time  the 
change  of  matter  must  increase  throughout 
the  body.  Fat,  and  all  such  matters  as  are 
capable  of  combining  with  the  oxygen 
which  is  brought  to  them  in  larger  quantity 
than  usual,  will  be  expelled  from  the  body 
in  the  form  of  oxidized  compounds. 

III. — THEORY  OF  DISEASE.  Every  sub- 
stance or  matter,  every  chemical  or  mecha- 
nical agency,  which  changes  or  disturbs  the 
restoration  of  the  equilibrium  between  the 
manifestations  of  the  causes  of  waste  and 
supply,  in  such  a  way  as  to  add  its  action 
to  the  causes  of  waste,  is  called  a  cause  of 
disease.  Disease  occurs  when  the  sum  of 
vital  force,  which  tends  to  neutralize  all 
causes  of  disturbance,  (in  other  words,  when 
the  resistance  offered  oy  the  vital  force,)  is 
weaker  than  the  acting  cause  of  disturbance. 

Death  is  that  condition  in  which  all  resist- 
ance on  the  part  of  the  vital  force  entirely 
ceases.  So  long  as  this  condition  is  not  es- 
tablished, the  living  tissues  continue  to  offer 
resistance. 

To  the  observer,  the  action  of  a  cause  of 
disease  exhibits  itself  in  the  disturbance  of 
the  proportion  between  waste  and  supply 
which  is  proper  to  each  period  of  life.  In 
medicine,  every  abnorma  condition  of  sup- 
ply or  of  waste,  in  all  pai  ts  or  in  a  single 
part  of  the  body,  is  called  disease. 


THEORY   OF    DISEASE. 


75 


It  is  evident  that  3ue  and  the  same  cause 
of  disease  will  produce  in  the  organism  very 
different  effects,  according  to  the  period  of 
life ;  and  that  a  certain  amount  of  disturb- 
ance, which  produces  disease  in  the  adult 
state,  may  be  without  influence  in  childhood 
or  in  old  age.  A  cause  of  disease  may, 
when  it  is  added  to  the  cause  of  waste  in  old 
age,  produce  death  (annihilate  all  resistance 
on  the  part  of  the  vital  force ;)  while  in  the 
adult  slate  it  may  produce  only  a  dispropor- 
tion between  supply  and  waste ;  and  in  in- 
fancy, only  an  equilibrium  between  supply 
and  waste  (the  abstract  state  of  health.) 

A  cause  of  disease  which  strengthens  the 
causes  of  supply,  either  directly  or  indirectly 
by  weakening  trie  action  of  the  causes  of 
waste,  destroys,  in  the  child  and  in  the 
adult,  the  relative  normal  state  of  health ; 
while  in  old  age  it  merely  brings  the  waste 
and  supply  into  equilibrium. 

A  child,  lightly  clothed,  can  bear  cooling 
by  a  low  external  temperature  without  in- 
jury to  health ;  the  force  available  for  me- 
chanical purposes  and  the  temperature  of 
its  body  increases  with  the  change  of  matter 
which  follows  the  cooling ;  while  a  higher 
temperature,  which  impedes  the  change  of 
matter,  is  followed  by  disease. 

On  the  other  hand,  we  see,  in  hospitals 
and  charitable  institutions  (in  Brussels,  for 
example)  in  which  old  people  spend  the  last 
years  of  life,  when  the  temperature  of  the  dor- 
mitory in  winter  sinks  2  or  3  degrees  below 
the  usual  point,  that  by  this  slight  degree  of 
cooling  the  death  of  trie  oldest  and  weakest 
males  as  well  as  females  is  brought  about. 
They  are  found  lying  tranquilly  in  bed, 
without  the  slightest  symptoms  of  disease, 
or  of  the  usual  recognizable  causes  of  death. 

A  deficiency  of  resistance,  in  a  living 
part,  to  the  cause  of  waste  is,  obviously,  a 
deficiency  of  resistance  to  the  action  of  the 
oxygen  of  the  atmosphere. 

When,  from  any  cause  whatever,  this  re- 
sistance diminishes  in  a  living  part,  the 
change  of  matter  increases  in  an  equal  de- 
gree. 

Now,  since  the  phenomena  of  motion  in 
the  animal  body  are  dependent  on  the 
change  of  matter,  the  increase  of  the  change 
of  matter  in  any  part  is  followed  by  an  in- 
crease of  all  motions.  According  to  the  con- 
ducting power  of  the  nerves,  the  available 
force  is  carried  away  by  the  nerves  of  invo- 
luntary motion  alone,  or  by  all  the  nerves 
together. 

Consequently,  if,  in  consequence  of  a  dis- 
eased transformation  of  living  tissues,  a 
greater  amount  of  force  be  generated  than  is 
required  for  the  production  of  the  normal 
motions,  it  is  seen  in  an  acceleration  of  all  or 
some  of  the  involuntary  motions,  as  well  as 
in  a  higher  temperature  of  the  diseased  part. 

This  condition  is  called  fever. 

When  a  great  excess  of  force  is  produced 
bv  change  of  matter,  the  force,  since  it  can 
only  be  consumed  by  motion,  extends  itself 
to  the  apparatus  of  voluntary  rnctioa. 


This  state  is  called  a  febrile  paroxysm. 

In  consequence  of  the  acceleration  of  the 
circulation  in  the  state  of  fever,  a  greater 
amount  of  arterial  blood,  and,  consequently 
of  oxygen,  is  conveyed  to  the  diseased  part, 
as  well  as  to  all  other  parts ;  and  if  the  ac- 
tive force  in  the  healthy  parts  continue  uni- 
form, the  whole  action  of  the  excess  of  oxy- 
gen must  be  exerted  on  the  diseased  part 
alone. 

According  as  a  single  organ,  or  a  system 
of  organs,  is  affected,  the  change  of  matter 
extends  to  one  part  alone,  or  to  the  whole 
affected  system. 

Should  there  be  formed,  in  the  diseased 
parts,  in  consequence  of  the  change  of  mat- 
ter, from  the  elements  of  the  blood  or  of  the 
tissue,  new  products,  which  the  neighbour- 
ing parts  cannot  employ  for  their  own  vital 
functions; — should  the  surrounding  parts, 
moreover,  be  unable  to  convey  these  pro- 
ducts to  other  parts,  where  they  may  un- 
dergo transformation,  then  these  new  pro- 
ducts will  suffer,  at  the  place  where  they 
have  been  formed,  a  process  of  decomposi- 
tion analogous  to  fermentation  or  putre- 
faction. 

In  certain  cases,  medicine  removes  these 
diseased  conditions,  by  exciting  in  the  vi- 
cinity of  the  diseased  part,  or  in  any  con- 
venient situation,  an  artificial  diseased  state 
(as  by  blisters,  sinapisms,  or  setons)  ;  thus 
aiminishing,  by  means  of  artificial  distur- 
bance, the  resistance  offered  to  the  external 
causes  of  change  in  these  parts  by  the  vital 
force.  The  physician  succeeds  in  putting 
an  end  to  the  original  diseased  condition, 
when  the  disturbance  artificially  excited  (or 
the  diminution  of  resistance  in  another  part) 
exceeds  in  amount  the  diseased  state  to  be 
overcome. 

The  accelerated  change  of  matter  and  the 
elevated  temperature  in  the  diseased  part 
show,  that  the  resistance  offered  by  the  vital 
force  to  the  action  of  oxygen  is  feebler  than 
in  the  healthy  state.  But  this  resistance 
only  ceases  entirely  when  death  takes  place. 
By  the  artificial  diminution  of  resistance  in 
another  part,  the  resistance  in  the  diseased 
organ  is  not  indeed  directly  strengthened  j 
but  the  chemical  action  (the  cause  of  the 
change  of  matter)  is  diminished  in  the 
diseased  part,  being  directed  to  another  part, 
where  the  physician  has  succeeded  in  pro- 
ducing a  still  more  feeble  resistance  to  the 
change  of  matter  (to  the  action  of  oxygen). 

A  complete  cure  of  the  original  disease 
occurs,  when  external  action  and  resistance, 
in  the  diseased  part,  are  brought  into  equili- 
brium. Health  and  the  restoration  of  the 
diseased  tissue  to  its  original  condition  fol- 
low, when  we  are  able  so  far  to  weaken  the 
disturbing  action  of  oxygen,  by  any  means, 
that  it  becomes  inferior  to  the  resistance  of- 
fered by  the  vital  force,  which,  although 
enfeebled,  has  never  ceased  to  act  j  for  this  ' 
proportion  between  these  causes  of  change 
is  the  uniform  and  necessary  conditicn  of 
increase  of  mass  in  the  living  organism. 


76 


ANIMAL   CHEMISTRY. 


In  cases  of  a  different  kind,  where  artifi- 
cial external  disturbance  produces  no  effect, 
the  physician  adopts  other  indirect  methods 
to  exalt  the  resistance  offered  by  the  vital 
force.  These  methods,  the  result  of  ages 
of  experience,  are  such,  that  the  most  per- 
fect theory  could  hardly  have  pointed  them 
out  more  acutely  or  more  justly  than  has 
been  done  by  the  observation  of  sagacious 
practitioners.  He  diminishes,  by  blood- 
letting, the  number  of  the  carriers  of  oxy- 
gen, (the  globules,)  and  by  this  means  the 
conditions  of  change  of  matter ;  he  excludes 
from  the  food  all  such  matters  as  are  capa- 
ble of  conversion  into  blood ;  he  gives 
chiefly  or  entirely  non-azotized  food,  which 
supports  the  respiratory  process,  as  well 
as  fruit  and  vegetables,  which  contain  the 
alkalies  necessary  for  the  secretions. 

If  he  succeed,  by  these  means,  in  dimi- 
nishing the  action  of  the  oxygen  in  the  blood 
on  the  diseased  part,  so  far  that  the  vital 
force  of  the  latter,  its  resistance,  in  the 
smallest  degree  overcomes  the  chemical  ac- 
tion ;  and  if  he  accomplish  this,  without  ar- 
resting the  functions  of  the  other  organs, 
then  restoration  to  health  is  certain. 

To  the  method  of  cure  adopted  in  such 
cases,  if  employed  with  sagacity  and  acute 
observation,  there  is  added,  as  we  may  call 
it,  an  ally  on  the  side  of  the  diseased  organ, 
and  this  is  the  vital  force  of  the  healthy 
parts.  For,  when  blood  is  abstracted,  the 
external  causes  of  change  are  diminished 
also  in  them,  and  their  vital  force,  formerly 
neutralized  by  these  causes,  now  obtains  the 
preponderance.  The  change  of  matter,  in- 
desd,  is  diminished  throughout  the  body, 
and  with  it  the  phenomena  of  motion  :  but 
the  sum  of  all  resisting  powers,  taken  to- 
gether, increases  in  proportion  as  the 
amount  of  the  oxygen  acting  on  them  in  the 
blood  is  diminished.  In  the  sensation  of 
hunger,  this  resistance,  in  a  certain  sense, 
makes  itself  known ;  and  the  preponderating 
vital  force  exhibits  itself,  in  many  patients, 
when  hunger  is  felt,  in  the  form  of  an  ab- 
normal growth,  or  in  abnormal  metamor- 
phosis of  certain  parts  of  organs,  Sympar- 
thy  is  the  transference  of  diminished  resist- 
ance from  one  part,  not  exactly  to  the  next, 
but  to  more  distant  organs,  when  the  func- 
tions of  both  mutually  influence  each  other. 
When  the  action  of  the  diseased  organ  is 
connected  with  that  of  another — when,  for 
example,  the  one  no  longer  produces  the 
matters  necessary  to  the  performance  of  the 
functions  of  the  other — then  the  diseased 
condition  is  transferred,  but  only  apparently, 
to  the  latter. 

In  regard  to  the  nature  and  essence  of  the 
vital  force,  we  can  hardly  deceive  ourselves, 
when  we  reflect,  that  it  behaves,  in  all  its 
manifestations,  exactly  like  other  natural 
forces ;  that  it  is  devoid  of  consciousness  or 
of  volition,  and  is  subject  to  the  action  of  a 
blister. 

The  nerves,  which  accomplish  the  volun- 
tary and  involuntary  motions  in  the  body,  ! 


'  are,  according  to  the  preceding  exposition, 
not  the  producers,  but  only  the  conductors 
of  the  vital  force ;  they  propagate  motion, 
and  behave  towards  other  causes  of  motion, 
which  in  their  manifestations  are  analogous 
to  the  vital  force,  towards  a  current  of  elec- 
tricity, for  example,  in  a  precisely  analo- 
gous manner.  They  permit  the  current  to 
traverse  them,  and  present,  as  conductors 
of  electricity,  ail  the  phenomena  which  they 
exhibit  as  conductors  of  the  vital  force.  In 
the  present  state  of  our  knowledge,  no  one, 
probably,  will  imagine  that  electricity  is  to 
be  considered  as  the  cause  of  the  phenomena 
of  motion  in  the  body ;  but  still,  the  medi- 
cinal action  of  electricity,  as  well  as  that  of 
a  magnet,  which,  when  placed  in  contact 
with  the  body,  produces  a  current  of  elec- 
tricity, cannot  be  denied.  For  to  the  ex- 
isting force  of  motion  or  of  disturbance  there 
is  added,  in  the  electrical  current,  a  new 
cause  of  motion  and  of  change  in  form  and 
structure,  which  cannot  be  considered  as  al- 
together inefficient. 

Practical  medicine,  in  many  diseases, 
makes  use  of  cold  in  a  highly  rational  man- 
ner, as  a  means  of  exalting  and  accelerating, 
in  an  unwonted  degree,  the  change  of  matter. 
This  occurs  especially  in  certain  morbid  con- 
ditions in  the  substance  of  the  centre  of  the 
apparatus  of  motion  5  when  a  glowing  heat 
and  a  rapid  current  of  blood  towards  the 
head  point  out  an  abnormal  metamorphosis 
of  the  brain.  When  this  condition  continues 
beyond  a  certain  time,  experience  teaches 
that  all  motions  in  the  body  cease.  If  the 
change  of  matter  be  chiefly  confined  to  the 
brain,  then  the  change  of  matter,  the  gene- 
ration of  force,  diminishes  in  all  other  parts. 
By  surrounding  the  head  with  ice,  the  tem- 
perature is  lowered,  but  the  cause  of  the 
liberation  of  heat  continues ;  the  metamor- 
phdsis,  which  decides  the  issue  of  the  dis- 
ease, is  limited  to  a  short  period.  We  must 
not  forget,  that  the  ice  melts  and  absorbs 
heat  from  the  diseased  part ;  that  if  the  ice 
be  removed  before  the  completion  of  the 
metamorphosis,  the  temperature  again  rises ; 
that  far  more  heat  is  removed  by  means  of 
ice  than  if  we  were  to  surround  the  head 
with  a  bad  conductor  of  heat.  There  has 
obviously  been  liberated  in  an  equal  time  «* 
far  larger  amount  of  heat  than  in  the  state 
of  health ;  and  this  is  only  rendered  possible 
by  an  increased  supply  of  oxygen,  which 
must  have  determined  a  more  rapid  change 
of  matter. 

The  self-regulating  steam  engines,  in 
which,  to  produce  a  uniform  motion,  the 
human  intellect  has  shown  the  most  ad- 
mirable acuteness  and  sagacity,  furnish  no 
unapt  image  of  what  occurs  in  the  animal 
body. 

Every  one  knows,  that  in  the  tube  which 
conveys  the  steam  to  the  cylinder  where  the 
piston-rod  is  to  be  raised,  a  stop-cock  oi 
peculiar  construction  is  placed,  through 
which  all  the  steam  must  pass.  By  an  ar- 
rangement connected  with  the  regulating 


THEORY    OF   RESPIRATION. 


77 


wheel,  this  stop-cock  opens  when  the  whee 
moves  slower,  and  closes  more  or  less  com- 
pletely when  the  wheel  moves  faster  than  is 
required  for  a  uniform  motion.  When  i 
opens,  more  steam  is  admitted,  (more  force,^ 
and  the  motion  of  the  machine  is  accele- 
rated. When  it  shuts,  the  steam  is  more  or 
less  cut  off,  the  force  acting  on  the  piston- 
rod  diminishes,  the  tension  of  the  steam  in- 
creases, and  this  tension  is  accumulated  for 
subsequent  use.  The  tension  of  the  vapour, 
ojr  the  force,  so  to  speak,  is  produced  by 
change  of  matter,  by  the  combustion  of 
coals  in  the  fire-place.  The  force  increases 
(the  amount  of  steam  generated  and  its  ten- 
sion increase)  with  the  temperature  in  the 
fire-place,  which  depends  on  the  supply  of 
coals  and  of  air.  There  are  in  these  engines 
other  arrangements,  all  intended  for  regula- 
tion. When  the  tension  of  steam  in  the 
boiler  rises  beyond  a  certain  point,  the  pas- 
sages for  admission  of  air  close  themselves; 
the  combustion  is  retarded,  the  supply  of 
force  (of  steam)  is  diminished.  When  the 
engine  goes  slower,  more  steam  is  admitted 
to  the  cylinder,  its  tension  diminishes,  the 
air  passages  are  opened,  and  the  cause  of 
disengagement  of  heat  (or  production  of 
force)  increases.  Another  arrangement  sup- 
plies the  fire-place  incessantly  with  coals  in 
proportion  as  they  are  wanted. 

If  we  now  lower  the  temperature  at  any 
part  of  the  boiler,  the  tension  within  is  di- 
minished; this  is  immediately  seen  in  the 
regulators  of  force,  which  act  precisely  as 
if  we  had  removed  from  the  boiler  a  certain 
quantity  of  steam  (force.)  The  regulator 
and  the  air-passages  open,  and  the  machine 
supplies  itself  with  more  coals. 

The  body,  in  regard  to  the  production  of 
heat  and  offeree,  acts  just  like  one  of  these 
machines.  With  the  lowering  of  the  ex- 
ternal temperature,  the  respirations  become 
deeper  and  more  frequent;  oxygen  is  sup- 
plied in  greater  quantity  and  of  greater  den- 
sity; the  change  of  matter  is  increased,  and 
more  food  must  be  supplied,  if  the  tempera- 
ture of  the  body  is  to  remain  unchanged. 

It  is  hardly  necessary  to  mention,  that  in 
the  body  the  tension  of  vapour  cannot,  any 
more  than  an  electrical  current,  be  consi- 
dered the  cause  of  the  production  offeree. 

From  the  theory  of  disease  developed  in 
the  preceding  pages,  it  follows  obviously, 
that  a  deceased  condition  once  established, 
in  any  part  of  the  body,  cannot  be  made  to 
disappear  by  the  chemical  action  of  a  re- 
medy. A  limit  may  be  put  by  a  remedy 
to  an  abnormal  process  of  transformation; 
th^t  process  may  be  accelerated  or  retarded; 
but  this  alone  does  not  restore  the  normal 
(healthy)  condition. 

The  art  of  the  physician  consists  in  the 
knowledge  of  the  means  which  enable  him 
to  exercise  an  influence  on  the  duration  of  i 
the  disease ;  and  in  the  removal  of  all  disturb- 
ing  causes,  the  action  of  which  strengthens  | 
or  increases   that  of  the  actual  cause  of  i 
disease. 


It  is  only  by  a  just  application  of  ite  prin- 
ciples that  any  theory  can  produce  really 
beneficial  results.  The  very  same  method 
of  cure  may  restore  health  in  one  individual, 
which,  if  applied  to  another,  may  prove  fatal 
in  its  effects.  Thus  in  certain  inflammatory 
diseases,  and  in  highly  muscular  subjects, 
the  antiphlogistic  treatment  has  a  very  high 
value;  while  in  other  cases  blood-letting 
produces  unfavourable  results.  The  vivify- 
ing agency  of  the  blood  must  ever  continue 
to  be  the  most  important  condition  in  the 
restoration  of  a  disturbed  equilibrium,  which 
result  is  always  dependent  on  the  saving  of 
time ;  and  the  blood  must,  therefore,  be  con- 
sidered and  constantly  kept  in  view,  as  the 
ultimate  and  most  powerful  cause  of  a  last- 
ing vital  resistance,  as  well  in  the  diseased 
as  in  the  unaffected  parts  of  the  body. 

It  is  obvious,  moreover,  that  in  all  dis- 
eases where  the  formation  of  contagious 
matter  and  of  exanthemata  is  accompanied 
by  fever,  two  diseased  conditions  simulta- 
neously exist,  and  two  processes  are  simul- 
taneously completed  ;  and  that  the  blood,  as 
it  were  by  re-action  (i.  e.  fever)  becomes  a 
means  of  cure,  as  being  the  carrier  of  that 
substance  (oxygen)  without  the  aid  of  which 
the  diseased  products  cannot  be  rendered 
harmless,  destroyed,  or  expelled  from  the 
body;  a  means  of  cure  by  which,  in  short, 
neutralization  or  equilibrium  is  effected. 

IV.  THEORY  OF  RESPIRATION. — During 
the  passage  of  the  venous  blood  through 
the  lungs,  the  globules  change  their  colour; 
and  with  this  change  of  colour,  oxygen  is 
absorbed  from  the  atmosphere.  Further 
or  every  volume  of  oxygen  absorbed,  an 
equal  volume  of  carbonic  acid  is,  in  mosi 
cases,  given  out. 

The  red  globules  contain  a  compound  of 
ron;  and  no  other  constituent  of  the  body 
contains  iron. 

Whatever  change  the  other  constituents 
of  the  blood  undergo  in  the  lungs,  thus 
much  is  certain,  that  the  globules  of  venous 
)lood  experience  a  change  of  colour,  and 
hat  this  change  depends  on  the  action  of 
oxygen. 

Now  we  observe  that  the  globules  of  arte- 
rial blood  retain  their  colour  in  the  larger 
vessels,  and  lose  it  only  during  their  pas- 
sage through  the  capillaries.  All  those  con- 
stituents of  venous  blood,  which  are  capable 
of  combining  with  oxygen,  take  up  a  cor- 
responding quantity  of  it  in  the  lungs.  Ex- 
>eriments  made  with  arterial  serum  have 
shown,  that  when  in  contact  with  oxygen 
it  does  not  diminish  the  volume  of  that  gas. 
Venous  blood,  in  contact  with  oxygen,  is 
reddened,  while  oxygen  is  absorbed;  and  a 
corresponding  quantity  of  carbonic  acid  is 
formed. 

It  is  evident  that  the  change  of  colour  in 
the  venous  globules  depends  on  the  combi- 
nation of  some  one  of  their  elements  with 
oxygen ;  and  that  this  absorption  of  oxygen 
is  attended  with  the  separation  of  a  certain 
quantity  of  carbonic  acid  gas. 

G* 


78 


ANIMAL   CHEMISTRY. 


This  carbonic  acid  is  not  separated  from 
the  serum;  for  the  serum  does  not  possess 
the  property,  when  in  contact  with  oxygen, 
of  giving  off  carbonic  acid.  On  the  con- 
trary, when  separated  from  the  globules,  it 
absorbs  fro-ii  naif  its  volume  to  an  equal 
volume  of  carbonic  acid,  and,  at  ordinary 
temperatures,  is  not  saturated  with  that  gas. 
(See  the  article  "  Blut,"  in  the  "  Handwor- 
terbuch  der  Chemie,  von  Poggendorff,  Wuh- 
ler,  und  Liebig,  p.  877.) 

Arterial  blood,  when  drawn  from  the 
body,  is  soon  altered ;  its  florid  colour  be- 
comes dark  red.  The  florid  blood,  which 
owes  its  colour  to  the  globules,  becomes 
dark  by  the  action  of  carbonic  acid,  and  this 
change  of  colour  affects  the  globules,  for 
florid  blood  absorbs  a  number  of  gases  which 
do  not  dissolve  in  the  fluid  part  of  the  blood 
when  separated  from  the  globules.  It  is 
evident,  therefore,  tliat  the  globules  liave  the 
power  of  combining  with  gases. 

The  globules  of  the  blood  change  their 
colour  in  different  gases;  and  this  change 
may  be  owing  either  to  a  combination  or  to 
a  decomposition. 

Sulphuretted  hvdrogen  turns  them  black- 
ish green  and  finally  black ;  and  the  original 
red  colour  cannot,  in  this  case,  be  restored 
by  contact  with  oxygen.  Here  a  decompo- 
sition has  obviously  taken  place. 

The  globules  darkened  by  carbonic  acid 
become  again  florid  in  oxygen,  with  disen- 
gagement of  carbonic  acid.  The  same  thing 
takes  place  in  nitrous  oxide.  It  is  clear  that 
they  have  here  undergone  no  decomposition, 
and,  consequently,  they  possess  the  power 
of  combining  with  gases,  while  the  compound 
they  form  with  carbonic  acid  is  destroyed  by 
oxygen.  When  left  to  themselves,  out  01 
the  body,  the  compound  formed  with  oxy- 
gen again  becomes  dark,  but  does  not 
recover  its  florid  colour  a  second  time  by 
the  action  of  oxygen. 

The  globules  of  the  blood  contain  a  com- 
pound of  iron.  From  the  never-failing 
presence  of  iron  in  red  blood,  we  must  con- 
clude, that  it  is  unquestionably  necessary 
to  animal  life;  and,  since  physiology  has 
proved,  that  the  globules  take  no  share  in 
the  process  of  nutrition,  it  cannot  be  doubted 
that  they  play  a  part  in  the  process  of  re- 
spiration. 

The  compound  of  iron  in  the  globules 
has  the  characters  of  an  oxidized  com- 
pound ;  for  it  is  decomposed  by  sulphuretted 
hydrogen,  exactly  in  the  same  way  as  the 
oxides  or  other  analogous  compounds  of 
iron.  By  means  of  diluted  mineral  acids, 
peroxide  'sesquioxide)  of  iron  may  be  ex- 
tracted, at  the  ordinary  temperature,  from 
the  fresh  or  dried  red  colouring  matter  of 
the  blood. 

The  characters  of  the  compounds  of  iron 
may,  perhaps,  assist  us  to  explain  the  share 
which  that  metal  takes  in  the  respiratory 
process.  No  other  metal  can  be  compared 
with  iron,  for  the  remarkable  properties  of 
its  compounds. 


The  compounds  of  protoxide  of  iron  pos- 
sess the  property  of  depriving  other  oxidized 
compounds  of  oxygen;  while  the  compounds 
of  peroxide  of  iron,  under  other  circum- 
stances, give  up  oxygen  with  the  utmost 
facility. 

Hydra  ted  peroxide  of  iron,  in  contact 
with  organic  matters  destitute  of  sulphur, 
is  converted  into  carbonate  of  the  protoxide. 

Carbonate  of  protoxide  of  iron,  in  con- 
tact with  water  and  oxygen,  is  decomposed ; 
all  the  carbonic  acid  is  given  off,  and,  by 
absorption  of  oxygen,  it  passes  into  the 
hydrated  peroxide,  which  may  again  be  con- 
verted into  a  compound  of  the  protoxide. 

Not  only  the  oxides  of  iron,  but  also  the 
cyanides  of  that  metal,  exhibit  similar  pro* 
perties.  Prussian  blue  contains  iron  ip 
combination  with  all  the  organic  elements 
of  the  body ;  hydrogen  and  oxygen  (water) 
carbon  and  nitrogen  (cyanogen.) 

When  it  is  exposed  to  light,  cyanogen  is 
given  off,  and  it  becomes  white ;  in  the  dark 
it  extracts  oxygen,  and  recovers  its  blue 
colour. 

All  these  observations,  taken  together, 
lead  to  the  opinion  that  the  globules  of  arte- 
rial blood  contain  a  compound  of  iron  satu- 
rated with  oxygen,  which,  in  the  living 
blood,  loses  its  oxygen  during  its  passage 
through  the  capillaries.  The  same  thing 
occurs  when  it  is  separated  from  the  body, 
and  begins  to  undergo  decomposition  (to  pu- 
trefy.) The  compound,  rich  in  oxygen, 
passes,  therefore,  by  the  loss  of  oxygen  ("re- 
duction) into  one  far  less  charged  with  tha: 
element.  One  of  the  products  of  oxidation 
formed  in  this  process  is  carbonic  acid.  The 
compound  of  iron  in  the  venous  blood  pos- 
sesses the  property  of  combining  with  car- 
bonic acid ;  and  it  is  obvious,  that  the  glo- 
bules of  the  arterial  blood,  after  losing  a  part 
of  their  oxygen,  will,  if  they  meet  with  car- 
bonic acid,  combine  with  that  substance. 

When  they  reach  the  lungs,  they  wil' 
again  take  up  the  oxygen  they  have  lost ; 
for  every  volume  of  oxygen  absorbed,  a  cor- 
responding volume  of  carbonic  acid  will  be 
separated ;  they  will  return  to  their  former 
state ;  that  is,  they  will  again  acquire  the 
power  of  giving  off  oxygen. 

For  every  volume  of  oxygen  which  the 
globules  can  give  off,  there  will  be  formed 
(as  carbonic  acid  contains  its  own  volume 
of  oxygen,  without  condensation)  neither 
more  nor  less  than  an  equal  volume  of  car- 
bonic acid.  For  every  volume  of  oxygen 
which  the  globules  are  capable  of  absorbing, 
no  more  carbonic  acid  can  possibly  be  sepa- 
rated than  the  volume  of  oxygen  can  pro- 
duce. 

When  carbonate  of  protoxide  of  iron,  by 
the  absorption  of  oxygen,  passes  into  the 
hydrated  peroxide,  there  are  given  off,  for 
every  volume  of  oxygen  necessary  to  the 
change  from  protoxide  to  peroxide,  four  vo- 
lumes of  carbonic  acid  gas. 

But  from  one  volume  of  oxygen  only  on? 
volume  of  cabronic  acid  can  be  produced, 


THEORY  OF   RESPIRATION. 


79 


And  the  absorption  of  one  volume  of  oxygen 
can  only  cause,  directly,  the  separation  of 
an  equal  body  of  caroonic  acid.  Conse- 
quently, the  substance  or  compound  which 
has  lost  its  oxygen,  during  the  passage  of 
arterial  into  venous  blood,  must  have  been 
capable  of  absorbing  or  combining  with  car- 
bonic acid  ;  and  we  find,  in  point  of  fact, 
that  tne  living  blood  is  never,  in  any  state, 
saturated  with  carbonic  acid ;  that  it  is  capa- 
ble of  taking  up  an  additional  quantity, 
without  any  apparent  disturbance  of  the 
function  of  the  globules.  Thus,  for  exam- 
ple, after  drinking  effervescing  wines,  beer, 
or  mineral  waters,  more  carbonic  acid 
must  necessarily  be  expired  than  at  other 
times.  In  all  cases,  where  the  oxygen  of 
the  arterial  globules  has  been  partly  ex- 
pended, otherwise  than  in  the  formation  of 
carbonic  acid,  the  amount  of  this  latter  gas 
expired  will  correspond  exactly  with  that 
which  has  been  formed ;  less,  however,  will 
be  given  out  after  the  use  of  fat  and  of  still 
wines,  than  after  champagne. 

According  to  the  views  now  developed, 
the  giobules  of  arterial  blood,  in  their  pas- 
sage through  the  capillaries,  yield  oxygen 
to  certain  constituents  of  the  body.  A  small 
portion  of  this  oxygen  serves  to  produce  the 
change  of  matter,  and  determines  the  sepa- 
ration 01  living  parts  and  their  conversion 
into  lifeless  compounds,  as  well  as  the  form- 
ation of  tne  secretions  and  excretions.  The 
greater  part,  however,  of  the  oxygen  is  em- 
ployed in  converting  into  oxidized  com- 
pounds the  newly  formed  substances,  which 
no  longer  form  part  of  the  living  tissues. 

In  their  roturn  towards  the  heart,  the 
globules  which  have  lost  their  oxygen  com- 
bine with  carbonic  acid,  producing  venous 
blood ;  and,  when  they  reach  the  lungs,  an 
exchange  takes  place  between  this  carbonic 
acid  and  the  oxygen  of  the  atmosphere. 

The  organic  compound  of  iron,  which 
exists  in  venous  blood,  recovers  in  the  lungs 
the  oxygen  it  has  lost,  and,  in  consequence 
of  this  absorption  of  oxygen,  the  carbonic 
acid  in  combination  with  it  is  separated. 

All  the  compounds  present  in  venous 
blood,  which  have  any  attraction  for  oxygen, 
are  converted,  in  the  lungs,  like  the  glo- 
bules, into  more  highly  oxidized  com- 
pounds ;  a  certain  amount  of  carbonic  acid 
is  formed,  of  which  a  part  always  remains 
di?°olved  in  the  serum  of  the  blood. 

The  quantity  of  carbonic  acid  dissolved, 
or,  of  that  combined  with  soda,  must  be 
equal  in  venous  and  arterial  blood,  since 
both  have  the  same  temperature  ;  but  arterial 
blood,  when  drawn,  must,  after  a  short  time, 
contain  a  larger  quantity  of  carbonic  acid 
than  venous  blood,  because  the  oxygen  of 
the  globules  is  expended  in  producing  that 
compound. 

Hence,  in  the  animal  organism,  two  pro- 
cesses of  oxidation  are  going  on ;  one  in 
the  lungs,  the  other  in  the  capillaries.  By 
means  of  the  former,  in  spite  cf  the  degree 
of  cooling,  and  of  the  increased  evapora- 


tion which  takes  place  there,  the  constan 
temperature  of  the  lungs  is  kept  up;  while 
the  neat  of  the  rest  of  the  body  is  supplied 
by  the  latter. 

A  man,  who  expires  daily  13-9  oz.  of  car- 
bon, in  the  form  of  carbonic  acid,  consumes, 
in  24  hours,  37  oz.  of  oxygen,  which  occupy 
a  space  equal  to  807  litres=51,648  cuoic 
inches  (Hessian.) 

If  we  reckon  18  respirations  to  a  minute, 
we  have,  in  24  hours,  25,920  respirations  ; 
and,  consequently,  in  each  respiration,  there 
are  taken  into  the  blood  fi||§=l'99  cubic 
inch  of  oxygen. 

In  one  minute,  therefore,  there  are  added 
to  the  constituents  of  the  blood  18  X  1'99= 
35-8  cubic  inches  of  oxygen,  which,  at  the 
ordinary  temperature,  weigh  rather  less  than 
12  grains. 

If  we  now  assume,  that  in  one  minute  10 
Ibs.  of  blood  pass  through  the  lungs,  (Miiller, 
Physiologie,  vol.  i.  p.  345,)  and  that  this 
quantity  of  blood  measures  320  cubic  inches, 
then  1  cubic  inch  of  oxygen  unites  with  9 
cubic  inches  of  blood,  very  nearly. 

According  to  the  researches  of  Denis, 
Richardson,  and  Nasse  (Handworterbuch 
der  Physiologie,  vol.  i.  p.  138,)  10,000  parts 
of  blood  contain  8  parts  of  peroxide  of  iron. 
Consequently,  76,800  grains  (10  Ibs.  Hes- 
sian) of  blood  contain  61-54  grains  of  per- 
oxide of  iron  in  arterial  blood,  =  55' 14  of 
protoxide  in  venous  blood. 

Let  us  now  assume  that  the  iron  of  the 
globules  of  venous  blood  is  in  the  state  of 
protoxide.  It  follows,  that  55*14  grains  of 
protoxide  of  iron,  in  passing  through  the 
lungs,  take  up,  in  one  minute,  6*40  grains 
of  oxygen  (the  quantity  necessary  to  con- 
vert it  into  peroxide.)  But  since,  in  the 
same  time,  the  10  Ibs.  of  blood  have  taken 
up  12  grains  of  oxygen,  there  remain  5-60 
grains  of  oxygen,  which  combine  with  the 
other  constituents  of  the  blood. 

Now,  55-14  grains  of  protoxide  of  iron 
combine  with  34-8  grains  of  carbonic  acid, 
which  occupy  the  volume  of  73  cubic  inches. 
It  is  obvious,  therefore,  that  the  amount  of 
iron  present  in  the  blood,  if  in  the  state  of 
protoxide,  is  sufficient  to  furnish  the  means 
of  carrying  or  transporting  twice  as  much 
carbonic  acid  as  can  possibly  be  formed  by 
the  oxygen  absorbed  in  the  lungs. 

The  hypothesis  just  developed  rests  on 
well-known  observations,  and,  indeed,  ex- 
plains completely  the  process  of  respiration, 
as  far  as  it  depends  on  the  globules  of  the 
blood.  It  does  not  exclude  the  opinion  that 
carbonic  acid  may  reach  the  lungs  in  other 
ways ;  that  certain  other  constituents  of  the 
blood  may  give  rise  to  the  formation  of  car- 
bonic acid  in  the  lungs.  But  all  this  has  no 
connexion  with  that  vital  process  by  which 
the  heat  necessary  for  the  support  of  life  is 
generated  in  every  part  of  the  body.  Now 
it  is  this  alone  which,  for  the  present,  can 
be  considered  as  the  object  truly  worthy  of 
investigation.  It  is  not,  indeed,  uninterest 
ing  to  inquire,  why  dark  blood  becomes 


ANIMAL  CHEMISTRY. 


florid  by  the  action  of  nitre,  common  salt, 
k,c.;  but  this  question  has  no  relation  to 
the  natural  respiratory  process. 

The  frightful  effects  of  sulphuretted  hy- 
drogen, and  of  prussic  acid,  which,  when 
inspired,  put  a  stop  to  all  the  phenomena 
of  motion  in  a  few  seconds,  are  explained 
in  a  natural  manner  by  the  well-known 
action  of  these  compounds  on  those  of  iron, 
when  alkalies  are  present;  and  free  alkali 
is  never  absent  in  the  blood. 

Let  us  suppose  that  the  globules  Jose  their 
property  of  absorbing  oxygen,  and  of  after- 
wards giving  up  this  oxygen  and  carrying 
off  the  resulting  carbonic  acid;  such  a  hy- 
pothetical state  of  disease  must  instantly 
become  perceptible  in  the  temperature  and 
other  vital  phenomena  of  the  body.  The 
change  of  matter  will  be  arrested,  while 
yet  the  vital  motions  will  not  be  instantly 
stopped. 

The  conductors1  of  force,  the  nerves,  will 
convey,  as  before,  to  the  heart  and  intestines 
the  power  necessary  for  their  functions. 
This  power  they  will  receive  from  the  mus- 
cular system,  while,  as  no  change  of  matter 
takes  place  in  the  latter,  the  supply  must 
soon  fail.  As  no  change  of  matter  occurs, 


no  lifeless  compounds  are  separated,  neitnei 
bile  nor  urine  can  be  formed ;  and  the  tent 
perature  of  the  body  must  sink. 

This  state  of  matters  soon  puts  a  stop  lo 
the  process  of  nutrition,  and  sooner  or  later 
death  must  follow,  but  unaccompanied  by- 
febrile  symptoms,  which  in  this  case  is  a 
very  important  fact. 

This  example  has  been  selected  in  order 
to  show  the  importance  and  probable  advan- 
tage of  an  examination  of  the  blood  in  analo- 
gous diseased  conditions.  It  cannot  be,  in 
the  slightest  degree,  doubtful  that  the  func- 
tion ascribed  to  the  blood  globules  may  be 
considered  as  fully  explained  and  cleared 
up,  if,  in  such  morbid  conditions,  we  shall 
discover  a  change  in  their  form,  structure, 
or  chemical  characters,  a  change  which 
must  be  recognizable  by  the  use  of  appro- 
priate re-agents. 

If  we  consider  the  force  which  determines 
the  vital  phenomena  as  a  property  of  cer- 
tain substances,  this  view  leads  of  itself  to 
a  new  and  more  rigorous  consideration  of 
certain  singular  phenomena,  which  these 
very  substances  exhibit,  in  circumstances  in 
which  they  no  longer  make  a  part  of  living 
organisms. 


APPENDIX: 


CONTAINING  THE  ANALYTICAL  EVIDENCE  REFERRED  TO  IN  THE  SEC- 
TIONS  IN  WHICH  ARE  DESCRIBED  THE  CHEMICAL  PROCESSES  OF  RE- 
SPIRATION,  OF  NUTRITION,  AND  OF  THE  METAMORPHOSIS  OF  TISSUES. 

%*  The  Notes  correspond  with  the  numbers  in  parentheses  in  the  text.  All  the  Analyses  quoted, 
which  have  the  mark  *  attached,  have  been  made  in  the  chemical  laboratory  of  the  University  of 
Giessen. 


INTRODUCTION    TO    THE    ANALYSES. 


THE  method  formerly  employed  to  exhibit  the  differences  in  composition  of  different 
substances,  that,  namely,  of  giving  the  proportions  of  the  various  elements  in  100  parts, 
has  been  long  abandoned  by  chemists ;  because  it  affords  no  insight  into  the  relations 
which  exist  between  two  or  more  compounds.  In  order  to  give  some  proofs  of  this  state- 
ment, we  shall  here  state,  in  that  form,  the  composition  of  aldehyde  and  acetic  acid,  of 
oil  of  bitter  almonds  and  benzoic  acid. 


Acetic  acid.  Aldehyde.  Benzoic  acid. 

Carbon        40-00  55-024  69-25 

Hydrogen     6-67  8-983  4-86 

Oxygen       53-33  35-993  25.89 


Oil  of  bitter  almonds. 

79-56 
5-56 

14-88 


Now  aldehyde  is  converted  into  acetic  acid,  and  oil  of  bitter  almonds  into  benzoic  acid, 
simply  by  the  addition  of  oxygen,  without  any  change  in  regard  to  the  other  elements. 
This  important  relation  cannot  be  traced  in  the  mere  numerical  results  of  analysis  as 
above  given ;  but  if  the  composition  of  the  related  compounds  be  expressed  in  formulae, 
according  to  equivalents,  the  connexion  in  each  case  becomes  obvious,  even  to  him  who 
Knows  no  more  of  chemistry  than  that  C  represents  an  equivalent  or  combining  portion 
of  carbon,  H  an  equivalent  of  hydrogen,  and  O  an  equivalent  of  oxygen. 


Formula 

J^ 


Formula 


of  acetic  acid. 


of  aldehyde. 

C4H402. 


of  benzoic  acid. 

C14H6O4. 


of  oil  of  bitter  almondi. 

C14H6O2. 


APPENDIX.— ANALYTICAL  EVIDENCE.  *' 

These  formulae  are  exact  expressions  of  the  results  of  analysis,  which,  in  each  of  the 
two  cases  quoted,  refer  to  a  fixed  quantity  of  carbon ;  in  one  to  4  equivalents,  in  the 
other  to  14.  They  show,  that  acetic  acid  differs  from  aldehyde,  and  benzoic  acid  from 
oil  of  bitter  almonds,  only  in  the  proportion  of  oxygen. 

Nor  is  it  more  difficult  to  understand  the  signification  of  the  following  formulae. 

Cyamelide.  1  eq.  cyanurie  acid.  3  eq.  hydrated  cyanic  acid. 

C6N3H3O6=Cy3(=06N3)03+3HO=3(CyO+HO)= 
=CflN3H3O6  =C«N3H3O6. 

(In  these  formulae,  N  represents  an  equivalent  of  nitrogen,  and  Cy  an  equivalent  of 
cyanogen.  This  latter  substance  being  composed  of  2  equivalents  of  carbon  and  1  eq.  of 
nitrogen,  Cy  =  C2N.) 

The  first  formula  (that  of  Cyamelide)  is  what  is  called  an  empirical  formula,  in  which 
the  relative  proportions  of  the  elements  are,  indeed,  exactly  known,  but  where  we  have 
not  even  a  theory,  far  less  any  actual  knowledge,  of  the  order  in  which  they  are  arranged. 
The  second  formula  is  intended  to  express  the  opinion  that  3  eq.  of  cyanogen  (=  6  eq.  of 
carbon  +  3  eq.  of  nitrogen)  having  united  to  form  a  compound  atom  or  molecule,  have 
combined  with  3  eq.  of  oxygen  and  3  eq.  of  water,  to  form  1  eq.  of  hydrated  cyanurie 
acid.  The  third  expresses  the  order  in  which  the  elements  are  supposed  to  be  arranged 
in  hydrated  cyanic  acid,  the  whole  multiplied  by  3.  Each  equivalent  of  cyanic  acid  is 
formed  of  1  eq.  of  cyanogen,  1  eq.  of  oxygen,  and  1  eq.  of  water;  and  hence  the  same 
number  of  atoms  of  each  element,  which  together  formed  1  eq.  of  cyanuric  acid,  is  here 
so  divided  as  to  yield  3  eq.  of  cyanic  acid. 

We  have  here,  therefore,  the  same  absolute  and  relatrre  amount  of  atoms  of  each  ele- 
ment, arranged  in  three  different  ways ;  yet  in  each  of  these  the  proportions  of  the  ele- 
ments, calculated  for  100  parts,  must  of  course  be  the  same.  It  is  easy,  therefore,  to  see 
the  advantage  we  possess  by  the  use  of  formulae  ;  that,  namely,  of  exhibiting  the  relations 
existing  between  compounds  of  different  composition ;  and  that  also  of  expressing  the 
actual,  probable,  or  possible  differences  between  substances  whose  composition,  in  100 
parts,  is  the  same,  while  their  properties,  as  in  the  case  above  quoted,  are  perfectly 
distinct. 

It  does  not  come  within  our  province  here  to  explain  the  method  or  rule  by  which 
the  composition  of  a  substance,  in  100  parts,  (as  it  is  always  obtained  in  analysis,)  is  ex- 
pressed in  a  formula ;  we  shall  only  describe  the  rule  for  calculating,  from  a  given 
formula,  the  composition  in  100  parts.  For  this  purpose  it  must  be  noted  that  C,  in  a 
chemical  formula,  signifies  a  weight  of  carbon  expressed  by  the  number  76*437  (accord- 
ing to  the  most  recent  determinations  75-8  or  75-0,  a  variation  which  has  no  effect  what- 
ever on  the  formulae  here  adduced,  all  of  which  are  calculated  on  the  number  76437) , 
that  H  signifies  a  weight  of  hydrogen  —  12-478;  N  a  weight  of  nitrogen  =1 77-04  j  and 
lastly,  O  a  weight  of  oxygen  =  100. . 

The  formula  of  proteine,  C^N6!!3^14,  expresses,  therefore, 

48  times  76-437  —  3668-88  carbon, 
6  times  177-040  —  1062-24  nitrogen, 
36  times    12-478  —    449-26  hydrogen, 
14  times  100-000=  1400-00  oxygen. 

The  sum  gives  a  weight  of  6580*38  proteine. 

Therefore— 

In  100  pans. 

In  6580-38  parts  of  proteine  are  contained                          3668-88  carbon  55-742 

In  6580-38                     ditto                                                 1062-24  nitrogen  16-143 

In  6580-38                     ditto                                                   449-26  hydrogen  6-827 

In  6580-38                    ditto                                                1400-00  oxygen  21-288 

100-000 

The  actual  results  of  analysis,  reduced  to  100  parts,  when  compared  with  the  abcve 
numbers,  will  show  how  far  the  assumed  formula  is  corect  j  or,  supposing  the  formula 
ascertained,  they  will  show  the  degree  of  accuracy  displayed  by  the  experimenter. 
Thus  the  proportions  in  100  parts,  calculated  from  the  formula,  furnish  an  important 
check  to  the  opentor,  and,  conversely,  the  formula  calculated  from  his  results,  when 
compared  with  other  known  formulas,  supplies  a  test  of  his  accuracy,  or  of  the  purity  of 
the  substance  analyzed. 

11 


ANIMAL   CHEMISTRY. 


NOTE  (1,)  p.  14. 

CONSUMPTION    OF    OXYGEN   BY   AN   ADULT. 

Jin  adult  man. 

, « »  Carbon  contained. 


According  to 

cubic  in.    grains. 

Lavoisier  and  Seguin  46,037  15,661 
Menzies      ....  51,480  17,625 

Davy 45,504  15,751 

Allen  and  Pepys  .    .  39,600  13,464 


consumes  of  oxygen  produces  of  carbonic  in  the 

in  24  hours.  acid  in  24  hours.        carbonic  acid. 


cubic  in. 

14,930 


§pams. 
,584 


31,680  17,811 
39,600  18,612 


4,853 
5,148 


French. 
English 

do. 

do. 


NOTE   (2,)  p.  14. 

COMPOSITION   OF   DRY    BLOOD    (see  Note  28.) 

In  100  parts.        In  4-8  Ibs.  Hessiam  =  36,864  grains. 

Carbon.        .  .    51-96  .        .        .     19154-5 

Hydrogen.  .          7-25  .        .        .          26727 

Nitrogen        .  .     15-07  .        .        .       5555-4 

Oxygen     .  .        21-30  .        .       »"        7852-0 

Ashes            .  .      4-42  .        .        .       1629-4 

100-00  36864-0 

Grains.  Grains. 

19154-5  carbon  form,  with  50539-5  oxygen,  carbonic  acid. 
2672'7  hydrogen    do.       21415-8     do.      water. 


Sura  =  71955-3 

Deduct  oxygen  present  £  __  7852-0 
in  blood    .        .        .  J 


do. 


Remain     64103-3  grains  of  oxygen,  required  for  the 
complete  combustion  of  4-8  Ibs.  of  dry  blood. 

It  is  assumed  in  this  calculation,  that  24  Ibs.  of  blood  yield  4-8  Ibs.  (20  per  cent.)  of 
dry  residue.    The  remainder,  80  per  cent.,  is  water. 

NOTE  (3,)  p.  14. 
DETERMINATION  OF  THE  AMOUNT  OF  CARBON  EXPIRED. 

1.  ANALYSIS  OF 

Fo&ces. 

2-356  dry  faeces  left  0-320  ashes  (13-58  per  cent.) 
0-352  dry  faeces  yielded  0-576  carbonic  acid,  and  0-218  water. 

Lentils. 
0-566  lentils,  dried  at  212°,  yielded  0-910  carbonic  acid,  and  0-366  water. 

Pease. 

1-060  pease,  dried  at  212°,  left  0-037  ashes. 
0-416    do.  do.  yielded  0-642  carbonic  acid,  and  0-241  water. 

Potatoes. 
0-443  dried  potatoes  yielded  0-704  carbonic  acid,  and  0-248  water. 

Black  Bread  (Schwarzbrod.} 

0-302  dried  black  bread  yielded  0-496  carbonic  acid,  and  0-175  water. 
0-241  do.  0-393  do.  0-142    do. 

From  the  above,  which  are  the  direct  results  of  experiment,  the  composition  in  100 
parts  is  calculated  as  in  the  following  table. 

2.  COMPOSITION 

Of  Faeces.  Of  Black  Bread.     Of  Potatoes.     Of  Flesh. 


Playfair.* 

Bceckmann.* 

Boussingault.    Bceckmann.* 

Carbon 

45-24 

45-09 

45-41 

44-1 

43-944 

(See  note  28) 

Hydrogen 

6-88 

6-54 

6-45 

5-8 

6-222 

Nitrogen  > 
Oxygen  J 

34-73 

45-12 

44-89 

45-1 

44-919 

AT 

Ashes 

13-15 

3-25 

3-25 

5-0 

4-915 

Water 


100-00    100-00    100-00    100-0    100-000 
300-00 


400-00 


APPENDIX.— ANALYTICAL  EVIDENCE. 


83 


Carbon 
Hydrogen 
Nitrogen    > 
Oxygen    $" 
Asnes    . 
Water 


Water 
Dry  Matter 


75    74-8 
25    25-2 

100  100-0 


Of  Pease. 
Playfair.* 

35-743 
5-401 

Of  Lentils.       Of  Beans. 
Playfair.*               Plavfair.* 

37-38           38*24 
5-54             5-84 

39-366 

37-98           38-  r 

3-490 
16-000 

3-20             3-71 
15-90            14-11 

100-000 

100-00          100-OC 

Potatoes. 
Boussingault.* 

72-2 

27-8 

BiacK  Bread. 
Boeckmann.* 

A 

73-2        33        31-418 
26-8       67       68-592 

100-0        100-0      100      100-000 


3.  CALCULATION, 

with  the  help  of  the  preceding  data,  of  the  amount  of  carbon  expired  by  an  adult  man. 
The  following  results  are  deduced  from  observations  made  (see  table)  on  the  average 
daily  consumption  of  food,  by  from  27  to  30  soldiers  in  barracks  for  a  month,  or  by  855 
men  for  one  day.  The  food,  consisting  of  bread,  potatoes,  meat,  lentils,  pease,  beans,  &,c., 
was  weighed,  with  the  utmost  exactness,  every  day  during  a  month  (including  even  pep- 
per, salt,  and  butter ;)  and  each  article  of  food  was  separately  subjected  to  ultimate  analysis. 
The  only  exceptions,  among  the  men,  to  the  uniform  allowance  of  food,  were  three  soldiers 
of  the  guard,  who,  in  addition  to  the  daily  allowance  of  2  Ibs.  of  bread,  received,  during 
each  of  the  periods  allotted  for  the  pay  of  the  troops,  2$  Ibs.  extra;  and  one  drummer  who, 
in  the  same  period,  left  2£  Ibs.  unconsumed.  According  to  an  approximative  report  by 
the  sergeant-major,  each  soldier  consumes  daily,  on  an  average,  out  of  barracks,  3  oz. 
of  sausage,  £  oz.  of  butter,  £  pint  of  beer,  and  y^  pint  of  brandy ;  the  carbon  of  which 
articles  amounts  to  more  than  double  that  of  the  faeces  and  urine  taken  together.  In  the 
soldier,  the  faces  amount  daily,  on  an  average,  to  5£  oz.;  they  contain  75  per  cent,  of 
water,  and  the  dry  residue  contains  45-24  per  cent,  of  carbon,  and  13-15  per  cent,  of 
ashes.  100  parts  of  fresh  faeces  consequently  contain  11-31  per  cent,  of  carbon,  very 
nearly  the  same  proportion  as  in  fresh  meat.  In  the  calculation,  the  carbon  of  the  faeces 
and  of  the  urine  has  been  assumed  as  equal  to  that  of  green  vegetables,  and  of  the  food 
(sausages,  butter,  beer,  &c.)  consumed  in  the  alehouse. 

From  the  observations,  as  recorded  in  the  table,  the  following  conclusions  are  deduced. 

Flesh. — Meat  devoid  of  fat,  if  reckoned  at  74  per  cent,  water,  and  26  per  cent,  dry  matter, 

contains  in  100  parts  very  nearly  13-6  parts  of  carbon.   Ordinary  meat  contains  both  fat  and 

cellular  tissue,  which  together  amount  to  ^th  of  the  weight  of  the  meat  as  bought  from  the 

butcher.  The  number  of  ounces  consumed  (by  855  men)  was  4,448,  consisting,  therefore,  of 

3812-5  oz.  of  flesh,  free  from  fat,  containing  of  carbon  518-5  oz. 

635-5  oz.  of  fat  and  cellular  tissue,  ditto  449-0  oz. 


4448-0  oz.  In  all,  carbon  967-5  oz. 

With  the  bones,  the  meat,  as  purchased,  contains  29  per  cent,  of  fixed  matter,  including 
bones  ;  4,448  oz.  of  flesh  therefore  contain  448  oz.  of  dry  bones.  These  have  not  been 
included  in  the  calculation,  although,  whe-n  boiled,  they  yield  from  8  to  10  per  cent,  of 
gelatine,  which  is  taken  as  food  in  the  soup. 

Fat. — The  amount  of  fat  consumed  was  56  oz.;  which,  the  carbon  being  calculated 
at  80  per  cent.,  contain  in  all  44*8  oz.  of  carbon. 

Lentils,  pease  and  beans. — There  were  consumed  53*5  oz.  of  lentils,  185-5  oz.  of  pease 
and  218  oz.  of  beans.  Assuming  the  average  amount  of  carbon  in  these  vegetables  to 
be  37  per  cent.,  the  total  quantity  of  carbon  consumed  in  this  form  was  169-1  oz. 

Potatoes. — 100  parts  of  fresh  potatoes  contain  12*2  parts  of  carbon.  In  the  15*876  oz. 
of  potatoes  consumed,  therefore,  the  amount  of  carbon  was  1936*85  oz. 

Bread. — 855  men  eat  daily  855  times  32  oz.,  besides  36  Ibs.  of  bread  in  the  soup, 
which  in  all  amounts  to  27,936  oz.     100  oz.  of  fresh  bread  contain,  on  an  average,  30*15 
oz.  of  carbon  ;  consequently  the  carbon  consumed  in  ihe  bread  amounts  to  8771-5  oz. 
The  total  consumption,  therefore,  was, 

In  the  meat 967-50  oz.  of  carbon 

In  the  fat 44-80  ditto 

In  the  lentils,  pease,  and  beans  .        •  169*10  ditto 

In  the  potatoes 1936-85  ditto 

In  the  bread  .  .          8771-50  ditto 


Consumed  by  855  men 
Consumed  by  1  man 


ditto 
ditto 


84 


ANIMAL  CHEMISTRY. 


Ill  II 

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APPENDIX.— ANALYTICAL  EVIDENCE.  85 

The  faeces  of  a  soldier  weigh  5*5  oz.,  and  contain,  in  the  fresh  state,  11  per  cent,  of 
carbon.  For  86  kreutzer  (about  2s.  5d.  sterling,)  there  may  be  bought,  on  an  average, 
172  Ibs.  of  vegetables,  sucn  as  cabbages,  greens,  turnips,  &c.;  25  maas  of  sour  krout 
weigh  100  Ibs.  j  and  for  48^  kreutzer  (Is.  5d.  sterling,)  there  are  brought,  on  an  average, 
24£  Ibs.  of  onions,  leeks,  celery,  &c.*  855  men  consumed 

Of  green  vegetables 2,802  oz. 

Of  sour  krout 1,600 

Of  onions,  &c.       .        .        .  -  -  **•-"    ,|  - .        .  388 

.en  all        .       .    :   ^  •'*;•'    .        .    4,790 

And  one  man         *  ^   j*,/     *r  <;   '4       »4   ^ .        .  5-6  oz. 

For  this  reason,  the  carbon  of  the  last  mentioned  articles  of  food  has  been  assumed  as 
equal  to  that  of  the  fasces  and  urine.  Sausages,  brandy,  beer,  in  short,  the  small  quantity 
of  food  taken  irregularly  in  the  alehouse,  has  not  been  included  in  the  calculation. 

The  daily  allowance  of  bread,  being  uniformly  2  Ibs.  per  man,  with  the  exceptions 
formerly  mentioned,  has  not  been  inserted  in  "the  table,  which  includes  only  those 
matters  of  which,  from  the  daily  allowance  being  variable,  an  average  was  required. 
The  small  quantity  of  bread  in  the  table  is  that  given  in  the  soup,  which  is  over  and 
above  the  daily  supply. 

NOTE  (4.)    See  next  page. 
NOTE  (5,)  p.  15. 

TEMPERATURE    OP   THE   BLOOD   AND   FREQUENCY   OP   THE    PTJLSE. 


According  to  Prevost  and  Dumas. 

The  frequency 

tc 

In  the  Pigeon 
Common  Fowl 
Duck       ... 

Raven      .        .  L     • 
Lark            .        .;     . 
Simia  Callitriche 
Guinea  Pig 
Dog          .      >v-W 
Cat      .... 

:mperature  rs                 of  the  pulse 
F.                          in  the  minute. 

107-6°      .        .    136      . 
106-7    .        .        140  . 
108-5        .        .    170      . 
108-5    .        .        110  . 
117-2        .        .    200      . 
95-9    .        .         90  . 
100-4        .        .    140      . 
99-3    .        .         90  . 
101-3        .        .    100      . 
102-5    .                  84  . 
100-4        .        .    120      . 
98-2    .                  56  . 
98-6     ;  «             72 

of  the  respiration 
in  the  minute. 

.    34 
30 
.    21 
Y      21 
.    22 
30 
.    36 
28 
.    24 
.        24 
.    36 
...       16 
.    18 

Goat 
Hare    .... 
Horse 
Man     .... 

Man  (Liebig)  . 
Woman  (Liebig)       '  * 

97-7° 
98-2    . 

65      . 
60  . 

.    17 
15 

The  temperature  of  a  child  is  102-2°. 

The  temperature  of  the  human  body,  in  the  mouth  or  in  the  rectum,  for  example,  is 
from  97-7°  to  98-6°.  That  of  the  blood  (Majendie)  is  from  100-6°  to  101-6°.  As  a  mean 
temperature,  99-5°  has  been  adopted  in  this  work,  page  15. 

NOTE  (6,)  p.  20. 

The  prisoners  in  the  house  of  arrest  of  Giessen  receive  daily  1$  lb.  of  bread  (24  oz.,') 
which  contain  7i  oz.  of  carbon.  They  receive,  besides,  1  Ib.  of  soup  daily,  and  on  each 
alternate  day,  1  Ib.  of  potatoes. 

1£  Ib.  of  bread  contains        ....         7'25  oz.  of  carbon. 

1     Ib.  of  soup  contains 0-75  ditto. 

i  Ib.  of  potatoes  contains    .        .        .        .         1-00  ditto. 

Total 9-00  ditto.f 

*  In  the  original  table,  the  quantities  of  these  vegetables  are  entered  according  to  their  value  in 
Kreutzers,  but  they  are  here  calculated  by  weight  from  the  above  data,  as  this  appeared  better 
adapted  for  comparison  in  this  country  than  the  prices  would  have  been. — ED. 

t  At  page  36  the  carbon  contained  in  the  dailyfood  of  these  prisoners  is  calculated  at  8£  oz.,  and 


ANIMAL   CHEMISTRY. 


>-*  d 

O  S) 


SS   I 

00  CM 


, 

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CM  CO 


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S  **  S 


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APPENDIX.— ANALYTICAL   EVIDENCE. 


NOTE  (7,)  p.  21. 

COMPOSITION    OP    THE    FIBRINE    AND    ALBUMEN    OF    BLOOD.  <J. 

Albumen  from  Serum  of  Blood.  Fibrine. 


Soberer.* 


Scherer. 


Mulder. 


53-850 
6-983 
15-673 


ii. 

55-461 
7-201 
15-673 


in. 

56-097 
6-880 
15-681 


53-671 

6-878 

15-763 


ii. 

54-454 
7-069 
15-762 


in. 

54-56 
6-90 
15-72 


23-494  21-655  22-342  23-688  22-715  22-82 


Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus 

a  Annalen  der  Chem.  und  Pharm.,  XXVIIL,  74,  and  XL.,  33,  36. 

For  additional  analyses  of  animal  fibrine  and  albumen,  see  Note  (27,)  wiiicn  also 
contains  analyses  of  the  various  animal  tissues. 

NOTE  (8,)  p.  22. 

COMPOSITION    OF    VEGETABLE    FIBRINE,    VEGETABLE     ALBUMEN,   VEGETABLE 
CASEINE,    AND    VEGETABLE    GLUTEN. 
VEGETABLE    FIBRINE. 

Sherer*o. 


GLUTEN, 

As  obtained  from  wheat  flour. 
Jones.*6      Marcet.c  Boussingault. 


I.  II.  III. 

53-064  54-603  54-617 

7-132  7-302  7-491 

15-359  15-809  15-809 


IV. 

53-83 
7-02 
15-58 


55-7 
14-5 

7-8 


ii. 

53-5 
150 

7-0 


Carbon 
Hydrogen 
Nitrogen 
Oxygen 
Sulphur 
Phosphorus  _ 
i  Ann.  der  Chem.  und  Pharm.,  XL.,  7.    6  Ibid.,  XL.,  65.    c  L.  Gmelin's  Theor.  Chemie,  II.,  1092. 


24-445    22-285    22-083      23-56      22-0      24-5 


VEGETABLE    ALBUMEN,  a. 


Carbon    . 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus 


From  Rye. 
Jones.* 

54-74 

7-77 

15-85 

21-64 


Wheat. 
Jones.* 

55-01 
7-23 


Gluten.  Almonds. 

Varrentrapp  &  Will.*  Jones.* 

54-85  57-03 

6-98  7-53 

15-88  13-48 


21-84 

Boussingault. 

,     527 
6-9 
18-4 
22-0 


22-39 


21-96 


Carbon      .        . 

Hydrogen 

Nitrogen    . 

Oxygen,  &c. . 

a  Ann.  der  Chem.  und  Pharm.,  XL,  66,  and  XXXIX.,  291. 


Varrentrapp  and  Will:* 

15-70 


VEGETABLE    CASEINE.a 


Scherer.* 


Jones.* 


Sulphate  of 
Caseine  and  Potash. 
Varrentrapp  and  Will. 


Carbon       .  '    .        .        54-138  55-05  51-41 

Hydrogen       .        .        .      7-156  7-59  7-83 

Nitrogen     .        .        •        15-672  15-89  14-48 

Oxygen,  &c.  .        .        .    23-034  21-47  

a  Ann.  der  Chem.  und  Pharm.,  XXXIX.,  291,  and  XL.,  8  and  67. 


51-24 
6-77 
13-23 


VEGETABLE  GLUTEN. 
Jones.  *a 


Boussingault. 


Carbon  .        .        .        55-22  54-2  52-3 

Hydrogen          .       .        .      7-42  7-5  6-5 

Nitrogen        .        .        .        15-98  13-9  18-9 

Oxygen,  &c.     .  21-38  24-4  22-3 

a  Ann.  der  Chem.  und  Pharm.,  XL.,  66. 

The  pure  gluten,  analyzed  by  Jones,  was  that  portion  of  the  raw  gluten  from  wheat 
flour  which  is  soluble  iii  hot  alcohol.  The  insoluble  portion  is  vegetable  fibrine,  the 
analysis  of  which  has  been  already  given. 

*lie  appendix  in  the  original  makes  the  number  also  8'5,  apparently  by  an  error  in  adding  up  the  above 
numbers,  which  yield  the  sum  of  9  oz.  Possibly  there  may  be  an  error  in  excess  in  the  proportion 
of  carbon  calculated  for  the  soup,  which,  in  that  case,  ought  to  le  0'25  oz.— EDITOR. 


ANIMAL   CHEMISTRY. 
NOTE  (9,)  p.  24. 

COMPOSITION   OF   ANIMAL    CASEINE.Cf 

Scherer. 


Carbon 
Hydrogen 

Nitrogen   , 


From  fresh              From  sour              From  milk  by 
milk.                        milk.                    acetic  acid. 

Albuminous  sub- 
stance in  mi  Ik.  6 

54-507 
6-913 
15-670 

54-825 
7-153 
15-628 

n. 
54-721 
7-239 
15-724 

in. 
54-665 
7-465 
15-724 

IV. 

54-580 
7-352 
15-696 

22-394 

22-316 

22-146 

22-372 

22-910 

a  Ann.  der  Chem.  und  Pharm.,  XL.,  40  et  seq. 

6  This  substance,  called,  in  German,  zieger,  is  contained  in  the  whey  of  milk  after  coagulation  by 
an  acid.    It  is  coagulated  by  heat,  and  very  much  resembles  albumen. 

Mulder.a 

';  v  ?v       .        .        .        54-96 


Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 


15-89 

21-73 

0-36 


a  For  the  analysis  of  vegetable  caseine,  see  the  preceding  note. 
NOTE  (10,)  p.  27. 

AMOUNT   OF   MATTER   SOLUBLE    IN   ALCOHOL    IN   THE    SOLID   EXCREMENTS   OF   THE 
HORSE    AND    COW.      (WILL.*) 

18-3  gramnes  of  dried  horse-dung  lost,  by  the  action  of  alcohol,  0-995  gramme.  The 
residue,  wnen  dry,  had  the  appearance  of  saw-dust,  after  it  had  been  deprived,  by  boiling, 
of  all  soluble  matter. 

14-98  grammes  of  dry  cow-dung  lost,  by  the  same  treatment,  0*625  gramme. 

NOTE  (11,)  p.  28. 

COMPOSITION   OF   STARCH,  d 


Strecker.* 


Carbon 
Hydrogen 
Oxygen     , 


Carbon  . 

Hydrogen 

Oxygen 


Carbon  . 
Hydrogen 
Oxygen  . 


Calculated 
P.12H10O10. 
44.91 

6-11 

48-98 

From 
Peas. 

44-33 
6-57 
49-09 

From 
Lentils. 

44-46 
6-54 
49-00 

From 
Beans. 

44-16 
6-69 
49-15 

From 
Buckwheat. 

44-23 
6-40 
49-37 

Strecker.* 


B  rom  maize.  From  horse-chestnuts.  From  wheat.  From  rye. 

44-16 


44-27 

6-67 

49-06 


44-44 

6-47 

49-08 

Strecker.* 


44-26 
6-70 
49-04 


6-64 
49-20 


From  rice. 

44-69 
6-36 
48-95 
From  potatoes 


From 
dahlia-roots. 

44-13 
6-56 
49-31 


From 
unripe  apples. 

44-10 
6-57 
49-33 


From 
unripe  pears. 

44-14 
6-75 
49-11 


From  arrow-root.    From  yams.a 


Berzelius.  Gay  Lussac  &  Thenard.  Prout.  Ortigosa, 

Carbon    .        44-250  43-55  44-40  44-2 

Hydrogen    .      6-674  6-77  6-18  6-5 

Oxygen   .        49-076  49-68  49-42  49-3 

n  The  starch  employed  for  the  analyses,  made  by  Strecker  and  Ortigosa,  was  prepared  from  the 
chemical  laboratory  at  Giessen,  from  the  respective  seeds,  bulbs,  and  fruits. 


NOTE  (12,)  p.  28. 

COMPOSITION   OF    GRAPE    SUGAR.      (STARCH   SUGAR.) 

From  grapes. a    From  starch.6    From  honey .c 

Prout. 


grapes. a 

De  Saussure. 


Calculated. 
C12H14014. 


Carbon      .        36-71  37-29  36-36  36-80 

Hydrogen      .      678  6-84  7-09  7-01 

Oxygen      .        56-51  55-87  56-55  56-19 

a  \nu.  de  Chimie,  XL,  391.    6  Ann.  of  Philosophy,  VI.,  426.    c  Philosoph.  Trans.  1827,  373. 


APPENDIX.— ANALYTICAL    EVIDENCE. 
NOTE  (13,)  p.  29. 


COMPOSITION  OF    SUGAR    OF   MILK. 

Gay  Lussac 
and  Thenard.      Prout.        Brunn.        Berzelius.        Liebig.' 

Carbon  .    38-825      40-00    40-437      39-474      40-00 
Hydrogen     7-341        6-66      6-711        7-167 
Oxygen.    53-834      53-34    52-852     53-359 


Gay  Lussac 
and  Thenard. 

Carbon  •  42-23 
Hydrogen  6-93 
Oxygen  •  50-84 


NOTE  (14,)  p.  29. 

COMPOSITION   OF    GUM. 


Goebel. 

42-2 

6-6 

51-2 


Berzelius. 

42-682 

6-374 

50-944 


Calculated 
C12H12O12. 

40-46 

6-73         6-61 
53.27       52-93 


Calculated. 
C12H11O11. 

42-58 

6-37 

51-05 


NOTE  (15,)  p.  29. 
ANALYSIS  OF  OATS.   (Boussingault.)  a. 
100  parts  of  oats  contain  of  dry  matter    . 
Ditto  water 


82-9 
17-1 


100-0 

100  parts  of  oats  dried  at  212°  =  1 177  parts  dried  at  the  ordinary  temperature  contain 
Carbon  -  V  '  ,  50-7 
Hydrogen  .  .  6-4 
Oxygen  .  .  36-7 
Nitrogen  .  .  2-2 
Ashes  .  .  4-0 


Water 


100-0 
17-7 


Oats  dried  in  the  air  1177  contain,  in  100  parts,  1-867  of  nitrogen. 
a  Ann.  de  Chiraie  et  de  Phys,,  LXXL,  130. 


ANALYSIS    OF   HAY. 


100  parts  of  hay  dried  in  the  air  contain  86  of  dry  matter, 

14  of  water. 


100 

100  parts  of  hay  dried  at  212°=  116-2  parts  dried  in  air,  contain 

Carbon            ,   '.•  >.        ,,  45-8 

Hydrogen      .        ;V*   •  5-0 

Oxygen               .          -V  387 

Nitrogen          .            .  1-5 

Ashes  9-0 


100-0 
16-2  water, 

116*2  hay  dried  in  the  air. 
100-0  of  hay  dried  at  the  ordinary  temperature  contain     1-29  of  nitrogen. 


240  oz.  of  such  hay=15  Ibs.  contain 
72  oz.  of  oats         =4^  Ibs.  contain 

Total 


3-095  oz.  of  nitrogen. 
1-34   •        ditto 


4-435 


ditto 


NOTE  (16,)  a,  p.  30. 

AMOUNT   OF    CARBON   IN    FLESH    AND    IN    STARCH. 

100  parts  of  starch  contain  44  of  carbon  ;  therefore,  64  oz.  (4  Ibs.)  contain  28-16  oz.  of 
carbon. 

100  parts  of  fresh  meat  contain  13-6  of  carbon  (see  Note  III.;)  hence  240  oz.  (15 
contain  32-64  oz.  of  carbon.* 


*  By  an  error  in  calculation  in  the  original,  the  amount  of  carbon  in  15  Ibs.  of  meat  is  stated  to  be 
27'64  oz.     It  follows,  that  the  carbon  of  4  Ibs.  of  starch  is  not  equal,  as  stated  in  the  text,  to  that  of 
15  Ibs.  of  flesh,  but  to  that  of  13  Ibs.     This  difference,  however,  is  not  sufficient  to  affect  the  argu 
went  at  p.  32. — EDITOR.  » 

12  H 


ANIMAL    CHEMISTRY. 
NOTE  (16,)  b,  P-  32. 

COMPOSITION    OF 


Hog's  Lard.           Mutton  fat.           Human  fat, 

Chevreul.  a 

Carbon    .    .    .  79-098               78-996 
Hydrogen  .     .     11-146                11-700 
Oxygen    ...    9756                 9-304 
a  Recherches  Chim.,  sur  les  Corps  Gras.    Paris. 

79-000 
11-416 
9-584 
1823. 

NOTE  (17,)  p.  32 

COMPOSITION   OF    CANE    SUGAR. 

According  to 
Be^eliu,    Prout.     W.  Crum.    LieLig.     < 

Carbon  42-225    42-86    42-14    42-301     42-47        42-58 

Hydrogen        6-600      6-35      6-42      6-384      6-90      '    6-37 
Oxygen          51-175     50-79    51-44    51-315    50-63        51-05 
Foi  the  composition  of  gum  and  of  starch,  see  Notes  (14)  and  (11) 

NOTE   (18,)  p.  32. 

COMPOSITION    OF    CHOLESTERINE. 

According  to 

Chevreul.  a    Couerbe.  6    Marchand.    Calculated 
C36H32O. 

Carbon  -  .        .      85-095      84-895      84-90      84-641 
Hydrogen      .          11-880      12-099      12-00      12-282 
Oxygen      .        .      3-025        3-006        3-10        3-077 
a  Recherches  sur  les  Corps  Gras,  p.  185.        b  Ann.  de  Ch.  et  de  Phys.  LVL,  p.  164, 


NOTE  (19,)  p.  33. 

THE    PRODUCTION   OF   WAX    FROM    SUGAR.* 

As  soon  as  the  bees  have  filled  their  stomach,  or  what  is  called  the  honey  bladder,  witfl, 
honey,  and  cannot  deposit  it  for  want  of  cells,  the  honey  passes  gradually  in  large  quan- 
tity into  the  intestinal  canal,  where  it  is  digested.  The  greater  part  is  expelled  as  excre 
ment ;  the  rest  enters  the  fluids  of  the  bee.  In  consequence  of  this  great  flow  of  juices 
a  fatty  substance  is  produced,  which  oozes  out  on  the  eight  spots  formerly  mentioned, 
which  occur  on  the  four  lower  Scales  of  the  abdominal  rings,  and  soon  nardens  into 
laminae  of  wax.  On  the  other  hand,  when  the  bees  can  deposit  their  honey,  only  so  much 
enters  the  intestinal  canal  as  is  necessary  for  their  support.  The  honey  bladder  need  not 
be  filled  with  honey  longer  than  forty  hours  in  order  to  bring  to  maturity,  on  the  eight 
spots,  eight  lamina?  of  wax,  so  that  the  latter  fall  off.  I  made  the  experiment  of  giving 
to  bees,  which  I  had  enclosed  in  a  box  with  their  queen  about  the  end  of  September,  dis- 
solved sugar  candy  instead  of  honey.  Out  of  this  food  laminae  of  wax  were  formed;  but 
these  would  not  separate  and  fall  off  readily,  so  that  the  mass,  which  continued  to  ooze 
out,  remained,  in  most  of  the  bees,  hanging  to  the  upper  laminae :  and  the  laminae  of  wax 
became  as  thick  as  four  under  ordinary  circumstances.  The  abdominal  scales  of  the  bees 
were,  by  means  of  the  wax,  distinctly  raised,  so  that  the  waxen  laminae  projected  between 
them.  On  examination,  I  found  that  these  thick  laminae,  which  under  the  microscope 
exhibited  several  lamellae,  had  a  sloping  surface  downwards  near  the  head,  and  upwards 
in  the  vicinity  of  the  tail.  The  first  waxen  laminae,  therefore,  must  have  been  pushed 
downwards  by  the  second,  because,  where  the  abdominal  scales  are  attached  to  the  skin, 
there  is  no  space  for  two  laminae,  the  second  by  the  third,  and  thus  the  inclined  surfaces 
on  the  sides  of  the  thick  laminae  had  been  produced.  I  saw  distinctly  from  this,  that  the 
first  formed  laminae  are  detached  by  those  which  followed.  The  sugar  had  been  converted 
into  wax  by  the  bees,  but  it  would  seem  that  there  was  some  imperfection  in  the  process, 
as  the  laminae  did  not  fall  off,  but  adhered  to  the  succeeding  ones. 

In  order  to  produce  wax  in  the  manner  described,  the  bees  require  no  pollen,  but  only 
honey.  I  have  placed,  even  in  October,  bees  in  an  empty  hive,  and  fed  them  with  honey  ; 
they  soon  formed  comb,  although  the  weather  was  such  that  they  could  not  leave  the 
hive.  I  cannot,  therefore,  believe  that  pollen  furnishes  food  for  the  bees,  but  I  think  they 
only  swallow  it,  in  order,  by  mixing  it  with  honey  and  water,  to  prepare  the  liquid  food 
for  the  grubs.  Besides,  bees  often  starve  in  April,  when  their  stock  of  honey  is  con- 
sumed, and  when  they  can  obtain  in  the  fields  abundance  of  pollen,  but  no  honey. 

*  From  F.  W.  Gundlach's  Natural  History  of  Bees,  p.  115.  Cassel,  1842  We  are  acquainted 
with  no  more  beautiful  or  convincing  proof  of  the  formation  of  fatty  matter  from  sugar  than  the  fol- 
lowing process  of  the  manufacture  of  wax  by  the  bees,  as  taken  from  observation. 


A  P  P  E  N  D  I  X.— A  N  A  L  Y  T I  C  A  L    EVIDENCE.  91 

When  pressed  by  hunger  they  tear  the  nymphae  out  of  the  cells,  and  gnaw  them  in  ordei 
to  support  life  by  the  sweet  juice  which  they  contain.  But,  if  in  this  condition  they  are 
not  artificially  fed,  or  if  the  fields  do  not  soon  yield  their  proper  food,  they  die  in  the  course 
of  a  few  days.  Now,  if  the  pollen  were  really  nourishment  for  bees,  they  ought  to  be 
able  to  support  life  on  it,  mixed  with  water. 

Bees  never  build  honeycomb  unless  they  have  a  queen,  or  are  provided  with  young  out 
of  which  they  can  educate  a  queen.  But  if  bees  be  shut  up  in  a  hive  without  a  queen, 
and  fed  with  honey,  we  can  perceive  in  forty-eight  hours  that  they  have  laminae  of  wax 
on  their  scales,  and  that  some  have  even  separated.  The  building  of  cells  is  therefoi  e 
voluntary,  and  dependent  on  certain  conditions,  but  the  oozing  out  of  wax  is  involuntary. 

One  might  suppose  that  a  large  proportion  of  these  laminae  must  be  lost,  since  the 
bees  may  allow  them  to  fall  off,  out  of  the  hive  as  well  as  in  it;  but  the  Creator  has 
wisely  provided  against  such  a  loss.  If  we  give  to  bees  engaged  in  building  cells  honey 
in  a  flat  dish,  and  cover  the  dish  with  perforated  paper,  that  the  bees  may  not  be  en- 
tangled in  the  honey,  we^hall  find,  after  a  day,  that  the  honey  has  disappeared,  and  that 
a  iarge  number  of  laminae  are  lying  on  the  paper.  It  would  appear  as  if  the  bees,  which 
nave  carried  off  the  honey,  had  let  fall  the  scales ;  but  it  is  not  so.  For,  if  above  the 
paper  we  lay  two  small  rods,  and  on  these  a  board,  overhanging  the  dish  on  every  side, 
so  that  the  bees  can  creep  under  the  board  and  obtain  the  honey,  we  shall  find  next  day 
ine  honey  gone,  but  no  laminae  on  the  paper ;  while  laminae  will  be  found  in  abundance 
on  me  board  above.  The  bees,  therefore,  which  go  for  and  bring  the  honey,  do  not  let 
fall  the  lamina?  of  wax,  but  only  those  bees  which  remain  hanging  to  the  top  of  the  hive. 
Repeated  experiments  of  this  kind  have  convinced  me  that  the  bees,  as  soon  as  their 
laminae  of  wax  are  mature,  return  to  the  hive  and  remain  at  rest,  just  as  caterpillars  do, 
when  about  to  change.  In  a  swarm  that  is  actively  employed  in  building  we  may  see 
thousands  of  bees  hanging  idly  at  the  top  of  the  hive.  These  are  all  bees  whose  laminse 
of  wax  are  about  to  separate.  When  they  have  fallen  off,  the  activity  of  the  bee  revives, 
and  its  place  is  occupied  for  the  same  purpose  by  another. 

^From  page  28  of  the  same  work.)  In  order  to  ascertain  how  much  honey  bees  re- 
quire to  form  wax,  and  how  often,  in  a  swarm  engaged  in  building,  the  laminae  attain 
maturity  and  fall  off,  I  made  the  following  experiment,  which  appears  to  me  not  unin- 
teiesting. 

On  the  29tn  of  August,  1841,  at  a  time  when  the  bees  could  obtain  in  this  district  no 
farther  supply  of  honey  from  the  fields,  I  emptied  a  small  hive,  placed  the  bees  in  a 
small  wooden  hive,  having  first  selected  the  queen  bee,  and  shut  her  up  in  a  box,  fur- 
nished with  wires,  which  I  placed  in  the  only  door  of  the  hive,  so  that  no  embryoes  could 
enter  the  cells.  I  then  placed  the  hive  in  a  window,  that  I  might  be  able  to  watch  it. 

At  6  P.  M.  I  gave  the  bees  6  oz.  of  honey  run  from  the  closed  cells,  which  had  thus 
the  exact  consistence  of  freshly  made  honey.  This  had  disappeared  next  morning.  In 
the  evening  of  the  30th  I  gave  the  bees  6  oz.  more,  which,  in  like  manner,  was  removed 
by  the  next  morning ;  but  already  some  laminae  of  wax  were  seen  lying  on  the  paper 
with  which  the  honey  was  covered.  On  the  31st  August  and  the  1st  September  the  bees 
had  in  the  evening  10  oz.,  and  on  the  3d  of  September  in  the  evening  7  oz.;  in  all,  there- 
fore, 1  Ib.  13  oz.  of  honey,  which  had  run  cold  out  of  cells  which  the  bees  had  already 
closed.  On  the  5th  of  September  I  stupified  the  bees,  by  means  of  puff-^all  and  counted 
them.  Their  number  was  2,765,  and  they  weighed  10  oz.  I  next  weighed  the  hive, 
the  combs  of  which  were  well  filled  with  honey,  but  the  cells  not  yet  closed;  noted  the 
weight,  and  then  allowed  the  honey  to  be  carried  off  by  a  strong  swarm  of  bees.  This 
was  completely  effected  in  a  few  Hours.  I  now  weighed  it  a  second  time,  and  found 
it  12  oz.  lighter;  consequently  the  bees  still  had  in  the  hive  12  oz.  of  the  29  oz.  of  honey 
given  to  them.  I  next  extracted  the  combs,  and  found  that  their  weight  was  f  of  an 
ounce.  I  then  placed  the  bees  in  another  box,  provided  with  empty  combs,  and  fed  them 
with  the  same  honey  as  before.  In  the  first  few  days  they  lost  daily  rather  more  than  1 
oz.  in  weight,  and  afterwards  half  an  ounce  daily,  which  was  owing  to  the  circumstance, 
that  from  the  digestion  of  so  much  honey,  their  intestinal  canal  was  loaded  with  excre- 
ments; for  1,170  bees,  in  autumn,  when  they  have  been  but  a  short  time  confined  to  the 
hive,  weigh  4  oz. ;  consequently  2,765  bees  should  weigh  9  oz.  But  they  actually  weighed 
10  oz.,  and  therefore  had  within  them  1  oz.  of  excrement,  for  their  honey  bladders  were 
empty.  During  the  night  the  weight  of  the  box  did  not  diminish  at  all,  because  the 
small  quantity  of  honev  the  bees  had  deposited  in  the  cells,  having  already  the  proper 
consistence,  could  not  lose  weight  by  evaporation,  and  because  the  bees  could  not  then 
get  rid  of  their  excrements.  For  this  reason,  the  loss  of  weight  occurred  always  during 
the  day. 

If,  then,  the  bees,  in  seven  days,  required  3£  oz.  of  honey  to  support  and  nourish  their 
bodies,  they  must  have  consumed  13£  oz.  of  honey  in  forming  f  of  an  ounce  of  wax; 
and  consequently,  to  form  1  Ib.  of  wax,  20  Ibs.  of  honey  are  required.  This  is  the  reason 
why  the  strongest  swarms  in  the  best  honey  seasons,  when  other  hives,  that  have  no 
occasion  to  build,  often  gain  in  one  day  3  or  4  Ibs.  in  weight,  hardly  become  heavier, 
although  their  activity  is  boundless.  All  that  they  gain  is  expended  in  making  wax 


92  ANIMAL   CHEMISTRY. 

This  is  a  hint  for  those  who  keep  bees,  to  limit  the  building  of  comb.  Cnauf  has  already 
recommended  this,  although  he  was  not  acquainted  with  the  true  relations  of  the  subject. 
From  1  oz.  of  wax,  bees  can  build  cells  enough  to  contain  1  Ib.  of  honey. 

100  laminae  of  wax  weigh  0*024  gramme  (rather  more  than  £  of  a  grain,)  consequently, 
1  kilogramme  (=  15,360  grains)  will  contain  4,166,666  laminae.  Hence,  f  of  an  ounce 
will  contain  81,367  laminae.  Now  this  quantity  was  produced  by  2,765  bees  in  six  days ; 
so  that  the  bee  requires  for  the  formation  of  its  8  laminae  (one  crop)  about  thirty-eight 
hours,  which  agrees  very  well  with  my  observations. 

The  laminae,  when  formed,  are  as  white  as  bleached  wax.  The  cells  also,  at  first,  are 
quite  white,  but  they  are  coloured  yellow  by  the  honey,  and  still  more  by  the  pollen. 
When  the  cold  weather  comes  on,  the  bees  retire  to  the  hive  under  the  honey,  and  live 
on  the  stock  they  have  accumulated. 

P.  54.  Many  believe  that  bees  are  hybernating  animals ;  but  the  opinion  is  quite  erro- 
neous. They  are  lively  throughout  the  winter ;  and  the  hive  is  always  warm  in  conse- 
quence of  the  heat  which  they  generate.  The  more  numerous  the  bees  in  a  hive,  the 
more  heat  is  developed  ;  and  hence  strong  hives  can  resist  the  most  intense  cold.  It  once 
happened  that  I  forgot  to  remove  from  the  door,  which  was  unusually  large,  of  a  hive 
in  winter,  a  perforated  plate  of  tinned  iron,  which  I  had  fastened  over  the  opening  to 
diminish  the  heat  in  July;  and  yet  this  hive  came  well  through  the  winter,  although  the 
cold  was  very  severe,  having  been  for  several  days  so  low  as  0°.  But  I  had  added  to 
this  hive  the  bees  of  two  other  hives !  When  the  cold  is  very  intense,  the  bees  begin  to 
hum.  By  this  means  respiration  is  accelerated  and  the  developement  of  heat  increased. 
If,  in  summer,  bees  without  a  queen  are  shut  up  in  a  glass  box,  they  become  uneasy  and 
begin  to  hum.  So  much  heat  is  by  this  means  developed,  that  the  plates  of  glass  become 
quite  hot.  If  the  door  be  not  opened  in  this  case,  or  if  air  be  not  admitted,  and  if  the 
glass  be  not  cooled  by  the  aid  of  water,  the  bees  are  soon  suffocated. 


Gay  Lussac  Calculated 

and  Thenard.a  De  Saussurc.6   Oppermann.o       Ettling.d  Hess.e          C20H20O. 

Carbon  .  81-784  81-607  81-291  81-15  81-52  81-38 
Hydrogen  .  12-672  13.859  14-073  13-75  13-23  13-28 
Oxygen  .  5-544  4-534  4-636  5-09  5-25  5-34 

a  Traite  de  Chimie,  par  M.  Thenard,  6me.  Ed.  TV.,  477. 

b  Ann.  de  Ch.  et  de  Phys.  XIII.,  310.    c  Ibid.  XLIX..,  224. 

d  Annal.  der  Pharm.,  II.,  267.    e  Ibid.  XX VII.,  6. 

NOTE  (21)  a,  p.  36. 

COMPOSITION  OF  HYDRATED  CYANURIC  ACID,  OR  HYDRATED  CYANIC  ACID,  AND  OF  CTAME- 
LIDE,  IN  100  PARTS,  ACCORDING  TO  THE  ANALYSIS  OF  WOHLER  AND  LIEBJG.*a 

Cyanuric  acid,  cyanic  acid,  cyamehde. 

Carbon 28-19 

Hydrogen 2-30 

Nitrogen .*•''•        32-63 

Oxygen 36-87 

a  Poggendorff's  Annalen,  XX.,  375  et  seq. 

NOTE  (21)  b.  p.  36. 

COMPOSITION  OF  ALDEHYDE,  METALDEHYDE,  AND  ELALDEHYDE.fl 

Aldehyde.         Metaldehyde.  Elaldehyde.  Calculated 

Liebig.*  Fehling.*  C4H4O2. 

Carbon               55-024        '54-511            54-620   »           54-467'  55-024 

Hydrogen      .      8-983           9-054             9-248                9-075  8-983 

Oxygen     .        35-993          36-435           36-132               36-458  35-993 

a  Ann.  der  Pharm.,  XIV.,  142,  und  XXVII.,  319. 

NOTE  (22,)  p.  37. 

COMPOSITION   OF    PROTEINE. 


Carbon 
Hydrogen 
Nitrogen 
Oxygen 

a  Ann.  der  Chem.  nnd  Pharm.,  XL..  43. 


From  the  crystalline  lens.    From  albumen. 
Scherer.a 

,  From  fibrine. 

• 

55-300 
6-940 
16-216 
21-544 

55-100 
7-055 
15-966 
21-819 

54-848 
6-959 
15-847 
22-346 

APPENDIX.— ANALYTICAL  EVIDENCE. 


93 


Scherer.a 


Carbon     . 
Hydrogen    . 
Nitrogen 
Oxygen 


Carbon     . 
Hydrogen 
Nitrogen 
Oxygen 


From  hair. 

From  horn.              C48H36N6O14, 

54-746 
7-129 
1-727 

22-398 

55-150 
7-197 
15-727 
21-926 

55-408 
7-238 
15-593 
21-761 

54-291 
7-082 
15-593 
23-034 

55-742 
6-827 
16-143 
21-228 

a  Ann.  der  Chem.  und  Pharm.,  XL.,  43. 


From  vegetable  albumen. 


From  fibrine.    From  albumen.    From  cheese. 
Mulder.a 


54-99 

55-44 

55-30 

55-159 

6-87 

8-95 

6-94 

7-176 

15-66 

16-05 

16-02 

15-857 

22-48 

21-56 

21-74 

21-808 

a  Ann.  de  Pharm.,  XXVIII.,  75. 


NOTE  (23,)  p.  37. 

COMPOSITION  OF  THE  ALBUMEN  OF  THE  YOLK  AND  OF  THE  WHITE  OF  THE  EGG.fl 


From  the  yolk. 
Jones.* 


53-72 

7-55 

13-60 


ir. 

53-45 
7-66 
13-34 


Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus 

a  Ann.  der  Chem.  und  Pharm.  XL.,  36,  ibid.  67. 


25-13 


25-55 


From  the  white. 
Scherer.* 


55-000 

7-073 

15-920 

22-007 


NOTE  (24,)  p.  38. 

COMPOSITION    OF   LACTIC    ACID. 

C6H5O5. 

Carbon        .  ....        44-90 

Hydrogen 6-11 

Oxygen 48-99 

NOTE  (25,)  p.  39. 

OAS  FROM  THE  ABDOMEN  OF  COWS  AFTER  EATING  CLOVER  TO  EXCESS,  OBTAWBD 

BY  PUNCTURE. 

a  Examined  by  Lameyran  and  Fr6my.     b  By  Vogel.    c  By  Pfliigs. 

Air.  Carbonic  acid.  Inflammable  gas.  Sulphuretted  hydrogen. 

a    5  5  —  15  80  Vol.  in  100  Vol. 

b  25  —  27  48  — 

c  —  —  60  40  — 

c  —  —  20  80 


NOTE  (26,)  p.  40. 

MAGENDIE  FOUND  IN  THE  STOMACH  AND  INTESTINES  OF  EXECUTED  CRIMINALS  : 

a  In  the  case  of  an  individual  who  had  taken  food  in  moderation  one  hour  previous  to 
death  ;  b,  in  the  case  of  one  who  had  done  so  two  hours  previously;  and  c,  in  the  casa 
of  a  third,  who  had  done  so  four  hours  previous  to  execution. 

100  Volumes  of  the  gas  contained: 
Oxygen.          Nitrogen.     Carbonic  acid.     Inflammable  gas. 

TFrom  the  stomach             11-00  Vol.  71-45  14-00  3-55 

a -2      —        small  intestines  00-00  20-03  24-39  55-53 

£      —        large  intestines  00-00  51-03  43-50  5-47 

rFrom  the  stomach             00-00  00-00  00-00  00-00 

b3      —        small  intestines  00-00  8-85  40-00  51-15 

(.      —        large  intestines  00-00  18-40  70-00  11-60 

TFrom  the  stomach             00-00  00-00  00-00  00-00 

cl      —        small  intestines  00-00  66-60  25-00  8-40 

(      _        large  intestines  00-00  45-96  42-86  11-18 


i 


94  ANIMAL   CHEMISTRY. 

NOTE  (27,)  referred  to  in  NOTE  (7,)  p.  21. 

COMPOSITION  OF  ANIMAL  ALBUMEN  AND  FIBRINE,  AND  OF  THE  DIFFERENT 
TISSUES  OF  THE  BODY. 
1.  ALBUMEN. 

From  eggs. 


From  the  serum  of  blood. 

Scherer.*o 


From  yolk  of  egg. 
Jones  ,*b 


Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus  J 


Carbon    . 

Hydrogen  . 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus 


}' 


53-850 
6-983 
15-673 

ii. 
55-461 
7-201 
15-673 

in. 

55-097 
6-880 
15-681 

55-000 
7-073 
15-920 

53-72 
7.55 
13-60 

VI. 

53-45 
7-66 
13-34 

23-494 

21-655 

22-342 

22-007 

25-13 

25-55 

nn.  der  Chem.  und  Pharm.,  XL.,  36. 

6  Ibid. 

67. 

Jones.* 

From  albumen 
of  brain. 

VII. 

55-50 
.      7-19 
16-31 

Scherer.* 

From 

hyclrocele. 

VIII. 

54-921 
7-077 
15-465 

From  congestive 
abscess.                From  pus. 

From  fluid 
of  dropsy 

XII 

54-302 
7-176 
15-717 

IX. 

54-757 
7-177 

15-848 

54-663 
7-022 
15-839 

54-101 
6-947 
15-660 

.    21-00 

22-537 

22-224 

22-476 

23-292 

22-805 

Mulder.* 

54-84 
,      7-09 
15-83 
,    21-23 

l_ 

rogen  . 

• 

•        • 

Carbon 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus 


Sulphur  ....    -*?•*'• ;•*•'•       0-68 
Phosphorus         .        .        .        .  0-33 

a  Ann.  der  Pharm.  XXVIIL,  74. 

2.  FlBRINE. 

Scherer.'a 

T U.  U\. TV.  -V.  VL VII.  ' 

53-671     54.454    55-002    54-967    53-571     54-686    54-844 

6-878      7-069      7-216      6-867      6-895      6-835      7-219 

15-763    15-762    15-817    15-913    15-720    15-720    16-065 


23-688    22-715    21-965    22-244    23-814    22-759    21-872 

a  Ann.  der  Chem.  und  Pharm.,  XL.,  33. 

Carbon        .    :  y  k*  *     v.        54-56 

Hydrogen        ....      6-90 

Nitrogen       .        .        .        .        15.72 

Oxygen  ,        .        .        .    22-13 

Sulphur    .    v *  •' .        .        .         0-33 

Phosphorus     ....      0-36 

a  Ann.  der  Chem.  und  Pharm.,  XXVIIL,  74. 

3.  GELATINOUS  TISSUES. 

Scherer.*a 


Carbon 
Hydrogen 
Nitrogen 
Oxygen 

Isinglass. 

50-557 
6-903 
18-790 
23-750 

Tendons  of  the 
calf's  foot. 

Tunica                Calculated, 
sclerotica.        C48H41N7^O18 

49-563 
7-148 
18-470 
24.819 

50-960 
7-188 
18-320 
23-532 

50-774 
7-152 
18-320 
23-754 

50-995 
7-075 
18-723 
23-207 

50-207 
7-001 
18-170 
24-622 

a  Ann.  der  Chem.  und  Pharm.,  XL.,  46. 


Carbon 
Hydrogen   . 
Nitrogen 
Oxygen 


Mulder. 

'50-048  50-048 

6-477  6-643 

18-350  18-388 

25-125  24-921 


APPEND IX.- -ANALYTICAL    EVIDENCE. 


95 


4.    Tl««itJES  CONTAINING  CnONDRINE. 

Scherer.*a 


Carbon 
Hydrogen 
Nitrogen 
Oxvgen 


Oartilages  of  the 
ribs  of  th,e  calf. 

Calculated 
Cornea.    C48H40IV6O20 

49-522      50-745 
7-097        6-904 
14-399      14-692 
28-982      27-659 

49-496 
7-133 
41-908 
28-463 

50-895 
6-962 
14-908 
27-235 

Mulder. 

50-607 

6-578 

14-437 

28-378 


a  Ann.  der  Chem.  und  Pharm.,  XL.,  49. 


5.  COMPOSITION  OF  THE  MIDDLE  MEMBRANE  OP  ARTERIES. 

Scherer.*a 


Carbon 
Hydrogen 
Nitrogen 
Oxygen 


53-750 

7-079 

15-360 

23-811 


n. 
53-393 

6-973 
15-360 
24-274 


Calculated 
C48H38N6016 

53-91 

6-96 

15-60 

23-53 


a  Ann.  der  Chem.  und  Pharm.,  XL.,  51, 
6.  COMPOSITION  OP  HORNY  TISSUES. 

Scherer.*a 


External  skin 
of  the  sole  of  the  foot 

Hair  of 
the  beard. 

51-529 
6-687 
17-936 

Hair  of  the  head. 
Fair.          Brown. 

Black. 

hi  -036 
6-801 
17-225 

50-752 
6-761 
17-225 

&0-652 
6-769 
17-936 

49-345 
6-576 
17-936 

50-622 
6-613 
17-936 

49-9* 
6-631 
17:936 

24-938 

25-262 

23-848 

24-643 

26-143 

24-829 

25-498 

Schere 

T.*a 

Calculated 
J48H39N"O17 

51-718 
6-860 
17-469    . 

Buffalo  horn. 

Nails. 

51-089 
6-824 
16-901 

Wool.    C 

50-653 
7-029 
17-710 

51-990 
6-717 

17-284 

51-162 
6-597 

17-284 

51-620 
6-754 

17-284 

51-540 
6-779 
17-284 

24-009 

24-957 

24-342 

24-397 

25-186 

24-608 

23-953 

Carbon 
Hydrogen 
Nitrogen 
Oxygen  ? 
Sulphur  > 


Carbon 
^    Hydrogen 
Nitrogen 
Oxygen 
Sulphur 

a  Ann.  der  Chem.  und  Pharm.,  XL.,  53. 

The  composition  of  the  membrane  lining  the  interior  of  the  shell  of  the  egg  approaches 
closely  to  that  of  horn.    According  to  Scherer,  it  contains 

Scherer.*a 

Carbon 50-674 

Hydrogen        .        .        ...        .        .      6-608 

Nitrogen 16*761 

.  25-958 


a  Ann.  der  Chem.  und  Pharm.,  XL.,  60. 
The  composition  of  feathers  is  also  nearly  the  same  as  that  of  horn. 


Scherer.*a 


Carbon 
Hydrogen 
Nitrogen 
Oxygen 


Beard  of  the 
feather. 

.  .  50-434 
-  .  '  .  7-110 

.  .  17-682 
.  .  24-774 
a  Ann.  der  Chem.  und  Pharm.,  XL.,  61. 


Quill  of  the 
feather. 

52-427 

7-213 

17-893 

22-467 


Calculated 
C48H39N7O16. 

52-457 

6-958 

17-719 

22-866 


The  analysis  here  given  of  the  beard  of  feathers  agrees  closely  with  that  of  horn,  while 
that  of  the  quill  is  more  accurately  represented  by  the  attached  formula,  which  differs 
from  *hat  of  horn  by  1  eq.  of  oxygen  only. 

7.  COMPOSITION  OP  THE  PIGMENTUM  NIGRUM  OCULI. 


Scherer.*et 


Carbon 
Hydrogen 
Nitrogen 
Oxygen 


58-273 

5973 

13-768 

21-986 


58-673 

5-962 

13-768 

21-598 


57-908 

5-817 

13-768 

22-507 


a  Ann.  der  Chem.  und  Pharm.,  XL.,  63. 


ANIMAL   CHEMISTRY. 

NOTE  (28,)  p.  44. 

According  to  the  analyses  of  Playfair  and  Boeckmann, 
0-452  parts  of  dry  muscular  flesh  gave  0-836  of  carbonic  acid. 
0-407         ......    0-279  of  water. 

0-242      ......        0-450  of  carb.  acid  and  0-164  water. 

0191          ......    0-360        .        .        .     0-130 

0-305  of  dried  blood  gave  0-575  carbonic  acid  and  0-202  of  water. 
0-214         .        .        .        0-402        .        .        .      0-138 
]  -471  of  dried  blood,  when  calcined,  left  0-065  of  ashes=4-42  pr.  cent 
The  dried  flesh  was  found  to  contain          of  ashes    4-23  pr.  cent. 
The  nitrogen  was  found  to  be  to  the  carbon  as  1  to  8  in  equivalents. 

Hence 
Flesh  (beef.)  Ox-blood.  Blood. 

Playfair.        Bceckmann.        Playfair.        Boeckmann.        Mean  of  2  analyses. 

Carbon               51-83  51-89          51-95  51-96  51-96 

Hydrogen             7-57  7-59           7-17  7-33  7-25 

Nitrogen              15-01  15-05          15-07  15-08  15-07 

Oxygen              21-37  21-24         21-39  21-21  21-30 

Ashes                   4-23  4-23,         4-42  4-42  4-42 
Deducting  the  ashes,  or  inorganic  matter,  the  composition  of  the  organic  part  is, 

Carbon     .        .  .        54-12        54-18  54-19  54-20 

Hydrogen    .        .  .      7-89         7-93  7-48  7-65 

Nitrogen           .  .        15-67        15-71  15-72  15-73 

Oxygen        .        .  .    22-32        22-18  22-31  22-12 

This  corresponds  to  the  formula 

C48        .        .....  54-62 

H39           ......  7-24 

N«                 .....  15-81 

O15            ......  22-33 

NOTE  (29,)  p.  44. 

COMPOSITION  OP  CHOLEIC  ACID,  a 

Calculated 
Demargay.  Dumas.  C76H66N3O22. 

Carbon           .        .    63707  63-5  63-24 

Hydrogen  .        .         8-821  9-3  8-97 

•  .      Nitrogen         .        .      3-255  3-3  3-86 

Oxygen  .        .        24.217  23-9  23-95 

a  Ann.  der  Pharm.,  XXVII.,  284  and  293. 


NOTE  (30,)  p.  44. 

COMPOSITION   OF   TAURINE   AND    OP    CHOLOIDIC    ACID. 

1.  TAFRINE.  a 


Calculated. 


Demargay.*  Dumas.  C4H7NO!0 


Carbon           .        .    19-24                   19-26  19-48 

Hydrogen  .        .          5-78                     5-66  5-57 

Nitrogen         .        .     11-29                   11.19  11-27 

Oxygen       .        .        63-69                  63-89  63-68 
a  Ann.  der  Pharm.,  XXVII.,  287  and  292. 

2.  CHOLOIDIC  ACID,  a 

Demargay.* 

A .  Dumas.  Calculated. 

I.  jl      *  C36H56012 

Carbon           .        .    73-301               73-522               73-3  74-4 

Hydrogen        '  .         9-511                 9-577                 9-7  9-4 

Oxygen         .        .    17-188               16-901               17-0  162 

a  Ann.  der  Fharm.,  XXVII.,  289  and  293. 

In  reference  to  the  researches  of  Demargay  on  the  bile  I  would  make  the  following  ob- 
servations. 

The  matter  to  which  I  have  given  the  name  of  ckoleic  acid  is  the  bile  itself  separated 
from  the  inorganic  constituents  (salts,  soda,  &c.)  which  it  contains.  By  the  action  of 
subacetate  of  lead  aided  by  ammonia,  all  the  organic  constituents  of  the  bile  are  made  to 
unite  with  oxide  of  lead,  with  which  they  form  an  insoluble,  resinous  precipitate.  The 


APPENDIX.— ANALYTICAL   EVIDENCE.  97 

substance  here  combined  with  oxide  of  lead  contains  all  the  carbon  and  nitrogen  of  the 
bile.  The  substance  which  I  have  named  choloidic  acid  is  that  which  is  obtained,,  when 
the  bile,  purified  by  alcohol  from  the  substances  insoluble  in  that  fluid,  is  boiled  for  some 
time  with  an  excess  of  muriatic  acid.  It  contains  all  the  carbon  and  hydrogen  of  the 
bile,  except  those  portion  which  have  separated  in  the  form  of  taurine  and  ammonia. 
The  cholic  acid  contains  the  elements  of  bile,  minus  those  of  carbonate  of  ammonia. 

These  three  compounds,  therefore,  contain  the  products  of  the  metamorphosis  of  the 
entire  bile;  their  formulae  express  the  amount  of  the  elements  of  the  constituents  of  the 
bile.  No  one  of  them  exists  ready  formed  in  the  bile  in  the  shape  in  which  we  obtain  it; 
their  elements  are  combined  in  a  different  way  from  that  in  which  they  were  united  in  the 
bile ;  but  the  way  in  which  these  elements  are  arranged  has  not  the  slightest  inflence  on 
the  determination  by  analysis  of  the  relative  proportions  of  the  elements.  In  the  formulae 
themselves,  therefore,  is  involved  no  hypothesis ;  they  are  simply  expressions  of  the  re- 
sults of  analysis.  It  signifies  nothing  that  the  choleic  or  choloidic  acids  may  be  composed 
of  several  compounds  united  together.  No  matter  how  many  such  they  may  contain,  the 
relative  proportions  of  all  the  elements  taken  together  is  expressed  by  the  formula  which 
is  derived  from  the  analysis. 

The  study  of  the  products  which  are  produced  from  the  bile  by  the  action  of  the  at- 
mosphere, or  of  chemical  re-agents,  may  be  of  importance  in  reference  to  certain  patholo- 
gical conditions ;  but  except  as  concerns  the  general  character  of  the  bile,  the  knowledge 
of  these  products  is  of  no  value  to  the  physiologist;  it  is  only  a  burthen  which  impedes 
his  progress.  It  cannot  be  maintained  of  any  one  of  the  38  or  40  substances,  into  which 
ihe  bile  has  been  divided  or  split  up,  that  it  exists  ready  formed  in  the  healthy  secretion ; 
on  the  contrary,  we  know  with  certainty  that  most  of  them  are  mere  products  of  the  action 
of  the  re-agents  which  are  made  to  act  on  the  bile. 

The  bile  contains  soda;  but  it  is  a  most  remarkable  and  singular  compound  of  soda. 
When  we  cause  that  part  of  the  bile  which  dissolves  in  alcohol  (which  contains  nearly 
all  the  organic  part)  to  combine  with  oxide  of  lead,  thus  separating  the  soda,  and  then 
remove  the  oxide  of  lead,  we  obtain  a  substance,  choleic  acid,  which,  when  placed  in 
contact  with  soda,  forms  a  compound  similar  to  bile  in  its  taste;  but  it  is  no  longer  bile; 
for  bile  may  be  mixed  with  organic  acids,  nay,  even  with  dilute  mineral  acids,  without 
becoming  turbid  or  yielding  a  precipitate;  while  the  new  compound,  choleate  of  soda,  is 
decomposed  by  the  feeblest  acids,  the  whole  of  the  choleic  acid  being  separated.  Hence, 
bile  cannot  be  considered,  in  any  sense,  as  choleate  of  soda.  Further,  it  may  be  asked, 
in  what  form  are  the  cholesterine^  and  stearic,  and  margaric  acids,  which  are  found  in 
bile,  contained  in  that  fluid  ?  Cholesterine  is  insoluble  in  water,  and  not  saponifiable  by 
alkalies ;  and  if  the  two  fatty  acids  just  named  were  really  present  in  the  bile  as  soaps  of 
soda,  they  would  be  instantly  separated  by  other  acids.  Yet  diluted  acids  cause  no  such 
separation  of  stearic  and  margaric  acids  in  bile. 

It  is  possible  that,  in  the  course  of  new  and  repeated  investigations,  the  composition  of 
the  substances  obtained  from  bile  may  be  found  different  from  that  which  has  been  given 
in  our  analytical  developement  of  this  subject.  But  this,  if  it  should  happen,  can  have 
but  little  effect  on  our  formuke;  if  the  relative  proportions  of  carbon  and  nitrogen  be  not 
changed,  the  differences  will  be  confined  to  the  proportions  of  oxygen  and  hydrogen.  In 
that  case  it  will  be  necessary  for  the  developement  of  our  views  in  formulae,  only  to  assume 
that  more  water  and  oxygen,  or  less  water  and  oxygen,  have  taken  a  share  in  the  meta- 
morphosis of  the  tissues;  but  the  truth  of  the  developement  of  the  process  itself  will  not 
be  by  this  means  affected. 

NOTE  (31,)  p.  44. 

COMPOSITION   OP    CHOLIC    ACID,  a 

Dumas.  Calculated  C74H60018. 

Carbon  ....  68-5  .  .  .  68-9 
Hydrogen  ...  9.7  ...  9.2 
Oxygen  .  .  .  .21.8  .  .  .21.9 

a  Ann.  der  Pharm.  XXVII.,  295. 
NOTE  (32,)  p.  45. 

COMPOSITION   OP   THE    CHIEF    CONSTITUENTS    OF   THE   URINE    OF   MEN   AND   ANIMALS. 

1.  URIC  ACID. 

Liebig.*a  Mitsdierlich.6    Calculated  C10H4N4O6. 

Carbon      .  .        36-083  35-82  36-00 

Hydrogen  .        .      2-441  2-38  23-6 

Nitrogen    .  .        33-361  34-60  33.37 

Oxygen  .        .    28.126  27-20  28-27 

a  Ann.  der  Pharm.,  X.,  47. 
6  Poggendorff's  Ann.,  XXXIIL,  335. 
13 


ANIMAL   CHEMISTRY. 
2.  ALLOXAN.  a 

A  PRODUCT  OF  THE  OXIDATION  OP  URIC  ACID. 


Wcehler  and  Liebig.* 


Calculated  C8H4N2O1*. 


Carbon  . 
Hydrogen 
Nitrogen 
Oxygen 

.  30-38                   30-18 
2-57                    2-48 
.  17.96                   17-96 
.      49-09                  49-38 

30-34 
2-47 
17-55 
49.64 

a  Ann.  der  Pharm.,  XXVI.,  260. 

3.  UREA. 

III  '  - 

Prout.  o                           Wcehler  and  Liebig. 

b     Calculated  C2H4N2OS 

Carbon 
Hydrogen 
Nitrogen 
Oxygen 

19-99                             20-02 
6-65                                6-71 
.    46-65                              46-73 
I  .       26-63                              26-54 

20-192 
6-595 
46-782 
26-425 

a  Thompson's  Annals.,  XI.,  352. 
b  Poggend.  Ann.,  XX.,  375. 

4.  CRYSTALLIZED  HIPPURIC  ACID. 

Liebig.*  a             Dumas,  b            Mitscherlich.  c 

Calculated  C18H8NO5 

Carbon 
Hydrogen 
Nitrogen 
Oxygen 

60-742           60-5              60-63 
4-959             4-9                 4-98 
7-816            7-7                7-90 
26-483           26-9              26-49 

60-76 
4-92 
7-82 
26-50 

a  Ann.  der  Pharm.,  XII.,  20. 
b  Ann.  de  Ch.  et  de  Phys.,  LVIL, 
c  Poggend.  Ann.,  XXXIII.,  335. 

327.      /      .          / 

5.  ALLANTOINE.  a 

W«h!er  aud  Liehig.» 

Calculated  C8H6N406 

Carbon  . 
Hydrogen 
Nitrogen 
Oxygen 

.    30.60 
.        .        .         3-83 
.    35-45 
.       .        .       30-12 

30-66 
3-75 
35-50 
30-09 

a  Ann.  der  Pharm.,  XXVL,  215. 

6.  URIC  ON  XANTHIC  OXIDE,  a 

Wahler  and  Liebig.* 

Calculated  C5H2N2O2. 

Carbon 
Hydrogen 
Nitrogen 
Oxygen  . 

.    39-28 
.        .         2-95 
.    36-35 
...       .       21-24 

39-86 
2-60 
37-72 
20-82 

a  Ann.  der  Pharm.,  XX  VI.,  344. 

7.  CYSTIC  OXIDE,  a 

Thaulow.*                             Calculated  C6H6NO4S4. 

Carbon 
Hydrogen 
Nitrogen 
Oxygen  . 
Su  phur 

.        ,        .        .    30-01 
5-10 
.    11-00 
.        28-38 
.    25-51 

30-31 
4-94 
11-70 
26-47 
26-58 

a  Ann  der  Pharm.,  XXVII.,  200. 


APPENDIX.— ANALYTICAL   EVIDENCE. 


99 


The  cystic  oxide  is  distinguished  from  all  the  other  concretions  occurring  in  the  uri- 
nary bladder7  by  the  sulphur  it  contains.  It  can  be  shown  with  certainty,  that  the  sul- 
phur is  present  neither  in  the  oxidized  state,  nor  in  combination  with  cyanogen ;  and  in 
regard  to  its  origin  the  remark  is  not  without  interest,  that  four  atoms  of  cystic  oxide 
contain  the  elements  of  uric  acid ;  benzoic  acid,  sulphuretted  hydrogen,  and  water  j  all 
of  which  are  substances,  the  occurrence  of  which  in  the  body  is  beyond  all  doubt 


1  atom  uric  acid  .  .  . 
1  atom  benzoic  acid 
8  atoms  sulphuret-  > 
ted  hydrogen.  .  .  >" 

C10N4H406 

C14    H*O3 
H8    S8 
H7O7 

4  atoms  cystic  oxide  =  C^N'H^O^S8  =4  (C«NH604S2). 

An  excellent  method  of  detecting  the  preserfce  of  cystic  oxide  in  calculi  or  gravel  is 
the  following : 

The  calculus  is  dissolved  in  a  strong  solution  of  caustic  potash,  and  to  the  solution  is 
added  so  much  of  a  solution  of  acetate  of  lead,  that  all  the  oxide  of  lead  is  retained  in  so- 
lution. When  this  mixture  is  boiled  there  is  formed  a  black  precipitate  of  sulphuret  of 
lead,  which  gives  to  the  liquid  the  aspect  of  ink.  Abundance  of  ammonia  is  also  disen- 
gaged ;  and  the  alkaline  fluid  is  found  to  contain,  among  other  products,  oxalic  acid. 


NOTE  (33,)  p.  45. 

COMPOSITION"   OP   OXALIC,    OXALURIC,  AND    PARABANIC    ACIDS. 

1.  OXALIC  ACID  (hydrated.) 


Carbon  , 
Hydrogen 
Oxygen, 


Carbon 
Hydrogen 
Nitrogen 
Oxvgen 


Carbon 
Hydrogen 
Nitrogen 
Oxygen 


Gay  Lussac  &  Thenard. 

26-566 

.      2-745 

70-689 


Berthollet. 

25-13 
3-09 

71-78 


2.  OXALURIC  ACID,  a 

Woehler  and  Liebig.* 

27-600  27-318 

•  3-122  3-072 

21-218  21-218 

.  48-060  48-392 

a  Ann.  der  Pharm.,  XXVI.,  286. 

3.  PARABANIC  ACID,  a 

Woehler  and  Liebig.* 


31-940 

.      2-09  1-876 

24-66  24-650 

.    41-30  41-534 

a  Ann.  de  Pharm.,  XXVI.,  286. 


Calculated 
C2  O3+HO 

26-66 

2-22 

71-12 


Calculated 
C6H4N2O8 

27-59 

3-00 

21-29 

48-12 


31-91 
1-73 

24-62 
4174 


Hence— 


NOTE  (34,)  p.  45. 

COMPOSITION   OF    ROASTED   FLESH. 

(1.)  0-307  of  flesh  gave  0-584  of  carbonic  acid  and  0-206  of  water. 
(2.)  0-255        do.  0-485  do.  0-181         do. 

3.)  0-179        do.  0340  do.  0-125        do. 


Carbon 

Hydrogen 

Nitrogen 


Oxygen  > 


Ashes 


Flesh  of  roedeer(l.) 
Bceckmann.* 

52-60 

.      7-45 

15-23 

,    24-72 


Flesh  of  Beef  (2. )    Flesh  of  Teal  (3.) 
Playfair. 


52-590 

7-886 

15-214 

24.310 


42-52 

7-87 

14-70 

24.91 


100  ANIMAL   CHEMISTRY. 

/ 

NOTE  (35,)  p.  46. 

The  formula  C^HWO40,  or  C^HWO20,  gives,  when  reduced  to  100  parts, 
C64  ....        50-07 

H42  .  .  ...      6-35 

N9  19-32 

O«> 24-26 

Compare  this  with  the  composition  of  gelatine,  as  given  in  Note  (27) 


NOTE  (37,)  p.  49. 

COMPOSITION    OF   DITHOFELLIC    ACID.fl 

Ettling  and  Will.*  Wcehler.* 


Calculated 
C40H36O8 


Carbon        .        .        7H9        70-80        70-23        70-83        70-83 
Hydrogen        .        .     10-85        1078        10-95        10-60        10-48 
Oxygen       .        .        17-96        18-42        18-82        18-57        18-69 
a  Annalen  der  Chem.  und  Pharm.,  XXXIX.,  242,  and  XLL,  154. 


NOTE  (38,)  p.  56. 

COMPOSITION   OF   SOLANINE   FROM   THE    BUDS    OF    GERMINATING   POTATOES, 

Blanchet. 

Carbon 62-11 

Hydrogen 8-92 

Nitrogen 1'64 

Oxygen 27-33 

a  Ann.  der  Pharra.,  VII.,  150. 


NOTE  (39,)  p.  56. 

COMPOSITION  OF   PICROTOXINE.  O 

Francis.* 

Carbon.        ...        .        .        .    60-26 

Hydrogen 5-70 

Nitrogen        .        ;        .        .        .1-30 
Oxygen 32-74 

o  In  another  analysis.  M.  Francis  obtained  0'75  per  cent,  of  nitrogen.  The  picrotoxine  employed 
for  these  analyses  was  partly  obtained  from  the  manufactory  of  M.  Merck,  in  Darmstadt,  and  was 
partly  prepared  by  M.  Francis  himself;  it  was  perfectly  white,  and  beautifully  crystallized.  Reg- 
nault,  as  is  well  known,  found  no  nitrogen  in  this  compound. 

NOTE  (40,)  p.  56. 

COMPOSITION    OF    Q.UININE. 


Carbon 
Hydrogen 
Nitrogen   . 
Oxygen 

Liebig.* 

,    75-76 
7-52 
.      8-11 
8-62 

Calculated 
C20H12N02. 

74-39 
7-25 
8-52 
9-64 

NOTE  (41,)  p.  156. 

COMPOSITION   OF  MORPHIA,  rt 


Liebig.* 


Regnault. 


Calculated 
C35H20N06 


Carbon    .        .        .    72-340        72-87        72-41  72-28 

Hydrogen    .        .         6-366         6-86         6-84  6-74 

Nitrogen.        .        .      4-995          5-01          5-01  4-80 

Oxygen       .        .        16-299        15-26        15-74  16-18 
a  Ann.  der  Pharm.,  XXVI.,  23. 


APPENDIX.— ANALYTICAL   EVIDENCE.  101 

NOTE  (42,)  p.  156. 

COMPOSITION   OF    CAFFEINE,,   THEINE,    GUARANINE,    THEOBROMINE,    AND   ASPARAGINE. 

Caffeine,  a        Theine.  ft        Guaranine.  c        Calculated 
Pfaff  and  Liebig.*      Jobst.  Martius.          C8H5N2O2 

Carbon        .        .    49-77        50-101        49-679        49-798 

Hydrogen  .          5-33          5-214          5-139          5-082 
Nitrogen      .        .    28-78        29-009        29-180        28-832 

Oxygen    .  .        16-12        15-676        16-002        16-288 

a  Ann.  der  Pharm.,  I.,  17.  6  Ann.  der  Pharm.,  XXV.,  63.       c  Ann.  der  Pharm.,  XXVI.,  95 

Guaranine  is  the  name  given  to  the  crystallized  principle  of  the  guarana  officinalis,  tiLi 
ft  was  shown  to  be  identical  with  caffeine  and  theine,  as  the  above  analyses  demonstrate- 

COMPOSITION   OF   THEOBROMINE.  a 

Calculated 
Woskreseusky.  C9H5N302 

Carbon      .        .        .    47-21        46W        4671*  46-43 

Hydrogen     .'       .          4-53          4-61          4-52  4-20 

Nitrogen  .        .        .    35-38        35-38        35-38  35-85 

Oxyg-en         .        .        12-88        13-04        13-39  13-51 
a  Ann.  der  Chem.  und  Pharm.,  xli.,  125. 

COMPOSITION    O*     VSPARAGINE.fl 

Liebig.        Calculated  C8H8N206  +  2HO 

Carbon         .        .        .    iJ2-351  32-35 

Hydrogen.        .        .          0-844  6-60 

Nitrogen       ,        .        .     18-734  18-73 

Oxygeu    .        .        .        42-021  42-32 
a  Ann.  der  Pharm.,  VII.,  146. 

ON    THE    CONVERSION   OF   BENZOIC    ACID   INTO    HIPPURIC    ACID.*      BY  WILHELM  KELLER 

(From  the  Annalen  der  Chemie  und  Pharmacie.) 

So  early  as  in  the  edition  of  Berzelius*  "Lehrbuch  der  Chemie,"  published  in  1831, 
Professor  Wohler  had  expressed  the  opinion,  that  benzoic  acid,  during  digestion,  was 
probably  converted  into  hippuric  acid.  This  opinion  was  founded  on  an  experiment 
which  he  had  made  on  the  passage  of  benzoic  acid  into  the  urine.  He  found  in  the 
urine  of  a  dog  which  had  eaten  half  a  drachm  of  benzoic  acid  with  his  food,  an  acid  crys- 
tallizing in  needle-shaped  prisms,  which  had  the  general  properties  of  benzoic  acid,  and 
which  he  then  took  for  benzoic  acid.  (Tiedemann's  Zeitschrift  fur  Physiologie,  i.  142.) 
These  crystals  were  obviously  hippuric  acid,  as  plainly  appears  from  the  statements,  that 
they  had  the  aspect  of  nitre,  and,  when  sublimed,  left  a  residue  of  carbon.  But  at  that 
time  hippuric  acid  was  not  yet  discovered ;  and  it  is  well  known  that,  till  1829,  when 
these  acids  were  first  distinguished  from  each  other  by  Liebig,  it  was  uniformly  con- 
founded with  benzoic  acid. 

The  recently  published  statement  of  A.  Ure,  that  he  actually  found  hippuric  acid  in 
the  urine  of  a  patient  who  had  taken  benzoic  acid,  recalled  this  relation,  so  remarkable  in 
a  physiological  point  of  view,  and  induced  me  to  undertake  the  following  experiments, 
which,  at  the  suggestion  of  Professor  Wohler,  I  made  on  myself.  The  supposed  conver- 
sion of  benzoic  acid  into  hippuric  acid  has,  by  these  experiments,  been  unequivocally 
established. 

I  took,  in  the  evening  before  bed-time,  about  thirty-two  grains  of  pure  benzoic  acid  in 
syrup.  During  the  night  I  perspired  strongly,  which  was  probably  an  effect  of  the  acid, 
as  in  general  I  am  with  great  difficulty  made  to  transpire  profusely.  I  could  perceive  no 
other  effect,  even  when,  next  day,  I  took  the  same  dose  three  times;  indeed,  even  the 
perspiration  did  not  again  occur. 

The  urine  passed  in  the  morning  had  an  uncommonly  strong  acid  reaction,  even  aftei 
it  had  been  evaporated,  and  had  stood  for  twelve  hours.  It  deposited  only  the  usual  sedi- 
ment of  earthy  salts.  But  when  it  was  mixed  with  muriatic  acid,  and  allowed  to  stand, 

*  To  the  evidence  produced  by  A.  Ure,  of  the  conversion  of  benzoic  acid  into  hippuric  acid  in  the 
numan  body,  M.  Keller  has  added  some  very  decisive  proofs,  which  I  append  to  this  work  on  ac- 
count of  their  physiological  importance.  The  experiments  of  M.  Keller  were  made  in  the  laboratory 
of  Professor  Wohler,  at  Gottingen;  and  they  place  beyond  all  doubt  the  fact  that  a  non-azotized 
substance  taken  in  the  food  can  take  a  share,  by  means  of  its  elements,  in  the  act  of  transformation 
of  the  animal  tissues,  and  in  the  formation  of  a  secretion.  This  fact  throws  a  clear  light  on  the 
mode  of  action  of  the  greater  number  of  remedies  ;  and  if  the  influence  of  caffeine  on  the  formation 
of  urea  or  uric  acid  should  admit  of  being  demonstrated  in  a  similar  way,  we  shall  then  possess  the 
key  to  the  action  of  quinine  and  of  the  other  vegetable  alkalies. — J.  L. 


102  ANIMAL  CHEMISTRY. 

there  were  formed  in  it  long  prismatic,  brownish  crystals,  in  great  quantity,  which  even 
in  this  state,  could  not  be  taken  for  benzoic  acid.  Another  portion,  evaporated  to  the 
consistence  of  syrup,  formed,  when  mixed  with  muriatic  acid,  a  magma  of  crystalline 
scales.  The  crystalline  mass  was  pressed,  dissolved  in  hot  water,  treated  with  animal 
charcoal,  and  recrystallized.  By  this  means  the  acid  was  obtained  in  colourless  prisms, 
an  inch  in  length. 

Their  crystals  were  pure  hippuric  acid.  When  heated,  they  melted  easily;  and  when 
exposed  to  a  still  stronger  heat,  the  mass  was  carbonized,  with  a  smell  of  oil  of  bitter 
almonds,  while  benzoic  acid  sublimed.  To  remove  all  doubts,  I  determined  the  propor- 
tion of  carbon  in  the  crystals,  which  I  found  to  be  60-4  per  cent.  Crystallized  hippuric 
acid,  according  to  the  formula  C'WNO6-!-  HO,  contains  60*67  per  cent,  of  carbon;  crys- 
tallized benzoic  acid,  on  the  other  hand,  contains  69-10  per  cent,  of  carbon. 

As  long  as  I  continued  to  take  benzoic  acid,  I  was  able  easily  to  obtain  hippuric  acid  in 
large  quantity  from  the  urine;  and  since  the  benzoic  acid  seems  so  devoid  of  any  inju- 
rious effect  on  the  health,  it  would  be  easy  in  this  way  to  supply  one's  self  with  large 
quantities  of  hippuric  acid.  It  would  only  be  necessary  to  engage  a  person  to  continue 
for  some  weeks  this  new  species  of  manufacture. 

It  was  of  importance  to  examine  the  urine  which  contained  hippuric  acid,  in  reference 
to  the  two  normal  chief  constituents,  urea  and  uric  acid.  Both  were  contained  in  it,  and 
apparently  in  the  same  proportion  as  in  the  normal  urine. 

The  inspissated  urine,  after  the  hippuric  acid  had  been  separated  by  muriatic  acid 
yielded,  on  the  addition  of  nitric  acid,  a  large  quantity  of  nitrate  of  urea.  It  had  pre 
viously  deposited  a  powder,  the  solution  of  which  in  nitric  acid  gave,  when  evaporated 
to  dryness.  the  well-known  purple  colour  characteristic  of  uric  acid.  This  observation 
is  opposed  to  the  statement  of  Ure;  and  he  is  certainly  too  hasty  in  recommending  ben- 
zoic acid  as  a  remedy  for  the  gouty  and  calculous  concretions  of  uric  acid.  He  seems  to 
suppose  that  the  uric  acid  has  been  employed  in  the  conversion  of  benzoic  acid  into  hip- 
puric acid;  but  as  his  observations  were  made  on  a  gouty  patient,  it  may  be  supposed 
that  the  urine,  even  without  the  internal  use  of  benzoic  acid,  would  have  been  found  to 
contain  no  uric  acid.  Finally,  it  is  clear  that  the  hippuric  acid  existed  in  the  urine  in 
combination  with  a  base,  because  it  only  separated  after  the  addition  of  an  acid. 


THE  EK1X 


INDEX. 


A. 

A.cid,  Acetic.  Composition ;  and  relation  to  that 
of  aldehyde,  80,  81. 

Acid,  Benzoic.  Composition,  and  relation  to  that 
of  oil  of  bitter  almonds,  80,  8 1 .  Converted  into 
hippuric  acid  in  the  human  body,  48,  101. 

Acid,  Carbonic.  Is  the  form  in  which  the  in- 
spired oxygen  and  the  carbon  of  the  food  are 
given  out,  14.  Its  formation  in  the  body  the 
chief  source  of  animal  heat,  15 — 16.  Occurs 
combined  with  potash  and  soda,  in  the  serum 
of  the  blood,  21.  Formed  by  the  action  of 
oxygen  on  the  products  of  the  metamorphosis 
of  the  tissues,  26.  Its  formation  may  also  be 
connected  with  the  production  of  fat  from 
starch,  32 — 34.  Generated  by  putrefaction  of 
food  in  the  stomach  of  animals,  39.  Also  by 
the  fermentation  of  bad  wine  in  man,  when  it 
causes  death  by  penetrating  into  the  lungs,  39. 
Escapes  through  both  skin  and  lungs,  39.  Pro- 
duced, along  with  urea,  by  the  oxidation  of  uric 
acid,  45.  Produced  with  several  other  com- 
pounds, by  the  bxidation  of  blood,  45.  May 
be  formed,  along  with  choleic  acid,  from  hip- 
puric acid,  starch  and  oxygen,  49.  Also,  along 
with  choleic  acid,  urea,  and  ammonia,  by  the 
action  of  water  and  oxygen  on  staich  and  pro- 
teine,  49.  Produced,  along  with  fat  and  urea, 
from  proteine,  by  the  action  of  water  and  oxy- 
gen, in  the  absence  of  soda,  49.  Combines 
with  the  compound  of  iron  present  in  venous 
blood,  and  is  given  off  when  oxygen  is  ab- 
sorbed, 78.  Is  absorbed  by  the  serum  of  blood 
in  all  states,  78. 

Acid,  Cerebric.  Its  composition,  57.  Its  pro- 
perties, 58. 

Acid,  Choleic.  Represents  the  organic  portion 
of  the  bile,  44.  Its  formula,  44.  Its  trans- 
formations, 42.  Half  its  formula,  added  to  that 
of  urate  of  ammonia,  is  equal  to  the  formula  of 
blood  4~  a  little  oxygen  and  water,  44.  Pro- 
duced in  the  oxidation  of  blood,  45.  Views 
which  may  be  taken  of  its  composition,  47. 
May  be  formed  by  the  action  of  oxygen  and 
water  on  proteine  and  starch,  48.  Products 
of  its  oxidation,  49.  Various  ways  in  which 
it  may  be  supposed  to  be  formed  in  the  body, 
51.  Its  composition,  96.  Cannot  be  said  to 
exist  ready  formed  in  the  bile,  97. 

Acid,  Cholic.  Its  composition,  98.  Derived 
from  choleic  acid,  44.  Possible  relation  to 
choleic  acid,  47. 

Acid,  Choloidic.  Its  composition,  96.  Derived 
from  choleic  acid,  44.  Possible  relation  to 
choleic  acid,  47.  Possible  relation  to  starch,  51. 
Possible  relation  to  proteine,  46. 

Acid,  Cyanic.     Its  formula,  81. 

Acid,  Cyanuric.     Its  formula,  81. 

\cid,  Hippuric.  Its  composition,  98.  Appears 
in  the  urine  of  stall-fed  animals,  31.  Is  de- 
stroyed by  exercise,  31 ,  45.  Is  probably  formed  ; 


in  the  oxidation  of  blood,  45.  Is  found  in  the 
human  urine  after  benzoic  acid  has  been  ad- 
ministered, 48,  101.  May  be  derived  from  pro- 
teine when  acted  on  by  oxygen  and  uric  acid, 
48.  With  starch  and  oxygen,  it  may  produce 
choleic  and  carbonic  acids,  48.  May  be  derived 
from  the  oxidation  of  choleic  acid,  49. 

Acid,  Hydrocyanic  or  Prussic.  Its  poisonous  ac- 
tion explained,  80. 

Acid,  Lithofellic.  Its  composition,  100.  Probably 
derived  from  the  oxidation  of  choleic  acid :  is 
the  chief  constituent  of  bezoar  stones,  49. 

Acid,  Lactic.  Its  composition,  93.  Its  origin, 
38.  Does  not  exist  in  the  healthy  gastric 
juice,  38. 

Acid,  Margaric.     Exists  in  bile,  97. 

Acid,  Muriatic.  Exists  in  the  free  state  in  the 
gastric  juice,  37,  38.  Is  derived  from  common 
salt,  38,  52. 

Acid,  Oxaluric.     Analysis  of,  99. 

Acid,  Parabanic.     Analysis  of,  99. 

Acid,  Phosphoric.  Exists  in  the  urine  of  the 
carnivora  in  considerable  quantity,  30,  52.  Its 
proportion  very  small  in  that  of  the  gramini- 
vora,  31.  Derived  from  the  phosphorus  of  the 
tissues,  30.  It  is  retained  in  the  body  to  form 
bones  and  nervous  matter,  31. 

Acid,  Sulphuric.  Exists  in  the  urine  of  the  car- 
nivora, 30,  52.  Derived  from  the  sulphur  of 
the  tissues,  30. 

Acid,  Uric.  Its  composition,  98.  Products  of 
its  oxidation,  alloxan,  carbonic  acid,  oxalic  acid, 
urea,  &c.,  45.  Is  probably  derived,  along  with 
choleic  acid,  by  the  action  of  oxygen  and  water 
on  blood  or  muscle,  44.  Disappears  almost  en- 
tirely in  the  system  of  man  and  of  the  highei 
animals,  24,  41.  Appears  as  calculus,  when 
there  is  a  deficiency  of  oxygen,  44.  Never 
occurs  in  phthisical  cases,  45.  Yields  mulberry 
calculus  when  the  quantity  of  oxygen  is  some- 
what increased,  but  only  urea  and  carbonic  acid 
with  a  full  supply  of  oxygen,  45.  Uric  acid 
calculus  promoted  by  the  use  of  fat  and  of  cer- 
tain wines,  45.  Unknown  on  the  Rhine,  45. 
Uric  acid  and  urea,  how  related  to  allantoine, 
46;  to  gelatine,  46.  Forms  the  greater  part 
of  the  urine  of  serpents,  24.  Yields,  with  the 
elements  of  proteine  and  oxygen,  hippuric  acid 
and  urea,  48.  How  related  to  taurine,  49. 
Calculi  of  it  never  occur  in  wild  carnivora,  but 
often  in  men  who  use  little  animal  food,  47. 

Affinity,  Chemical.  Is  the  ultimate  cause  of  the 
vital  phenomena,  13.  Is  active  only  in  the 
case  of  contact,  and  depends  much  on  the  order 
in  which  the  particles  are  arranged,  62.  Its 
equilibrium  renders  a  compound  liable  to  trans- 
formations, 63.  In  producing  the  vital  pheno- 
mena, it  is  modified  by  other  forces,  63.  It  is 
not  alone  the  vital  force  or  vitality,  but  is  ex- 
erted in  subordination  to  that  force,  70. 

Air.     Introduced  into  the  stomach  during  digestion 

103 


104 


INDEX. 


with  the  saliva.  38.  Effects  of  its  temperature 
and  density,  dry  ness,  &c.,  in  respiration,  14,  15. 

Albumen.  Animal  and  vegetable  albumen  identi- 
cal, 22.  23.  Their  composition,  87,  93.  Ve- 
getable albumen,  how  obtained,  22.  Is  a  com- 
pound of  proteine,  and  in  organic  composition 
identical  with  fibrine  and  caseine,  36,  37.  Exists 
in  the  yolk  as  well  as  the  white  of  eggs,  37. 
Also  in  the  serum  of  the  blood,  21.  Is  the  true 
starting  point  of  all  the  animal  tissues,  37. 

Alcohol.  Is  hurtful  to  carnivorous  savages,  56. 
Its  mode  of  action :  checks  the  change  of  mat- 
ter, 72.  In  cold  climates  serves  as  an  element 
of  respiration,  16. 

Aldehyde.  Its  composition;  how  related  to  that 
of  acetic  acid,  80,  81. 

Alkalies.  Mineral  alkalies  essential  both  to  ve- 
getable and  animal  life,  52.  Vegetable  alkalies 
all  contain  nitrogen,  all  act  on  the  nervous  sys- 
tem, and  are  all  poisonous  in  a  moderate  dose, 
56,  57.  Theory  of  their  action :  they  take  a 
share  in  the  transformation  or  production  of 
nervous  matter,  for  which  they  are  adapted  by 
their  composition,  57 — 59.  Action  of  caustic 
alkalies  on  bile,  or  choleic  acid,  44. 

Allantoine.  Is  found  in  the  urine  of  the  fcetal 
calf.  How  derived  from  proteine.  How  re- 
lated to  uric  acid  and  urea,  46.  How  related 
to  choleic  acid,  47.  Its  composition,  98. 

Allen  and  Pepys.  Their  calculation  of  the  amount 
of  inspired  oxygen,  82. 

Alloxan.  Formed  by  the  oxidation  of  uric  acid, 
45.  Converted  by  oxidation  into  oxalic  acid 
and  urea/oxaluric  and  parabanic  acids,  or  car- 
bonic acid  and  urea,  45.  How  related  to  tau- 
rine,  50.  Seems  to  act  as  a  diuretic.  Recom- 
mended for  experiment  in  hepatic  diseases,  45. 
(note.) 

Almonds,  Bitter.  Oil  of.  Its  composition;  how 
related  to  benzoic  acid,  81. 

Ammonia.  Combined  with  uric  acid  it  forms  the 
urine  of  serpents,  birds,  &c.,  24.  Its  relation 
to  choleic,  choloidic,  and  cholic  acids,  44.  Is 
one  of  the  products  which  may  be  formed  by 
the  oxidation  of  blood,  45;  or  of  proteine,  48. 
Its  relation  to  uric  acid,  urea,  and  taurine,  49. 
To  allantoine  and  taurine,  49.  To  alloxan  and 
taurine,  49.  To  choleic  and  choloidic  acid  and 
taurine,  50.  To  urea,  water,  and  carbonic 
acid,  51.  Is  found  in  combination  with  acids 
in  the  urine  of  the  carnivora,  52. 

Analysis.  Of  dry  blood,  82,  96.  Of  dried  flesh, 
96.  Of  faeces,  83.  Of  black  bread,  83.  Of 
potatoes,  83.  Of  peas,  83.  Of  beans,  83.  Of 
lentils,  83.  Of  fresh  meat,  83.  Of  moist 
bread,  83.  Of  moist  potatoes,  83.  Of  the 
fibrine  and  albumen  of  blood,  87,  94.  Of  ve- 
getable fibrine  and  albumen,  vegetable  caseine 
and  gluten,  88.  Of  animal  caseine,  88.  Of 
starch,  88.  Of  grape  or  starch  sugar,  88.  Of 
sugar  of  milk,  89.  Of  gum,  89.  Of  oats,  89. 
Of  hay,  89.  Of  fat,  90.  Of  cane-sugar,  90. 
Of  cholesterine,  90.  Of  wax,  92.  Of  cyanic 
acid,  cyanuric  acid,  and  cyamelide,  92.  Of 
aldehyde,  metaldehyde,  and  elaldehyde,  92.  Of 
proteine,  93.  Of  albumen  from  the  yolk  and 
white  of  egg,  93.  Of  lactic  acid,  93.  Of  gas 
from  the  stomach  of  cows  after  eating  to  ex- 
cess, 93.  Of  gas  from  stomach  and  intestines 
of  executed  criminals,  93.  Of  gelatinous  tis- 
sues, 94.  Of  tissues  containing  chondrine,  95. 


Of  arterial  membrane,  95.  Of  horny  tissues, 
95.  Of  the  lining  membrane  of  the  egg,  95. 
Of  feathers,  95.  Of  the  pigmentum  nigrum,  95. 
Of  choleic  acid,  96.  Of  taurine,  96.  Of  cho- 
loidic acid,  96.  Of  cholic  acid,  98.  Of  uric 
acid,  98.  Of  alloxan,  98.  Of  urea,  98.  Of 
hippuric  acid,  98.  Of  allantoine,  98.  Ofxan 
thic  oxide,  99.  Of  cystic  oxide,  99.  Of  ox- 
alic acid,  99.  Of  oxaluric  acid,  99.  Of  para 
banic  acid,  99.  Of  roasted  flesh,  100.  Ot 
Jithofellic  acid,  100.  Of  solanine,  100.  Of 
picrotoxine,  100.  Of  quinine,  100.  Of  moi- 
phia,  101.  Of  caffeine,  theine,  or  guaranine, 
101.  Oftheobromine,101.  Of  asparagine,  101. 

Animal  Heat.  Derived  from  the  combination  of 
oxygen  with  the  carbon  and  hydrogen  of  the 
metamorphosed  tissues,  which  proceed  ulti- 
mately from  the  food,  15.  Is  highes-t  in  those 
animals  whose  respiration  is  most  active,  15. 
Is  the  same  in  man  in  all  climates,  15,  16.  Is 
kept  up  by  the  food  in  proportion  to  amount 
of  external  cooling,  16.  Is  not  produced  either 
by  any  direct  influence  of  the  nerves,  or  by 
muscular  contractions,  18,  19.  Its  amount  in 
man,  19.  Chemical  action  the  sole  source  of  it, 
20.  The  formation  of  fat  -from  starch  or  sugar 
must  produce  heat,  34.  The  elements  of  the 
bile,  by  combining  with  oxygen,  serve  chiefly 
to  produce  it,  26. 

Animal  Life.  Distinguished  from  vegetable  life 
by  the  absorption  of  oxygen,  and  the  produc- 
tion of  carbonic  acid,  11.  Must  not  be  con- 
founded with  consciousness,  12.  Conditions 
necessary  to  animal  life,  13,  14.  Depends  on 
an  equilibrium  between  waste  and  supply,  72, 
74,  75. 

Antiseptics.  They  act  by  putting  a  stop  to  fer- 
mentation, putrefaction,  or  other  forms  of  meta- 
morphosis, 54.  Their  action  on  wounds  and 
ulcers,  41. 

Arteries.  Composition  of  their  tunica  media,  95. 
How  derived  from  proteine,  42. 

Arterial  Blood.  Conveys  oxygen  to  every  part 
of  the  body,  26,  77.  Contains  a  compound  of 
iron,  most  probably  peroxide,  77.  Yields  oxygen 
in  passing  through  the  capillaries,  26,  79.  Con- 
tains carbonic  acid  dissolved  or  combined  with 
soda,  79. 

Asparagine.  Its  composition,  101.  Its  relation  to 
taurine  and  bile,  56.  Theory  of  its  action  on 
the  bile,  57. 

Assimilation.  In  animals  it  is  independent  of  ex- 
ternal influences,  11.  Depends  on  the  presence 
in  the  blood  of  compounds  of  proteine,  such  as 
fibrine,  albumen,  or  caseine,  21.  Is  more  ener- 
getic in  the  young  than  in  the  adult  animal,  27. 
Is  also  more  energetic  in  the  herbivora  than  in 
the  carnivora,  31. 

Atmosphere.     See  Air. 

Azotized  Products.  Of  vegetable  life,  55 — 57. 
Of  the  metamorphosis  of  tissues.  Necessary 
for  the  formation  of  bile  in  the  herbivora,  51. 
In  man,  53.  May  be  replaced  by  azotized  ve- 
getable compounds,  54.  Theory  of  this,  56 — 
57.  Of  the  transformation  of  the  bile,  or  of 
choleic  acid;  how  related  to  the  constituents  of 
urine,  50. 

B. 

Beans.     Composition  of,  83. 

Beer.  Forms  part  of  the  diet  of  soldiers  in  Ger 
many,  83,  85. 


INDEX. 


105 


Bees.  Their  power  of  forming  wax  from  honey, 
90—92. 

Benzoic  Acid.     See  Acid,  Benioic. 

Berthollet.     His  analysis  of  oxalic  acid,  99. 

Berzelius.  His  analysis  of  potato  starch,  88 ;  of 
sugar  of  milk,  89 ;  of  gum,  89 ;  of  cane  sugar,  90. 

Bezoar  stones.     See  Acid,  Lithofellic. 

Blanchet.     His  analysis  of  solanine,  100. 

Bile.  In  the  carnivora  is  a  product  of  the  meta- 
morphosis of  the  tissues,  along  with  urate  of 
ammonia,  44.  May  be  represented  by  choleate 
of  soda,  with  which,  however,  it  is  not  identi- 
cal, 97.  Products  of  its  transformation,  44, 
97.  Remarks  on  these,  96 — 97.  Origin  of 
bile,  26,  46.  Starch,  &c.,  contribute  to  its 
formation  in  the  herbivora,  47,  48,  51,  53. 
Soda  essential  to  it,  49,  52.  Relation  of  bile 
to  urine,  50,  To  starch,  51.  To  fibrine,  44. 
To  caffeine,  &c.,  asparagine,  and  theobromine, 
57.  For  the  acid  substances  derived  from  bile, 
choleic,  choloidic,  and  cholic  acids,  see  Acid, 
Choleic,  &c.  Yields  taurine,  44.  Contains 
cholesterine,  32,  97.  Also  stearic  and  mar- 
garic  acids,  97.  Its  function:  to  support 
respiration  and  produce  animal  heat  by  pre- 
senting carbon  and  hydrogen  in  a  very  soluble 
form  to  the  oxygen  of  the  arterial  blood,  26,  27. 
Amount  secreted  by  the  dog,  the  horse,  and 
man,  27.  It  returns  entirely  into  the  circula- 
tion, and  disappears  completely,  26,  27. 

Blood.  The  fluid  from  which  every  part  of  the 
body  is  formed,  13.  Its  chief  constituents,  21. 
How  formed  from  vegetable  food,  22.  Can 
only  be  formed  from  compounds  of  proteine,  23. 
Is  therefore  entirely  derived  from  vegetable  pro- 
ducts in  the  herbivora,  and  indirectly  also  by 
the  carnivora,  which  feed  on  the  flesh  of  the 
former,  23.  Its  composition  identical  with  that 
of  flesh,  44.  Analysis  of  both,  96.  The  se- 
cretions contain  all  the  elements  of  the  blood, 
43.  Its  relation  to  bile  and  urine,  44.  Pro- 
ducts of  the  oxidation  of  blood,  45.  Excess  of 
azotized  food  produces  fulness  of  blood  and  dis- 
ease, 47.  Soda  is  present  in  the  blood,  52. 
Important  properties  of  the  blood,  54—55. 
Venous  blood  contains  iron,  probably  as  pro- 
toxide ;  arterial  blood,  probably  as  peroxide,  79. 
Theory  of  the  poisonous  action  of  sulphuretted 
hydrogen  and  prussic  acid:  they  decompose 
the  compound  of  iron  in  the  blood,  79.  The 
blood,  in  analogous  morbid  states,  ought  to  be 
chemically  examined,  80. 

Blood-letting.  Theory  of  its  mode  of  action,  78. 
It  may  produce  opposite  effects  in  different 
cases,  77. 

Boeckmann.  His  analysis  of  black  bread,  83 ;  of 
potatoes,  83;  of  dry  beef,  96;  of  dry  blood,  96; 
of  roasted  flesh,  100. 

Bones.  Phosphoric  acid  of  the  food  regained  to 
assist  in  forming  them,  31.  Gelatine  of  bones 
digested  by  dogs,  35.  See,  further,  Gelatine. 
Cause  of  brittleness  in  bones,  36. 

Boussingault.  His  analysis  of  potatoes,  83.  His 
comparison  of  the  food  and  excretions  in  the 
horse  and  cow,  Table,  86.  His  analysis  of 
gluten,  87;  of  vegetable  albumen,  87;  of  ve- 
getable caseine,  88;  of  oats,  89;  of  hay,  89. 

Braconnot.  On  the  presence  of  lactic  acid  in 
gastric  juice,  38 ;  of  iron  in  the  gastric  juice  of 
the  dog,  38. 

Brain.  See  Acid,  Cerebric,  and  Nervous  Matter. 
14 


Bread.     Analysis  of,  83. 

Brund.     His  analysis  of  sugar  of  milk,  89. 

Buckwheat.     Analysis  of  starch  from,  88. 

Burdach.  His  statement  of  the  amount  of  bila 
secreted  by  animals,  27. 

Butter.  Forms  a  part  of  the  food  of  soldiers  in 
Germany,  83,  84. 

Buzzard.  Its  excrements  consist  of  urate  of  am- 
monia, 24. 

C. 

Caffeine.  Identical  with  theine,  56.  Its  relation 
to  taurine  and  bile,  56.  Theory  of  its  mode  of 
action,  57.  Its  composition,  101. 

Cane  Sugar.     Its  composition,  90. 

Carbon.  Is  accumulated  in  the  bile,  21.  Is  given 
off  as  carbonic  acid,  14.  Excess  of  carbon 
causes  hepatic  diseases,  17.  By  combining 
with  oxygen,  it  yields  the  greater  part  of  the 
animal  heat.  See  Animal  Heat,  Bile,  and  Acid, 
Carbonic.  Amount  of  carbon  oxidized  daily  in 
the  body  of  a  man,  14.  Calculations  on  which 
this  statement  is  founded,  82 — 85.  Amount 
consumed  by  the  horse  and  cow,  14.  Different 
proportions  of  carbon  in  different  kinds  of  food, 
15.  Carbon  of  flesh  compared  with  that  of 
starch,  showing  the  advantage  of  a  mixed  diet, 
30.  Calculation  on  which  this  statement  is 
founded,  89.  Amount  of,  carbon  in  dry  blood 
calculated,  82.  Amount  in  the  food  of  prisoners 
calculated,  87. 

Carbonic  Acid.     See  Acid,  Carbonic. 

Carbonates.     They  occur  in  the  blood,  21. 

Calculus,  Mulberry.  Derived  from  the  imperfed 
oxidation  of  uric  acid,  45.  Uric  acid  calculus 
is  formed  in-  consequence  of  deficiency  of  in- 
spired oxygen,  or  excess  of  carbon  in  the  food, 
45.  See  Acid,  Uric.  Bezoar  stones  composed 
of  lithofellic  acid,  49. 

Carnivora.  Their  nutrition  the  most  simple,  22. 
It  is  ultimately  derived  from  vegetables,  23. 
Their  young,  like  graminivora,  require  non- 
azotized  compounds  in  their  food,  23.  Their 
bile  is  formed  from  the  metamorphosis  of  their 
tissues,  25,  26.  The  process  of  assimilation  in 
adult  and  young  carnivora  compared,  27.  Their 
urine,  30.  The  assimilative  process  in  adult 
carnivora  less  energetic  than  in  graminivora,  31. 
They  are  destitute  of  fat,  31.  They  swallow 
less  air  with  their  food  than  graminivora,  40. 
Concretions  of  uric  acid  are  never  found  in 
them,  47.  Both  soda  and  ammonia  found  in 
their  urine,  52. 

Caseine.  One  of  the  azotized  nutritious  products 
of  vegetable  life,  22.  Abundant  in  leguminous 
plants,  22.  Identical  in  organic  composition 
with  fibrine  and  albumen,  22,  23.  Animal 
caseine  found  in  milk  and  cheese;  identical 
with  vegetable  caseine,  23.  Furnishes  blood 
to  the  young  animal,  24.  Is-  one  of  the  plastic 
elements  of  nutrition,  35.  Yields  proteine,  37. 
Its  relation  to  proteine,  42.  It  contains  sul- 
phur, 42.  Potash  essential  to  its  production,  52. 
Contains  more  of  the  earth  of  bones  than  blood 
does,  24.  Its  analysis,  88. 

Cerebric  Acid.     See  Acid,  Cerebric. 

Change  of  Matter.  See  Metamorphosis  of  Tisbuea. 

Chemical  Attraction.     See  Affinity. 

Chevreul.  His  researches  on  fat,  32.  His  ana 
lysis  of  fat,  90 ;  of  cholesterine,  90. 

Chloride  of  Sodium.     See  Common  Salt 

Choleic  Acid.    See  Acid,  Choleic. 


106 


INDEX. 


Cholesterine.     See  Bile. 

Cholic  Acid.     See  Acid,  Cholic. 

Choloidic  Acid.     See  Acid,  Choloidic. 

Chondrine.  Its  relation  to  proteine,  42.  Ana- 
lysis of  tissues  containing  it,  95. 

Chronic  Diseases.  The  action  of  inspired  oxy- 
gen is  the  cause  of  death  in  them,  17,  18. 

Chyle.,  When  it  has  reached  the  thoracic  duct, 
it  is  alkaline,  and  contains  albumen  coagulable 
by  heat,  47. 

Chyme.  It  is  formed  independently  of  the  vital 
force,  by  a  chemical  transformation,  37.  The 
substance  which  causes  this  transformation  is 
derived  from  the  living  membrane  of  the  sto- 
mach, 37.  Chyme  is  acid,  47. 

Clothing.  Warm  clothing  is  a  substitute  for  food 
to  a  certain  extent,  16.  Want  of  clothing  ac- 
celerates the  rate  of  cooling,  and  the  respira- 
tions, and  thus  increases  the  appetite,  16. 

Cold.  Increases  the  appetite  by  accelerating  the 
respiration,  16.  Is  most  judiciously  employed 
as  a  remedy  in  cerebral  inflammation,  76. 

Concretions.  See  Calculus,  and  Acid,  Uric;  also 
Acid,  Lithofellic. 

Constituents,  Azotized.  Of  blood:  see  Fibrine 
and  Albumen.  Of  vegetables:  See  Fibrine, 
Vegetable;  Albumen,  Vegetable;  Caseine,  Ve- 
getable; Alkalies,  Vegetable;  and  Caffeine. 
Of  bile:  see  Acid,  Choleic,  Cholic,  and  Cho- 
loidic. Of  urine:  see  Acid,  Uric;  Urea,  and 
Allantoine. 

Cooling.     See  Cold  and  Clothing. 

Couerbe.     His  analysis  of  cholesterine,  90. 

Cow.  Amount  of  carbon  expired  by  the,  14. 
Comparison  of  the  food  with  the  excretions  of 
the  cow,  86. 

Crum.     His  analysis  of  cane  sugar,  90. 

Cultivation.     Is  the  economy  of  force,  30. 

Cyamelide.     Its  formula,  81. 

Cyanic  Acid.     See  Acid,  Cyanic. 

Cyanide  of  Iron.     Its  remarkable  properties,  78. 

Cyanuric  Acid.     See  Acid,  Cyanuric. 
D. 

Davy.     Oxygen  consumed  by  an  adult  man,  82. 

Death.  Cause  of,  in  chronic  diseases,  17,  18. 
Caused  in  old  people  by  a  slight  depression  of 
temperature,  75.  Definition  of  it,  74. 

Demargay.  His  analysis  of  choleic  acid,  choloidic 
acid,  and  taurine,  96.  Remarks  on  his  Re- 
searches on  Bile,  97. 

Denis.  His  experiments  on  the  conversion  of 
fibrine  into  albumen,  21. 

Despretz.  His  calculation  of  the  heat  developed 
in  the  combustion  of  carbon,  19. 

Diabetes  Mellitus.  The  sugar  found  in  the  urine 
in  this  disease  is  grape  sugar,  and  is  derived 
from  the  starch  of  the  food,  35. 

Diastase.  Analogy  between  its  solvent  action  on 
starch,  and  that  of  the  gastric  juice  on  coagu- 
lated albumen,  38. 

Diffusion  of  Gases.  Explains  the  fact  that  nitro- 
gen is  given  out  through  the  skin  of  animals, 
40;  and  the  poisonous  action  of  feather-white 
wine,  39. 

Digestion.  Is  effected  without  the  aid  of  the  vital 
force,  by  a  metamorphosis  derived  from  the 
transformation  of  a  substance  proceeding  from 
the  lining  membrane  of  the  stomach,  37.  The 
oxygen  introduced  with  the  saliva  assists  in 
the  process,  38,  Lactic  acid  has  no  share  in 
it,  38. 


Disease.  Theory  of,  74  et  seq.  Cause  of  deato 
in  chronic  disease,  17.  Disease  of  liver  caused 
by  excess  of  carbon  or  deficiency  of  oxvgen,  16 
Prevails  in  hot  weather,  17. 

Dog.  Amount  of  bile  secreted  by,  27.  Digests 
the  gelatine  of  bones,  35.  His  excrements  con- 
tain only  bone  earth,  36.  Concretion  of  urate 
of  ammonia  said  to  have  been  found  by  Las- 
saigne  in  a  dog,  doubtful,  47  (note.') 

Dumas.     His   analysis  of  choleic  acid,  96;   of 
choloidic  acid,  96;  of  taurine,  ib.\  of  cholic 
acid,  97;  of  hippuric  acid,  98. 
E. 

Eggs.  Albumen  of  the  white  and  of  the  yolk 
identical,  37  Analysis  of  both,  93;  of  lining 
membrane,  95.  The  fat  of  the  yolk  may  con- 
tribute to  the  formation  of  nervous  matter,  37. 
This  fat  contains  iron,  37. 

Elaldehyde.     See  Aldehyde. 

Elements.     Of  nutrition,  35.     Of  respiration,  35 

Empyreumatics.  They  check  transformations,  54. 
Their  action  on  ulcers,  41. 

Equilibrium.  Between  waste  and  supply  of  mat- 
ter is  the  abstract  state  of  health,  74,  78. 
Transformations  occur  in  compounds  in  which 
the  chemical  forces  are  in  unstable  equili- 
brium, 37. 

Ettling.  His  analysis  of  wax,  92.  Ettling  and 
Will,  their  analysis  of  lithofellic  acid,  100. 

Excrements.  Contain  little  or  no  bile  in  man 
and  in  the  herbivora,  none  at  all  in  the  dog  and 
other  carnivora,  27.  Those  of  the  dog  are 
phosphate  of  lime,  35.  Those  of  serpents  are 
urate  of  ammonia,  24.  Those  of  birds  also 
contain  that  salt,  24.  Those  of  the  horse  and 
cow  compared  with  their  food,  86. 

Excretions.     Contain,  with  the   secretions,  the 
elements  of  the  blood  or  of  the  tissues,  43,  44. 
Those  of  the  horse  and  cow  compared  with 
their  food,  86.     Bile  is  not  an  excretion,  26. 
F. 

Fseees.     Analysis  of,  83. 

Fat  Theory  of  its  production  from  starch,  when 
oxygen  is  deficient,  32  et  seq.  /  from  other  sub- 
stances, 32.  The  formation  of  fat  supplies  a 
new  source  of  oxygen,  33 ;  and  produces  heat, 
33  et  seq.  Maximum  of  fat,  how  obtained,  34. 
Carnivora  have  no  fat,  31.  Fat  in  stall-fed 
animals,  33.  Occurs  in  some  diseases  in  the 
blood,  35.  Fat  in  the  women  of  the  East,  36. 
Composition  compared  with  that  of  sugar,  32. 
Analysis  of  fat,  90.  Disappears  in  starvation, 
17.  Is  an  element  of  respiration,  35. 

Fattening  of  Animals.     See  Fat. 

Featherwhite  Wine.     Its  poisonous  action,  39. 

Febrile  Paroxyism.     Definition  of,  75. 

Fehling.  His  analysis  of  metaldehvde  and  elal- 
dehyde,  92. 

Fermentation.  May  be  produced  by  any  azotized 
matter  in  a  state  of  decomposition,  40.  Is  ar- 
rested by  empyreumatics,  40.  Is  analogous  to 
digestion,  40. 

Fever.     Theory  and  definition  of,  75. 

Fibre.     Muscular.     See  Flesh. 

Fibrine.  Is  an  element  of  nutrition,  35.  Animal 
and  vegetable  fibrine  are  identical,  22.  Is  a 
compound  of  proteine,  36.  Its  relation  to  pro- 
teine, 42.  Convertible  into  albumen,  21.  Is 
derived  from  albumen  during  incubation,  37. 
Its  analysis,  87,  94,  Vegetable  fibrine,  how 
obtained.  22, 


INDEX. 


in? 


Fishes.  Yield  phosphuretted  hydrogen,  59  (note.] 

Flesh.  Consists  chiefly  of  fibrine,  but,  from  the 
mixture  of  fat  and  membrane,  has  the  same 
formula  as  blood,  44.  Analysis  of  flesh,  96,  100. 
Amount  of  carbon  in  flesh  compared  with  that 
of  starch,  30,  86. 

Food.  Must  contain  both  elements  of  nutrition 
and  elements  of  respiration,  35.  Nutritious 
food,  strictly  speaking,  is  that  alone  which  is 
capable  of  forming  blood,  21.  Whether  derived 
from  animals  or  from  vegetables,  nutritious  food 
contains  proteine,  22,  37  et  seq.  Changes 
which  the  food  undergoes  in  the  organism  of 
the  carnivora,  24  et  seq.  The  food  of  the  herbi- 
vora always  contains  starch,  sugar,  &c.,  28. 
Food,  how  dissolved,  38  et  seq.  Azotized  food 
has  no  direct  influence  on  the  formation  of 
uric  acid  calculus,  45.  Effects  of  superabundant 
azotized  food.  47.  Non-azotised  food  contri- 
butes to  the  formation  of  bile,  and  thus  to 
respiration,  47  et  seq.  Salt  must  be  added  to 
the  food  of  herbivora,  in  order  to  yield  soda  for 
the  bile,  52.  Caffeine,  &c.,  serve  as  food  for 
the  liver,  59.  The  vegetable  alkalies  may  be 
viewed  as  food  for  the  organs  which  form  the 
nervous  matter,  59.  Amount  of  food  con- 
sumed by  soldiers  in  Germany,  83.  Its  ana- 
lysis, 82.  Food  of  the  horse  and  cow  com- 
pared with  their  excretions,  86. 

Formulae.  Explanation  of  their  use,  81.  How 
reduced  to  100  parts,  81.  Formulae  of  albu- 
men, ftbrine,  caseine,  and  animal  tissues,  42. 
Formula  of  proteine,  41 ;  of  blood  and  flesh,  44 ; 
of  fat,  32;  of  cholesterine,  32;  of  aldehyde, 
acetic  acid,  oil  of  bitter  almonds,  and  benzoic 
acid,  81 ;  of  cyamelide,  cyanic  acid,  and  cyan- 
uric  acid,  8 1  ;  of  choleic  acid,  44 ;  of  choloidic 
acid  and  cholic  acid,  44;  of  gelatine,  46;  of 
hippuric  acid,  48 ;  of  lithofellic  acid,  49 ;  of 
taurine,  49  ;  of  alloxan,  49.  See  Analysis. 

Francis.     His  analysis  of  picrotoxine,  100. 

Fremy,  Lameyran  and  Fremy.  Their  analysis  of 
gas  from  the  abdomen  of  cows  after  excess  in  fresh 
food,  93.  His  researches  on  the  brain,  21,  57. 

Frequency  of  the  pulse  and  respiration  in  different 
animals,  15,  87. 

Fruits.     Contain  very  little  carbon,  and  hence  are 
adapted  for  food  in  hot  climates,  15. 
G. 

Gas.  Analysis  of  gas  from  abdomen  of  cows 
after  excess  in  fresh  food,  39,  93.  Analysis  of 
gas  from  the  stomach  and  intestines  of  executed 
criminals,  39,  93. 

Gastric  Juice.  Contains  no  solvent  but  a  sub- 
stance in  a  state  of  metamorphosis,  by  the  pre- 
sence of  which  the  food  is  dissolved,  37.  Con- 
tains free  acid,  37.  Contains  no  lactic  acid,  38. 
In  the  dog  has  been  found  to  contain  iron,  38. 
See  Digestion,  Chyme,  Food. 

Gay-Lussac  and  Thenard.  Their  analysis  of 
starch,  88  ;  of  sugar  of  milk,  and  of  gum,  89  ;  of 
cane  sugar,  90  ;  of  wax,  92  ;  of  oxalic  acid,  99. 

Gelatine.  Is  derived  from  proteine,  but  is  no 
longer  a  compound  of  proteine,  and  cannot 
form  blood,  42  et  seq.  May  serve  as  food  for 
the  gelatinous  tissues,  and  thus  spare  the  sto- 
mach of  convalescents,  35,  43.  In  starvation 
the  gelatinous  tissues  remain  intact,  35.  Its 
relation  to  proteine,  42.  Its  formula,  46.  Its 
analysis,  94,  100. 

'.ToebeL     His  analysis  of  gum,  89. 


Globules  of  the  blood  are  the  carriers  of  oxygen 
to  all  parts  of  the  body,  54 — 55.  They  con- 
tain iron,  77  et  seq. 

Gluten.  Contains  vegetable  fibrine,  22.  Ana- 
lysis of  it,  87. 

Gmelin.     On  the  sugar  of  bile,  47. 

Goose.     How  fattened  to  the  utmost,  34, 

Graminivora.     See  Herbivora. 

Grape-sugar.  An  element  of  respiration,  35.  Is 
identical  with  starch  sugar  and  diabetic  sugar, 
29.  Its  composition,  29.  Its  analysis,  88. 

Growth,  or  increase  of  mass,  greater  in  gramini- 
vora  than  in  carnivora,  31.  Depends  on  the 
blood,  21 ;  and  on  compounds'  of  proteine,  37, 
See  Nutrition. 

Gum.  An  element  of  respiration,  36.  Its  com- 
position, 35.  Is  related  to  sugar  of  milk,  35. 
Its  analysis,  89. 

Gundlach.     His  researches  on  the  formation  of 
of  wax  from  honey  of  the  bee,  91. 
H. 

Hair.  Analysis  of,  95.  Its  relation  to  proteine, 
42.  Analysis  of  proteine  from  hair,  93. 

Hay.     Analysis  of,  89. 

Hepatic  Diseases.     Cause  of,  16. 

Herbivora.  Their  blood  derived  from  compounds 
of  proteine  in  their  food,  23.  But  they  require 
also  for  their  support  non-azotized  substances, 
28.  These  last  assist  in  the  formation  of  their 
bile,  47  et  seq.  They  retain  the  phosphoric 
acid  of  their  food  to  form  bone  and  nervous 
matter,  31.  Their  urine  contains  very  little 
phosphoric  acid,  31.  The  energy  of  vegetative 
life  in  them  is  very  great,  31.  They  become 
fat  when  stall-fed,  31. 

Hess.     His  analysis  of  wax,  93. 

Hybernating  Animals.  Their  fat  disappears  dur- 
ing the  winter  sleep,  17.  They  secrete  bile 
and  urine  during  the  same  period,  26. 

Hippuric  Acid.     See  Acid,  Hippuric. 

Horn.  Analysis  of,  95.  Contains  proteine ;  its 
relation  to  proteine,  42.  Analysis  of  proteine 
from  horn,  93. 

Horse.  Amount  of  carbon  expired  by,  14.  Com- 
parison of  his  food  with  his  excretions,  86 
Force  exerted  by  a  horse  in  mechanical  motior 
compared  to  that  exerted  by  a  whale,  70. 

Hydrocyanic  Acid.     See  Acid,  Hydrocyanic. 

Hydrogen.  By  combining  with  oxygen  contri 
butes  to  produce  the  animal  heat,  17. 

Ice.  Is  judiciously  employed  as  a  remedy  in 
cerebral  inflammation,  76. 

Inorganic  constituents  of  albumen,  fibrine,  anJ 
caseine,  21,  41,  42. 

Jobst.     His  analysis  of  theine,  101. 

Jones,  Dr.  Bence.  His  analysis  of  vegetable 
fibrine,  86 ;  of  vegetable  albumen,  87 ;  of  ve- 
getable caseine,  87;  of  gluten,  87;  of  the  albu 
men  of  yolk  of  egg,  93,  94;  of  the  albumen  of 
brain,  94. 

Iron.  Is  an  essential  constituent  of  the  globules 
of  the  blood,  77  et  seq.  Is  found  in  the  fat  of 
yolk  of  egg,  37.  Also  in  the  gastric  juice  of 
the  dog,  38.  Singular  properties  of  its  com- 
pounds, 78. 

Isomeric  Bodies,  36,  81. 
K. 

Keller.  His  researches  on  the  conversion  of 
benzoic  acid  into  hippuric  acid  in  the  human 
body,  101. 


108 


INDEX. 


Kidneys.  They  separate  from  the  arterial  blood 
the  nitrogenized  compounds  destined  for  excre- 
tion, 49. 

L. 

Lactic  Acid.     See  Acid,  Lactic. 

Lavoisier.  His  calculation  of  the  amount  of  in- 
spired oxygen,  14,  81. 

Lehmann.  On  the  presence  of  lactic  acid  in 
gastric  juice,  38. 

Liebig.  His  analysis  of  sugar  of  milk,  89;  of 
cane  sugar,  90 ;  of  aldehyde,  92 ;  of  uric  acid, 
97;  of  hippuric  acid,  98 ;  of  quinine,  100;  of 
morphia,  101;  of  asparagine,  101.  His  calcu- 
lation of  the  carbon  daily  expired  as  carbonic 
acid,  14,  82.  Table,  84.  His  remarks  on 
Demargay's  researches  on  bile,  96,  97. 

Liebig  and  Pfaff.     Their  analysis  of  caffeine,  101. 

Liebig  and  Wohler.  Their  analysis  of  alloxan, 
98 ;  of  urea,  98 ;  of  allantoine,  98 ;  of  xanthic 
oxide,  99  ;  of  oxaluric  acid,  99 ;  of  parabanic 
acid,  99. 

Lentils.  Contain  vegetable  caseine,  22.  Ana- 
lysis of,  82,  83.  Form  part  of  the  diet  of  sol- 
diers in  Germany,  83.  Table,  85. 

Light.  Its  influence  on  vegetable  life  analogous 
to  that  of  heat  on  animal  life,  69. 

Lime.     Phosphate  of.     See  Bones. 

Liver.     It  separates  from   the  venous  blood  the 

carbonized  constituents  destined  for  respiration, 

25.     Diseases  of  the  liver,  how  produced,  1 6. 

Accumulation  of  fat  in  the  liver  of  the  goose,  35. 

M. 

Maize.     Analysis  of  starch  from,  88. 

Marchand.  On  the  amount  of  urea  in  the  urine 
of  the  dog  when  fed  on  sugar,  26.  His  ana- 
lysis of  cholesterine,  90. 

Marcet.     His  analysis  of  gluten,  87. 

Martius.     His  analysis  of  guaranine,  101 

Mechanical  Effects.     See  Motion. 

Medicine.  Definition  of  the  objects  of,  75  et  seq, 
Action  of  medicinal  agents,  54  et  seq. 

Menzies.  His  calculation  of  the  amount  of  in- 
spired oxygen,  14,  81. 

Metaldehyde.     See  Aldehyde. 

Metamorphosis  of  Tissues,  36  et  seq.  In  other 
parts  of  the  volume,  passim. 

Milk.  Is  the  only  natural  product  perfectly  fitted 
to  sustain  life,  23.  Contains  caseine,  23.  Fat 
(butter),  23.  Sugar  of  milk,  23.  Earth  of 
bones,  23.  And  potash,  52. 

Morphia.  Contains  less  nitrogen  than  quinine, 
56.  Its  analysis,  101. 

Mitscherlich.  His  analysis  of  uric  acid,  96 ;  of 
hippuric  acid,  96. 

Momentum.     Offeree,  61.     Of  motion,  61. 

Motion.  Phenomena  of  motion  in  the  animal 
body,  60  et  seq.  Different  sources  of  motion, 
60.  Momentum  of  motion,  61.  Motion  pro- 
pagated by  nerves,  60.  Voluntary  and  invo- 
luntary motions  accompanied  by  a  change  of 
form  and  structure  in  living  parts,  66.  Motion 
derived  from  change  of  matter,  66  et  seq.  The 
cause  of  motion  in  the  animal  body  is  a  peculiar 
force,  69.  The  sum  of  the  effects  of  motion  in 
the  body  proportional  to  the  amount  of  nitrogen 
in  the  urine,  72. 

Mulberry  Calculus.     See  Calculus. 

Mulder.  Discovered  proteine,  36.  His  analysis 
of  fibrine  of  blood,  87.  Of  animal  caseine,  88. 
Of  proteine,  88.  Of  fibrine,  94  Of  gelatine, 
94,  Of  chondrine,  95. 


Muscle.     See  Flesh. 

Muscular  Fibre.  Its  transformation  depends  on 
the  amount  of  force  expended  in  producing 
motion,  66. 

N. 

Nerves.  Are  the  conductors  of  the  vital  force, 
and  of  mechanical  effects,  66.  Effects  of  the 
disturbance  of  their  conduting  power,  68.  They 
are  not  the  source  of  animal  heat,  18. 

Nervous  Life.    Distinguished  from  vegetative,  20. 

Nervous  Matter.  Contains  albumen,  and  fatty 
matter  of  a  peculiar  kind,  21.  Vegetables  can- 
not produce  it,  23.  The  fat  of  yolk  of  egg 
probably  contributes  to  its  formation,  37.  The 
phosphoric  acid  and  phosphates,  formed  in  the 
metamorphosis  of  the  tissues  of  the  herbivora, 
are  retained  to  assist  in  the  formation  of  nervous 
matter,  31.  The  vegetable  alkalies  affect  the 
nervous  system,  57.  Composition  of  cerebric 
acid.  Theory  of  the  action  of  the  vegetable 
alkalies,  58. 

Nitrogen.  Essential  to  all  organized  structures, 
21.  Substances  in  the  body  which  are  destitute 
of  it  not  organized,  21.  Abounds  in  nutritious 
vegetables,  22,  Nutritious  forms  in  which  it 
occurs,  22  et  seq.  Occurs  in  all  vegetable  poi- 
sons, 56 ;  also  in  a  few  substances  which  are 
neither  nutritious  nor  poisonous,  but  have  a 
peculiar  effect  on  the  system,  such  as  caffeine* 
56  et  seq. 

Nitrogenized.     See  Azotized. 

Non-Azotized.  Constituents  of  food.  See  Starch. 

Nutrition.  Depends  on  the  blood,  21.  On  Albu- 
men, fibrine,  or  caseine,  21  et  seq.  Elements 
of  nutrition,  35.  Compounds  of  proteine  alonb 
are  nutritious,  37.  Occurs  when  the  vital  force 
is  more  powerful  than  the  opposing  chemical 
forces,  60.  Theory  of  it,  63.  Is  almost  unli- 
mited in  plants  from  the  absence  of  nerves,  64. 
Depends  on  the  momentum  of  force  in  each 
part,  68.  Depends  also  on  heat,  72. 
O. 

Oats.  Amount  required  to  keep  a  horse  in  good 
condition,  29.  Analysis  of,  89. 

Oil  of  Bitter  Almonds.  Its  composition.  How 
related  to  benzoic  acid,  81. 

Old  Age.     Characteristics  of,  73  et  seq. 

Oppermann.     His  analysis  of  wax,  92. 

Organs.  The  food  of  animals  always  consist  of 
parts  of  organs,  11.  All  organs  in  the  body 
contain  nitrogen,  21.  There  must  exist  organs 
for  the  production  of  nervous  matter,  59 ;  and 
the  vegetable  alkalies  may  be  viewed  as  food 
for  these  organs,  59. 

Organized  Tissues.  All  contain  nitrogen,  21. 
All  such  as  are  destined  for  effecting  the  change 
of  matter  are  full  of  small  vessels,  67.  Their 
composition,  42.  The  gelatinous  and  cellular 
tissues,  and  the  uterus,  not  being  destined  for 
that  purpose,  are  differently  constructed,  67. 
Waste  of  organized  tissues  rapid  in  carnivora, 
30. 

Origin.  Of  animal  heat,  15,  18.  Of  fat,  31  el 
seq.  Of  the  nitrogen  exhaled  from  the  lungs, 
39  et  seq.  Of  gelatine,  42  et  seq.,  48.  Of 
uric  acid  and  urea,  44  et  seq.  Of  bile,  44,  47, 
48  et  seq.  Of  hippuric  acid,  48,  101.  Of  the 
chief  secretions  and  excretions,  49.  Of  the 
soda  of  the  bile,  52  et  seq.  Of  the  nitrogen  in 
bile,  53.  Of  nervous  matter,  57  et  **q» 

Ortigosa.   His  analysis  of  starch,  88 


INDEX 


1(19 


Oxalic  Acid.  A  product,  along  with  urea,  of  the 
partial  oxidation  of  uric  acid,  occurring  in 
the  form  of  mulberry  calculus,  45.  Its  analysis, 
99. 

Oxygen.  Amount  consumed  by  man  daily,  14, 
80.  Amount  consumed  daily  in  oxidizing  car- 
bon by  the  horse  and  cow,  14.  The  absorption 
of  oxygen  characterizes  animal  life,  11.  The 
action  of  oxygen  is  the  cause  of  death  in  star- 
vation and  in  chronic  diseases,  17 — 18.  The 
amount  of  oxygen  inspired  varies  with  the  tem- 
perature, dry  ness,  and  density  of  the  air,  15. 
Is  carried  by  arterial  blood  to  all  parts  of  the 
body,  54.  Fat  differs  from  sugar  and  starch 
only  in  the  amount  of  oxygen,  32.  It  also 
contains  less  oxygen  than  albumen,  fibrine,  &c., 
32.  The  formation  of  fat  depends  on  a  defi- 
ciency of  oxygen,  33  et  seq.  /  and  helps  to  sup- 
ply this  deficiency,  33.  Oxygen  essential  to 
digestion,  38.  Relation  of  oxygen  to  some  of 
the  tissues  formed  from  proteine,  42.  Oxygen 
and  water,  added  to  blood  or  to  flesh,  yield  the 
elements  of  bile  and  of  urine,  44.  Action  of 
oxygen  on  uric  acid,  44,  45  :  on  hippuric  acid, 
31,45;  on  blood,  45 ;  on  proteine,  with  uric 
acid,  48  ;  on  proteine  and  starch,  with  water,  49  ; 
on  choleic  acid,  49 ;  on  proteine,  with  water, 
49.  By  depriving  starch  of  oxygen  and  water, 
choloidic  acid  may  be  formed,  51.  Oxygen 
is  essential  to  the  change  of  matter.  55.  Its 
action  on  the  azotized  constituents  of  plants 
when  separated,  64.  Its  action  on  the  muscular 
fibre  essential  to  the  production  of  force,  66,  67. 
Oxygen  is  absorbed  by  hybernating  animals,  71. 
Is  the  cause  of  the  waste  of  matter,  72 ;  and 
of  animal  heat,  72,  74.  Blood-letting  acts  by 
diminishing  the  amount  of  oxygen  which  acts 
on  the  body,  75.  Its  absorption  is  the  cause  of 
the  change  of  colour  from  venous  to  arterial 
blood,  77.  The  globules  probably  contain  oxide 
of  iron,  protoxide  in  venous  blood,  peroxide  in 
arterial,  78  et  seq.  All  parts  of  the  arterial 
blood  contain  oxygen,  55,  77,  79. 
P. 

Pears.     Analysis  of  starch  from  unripe,  88. 

Peas.  Form  part  of  the  diet  of  soldiers  in  Ger- 
many, 83,  85.  Abound  in  vegetable  caseine, 
22.  Analysis  of  peas,  83  ;  of  starch  from 
peas,  88. 

Pepys  and  Allen.  Their  calculation  of  the 
amount  of  inspired  oxygen,  82. 

Peroxide  of  Iron.  Probably  exists  in  arterial 
blood,  78  et  seq. 

Pfluger.  His  analysis  of  the  gas  obtained  by 
puncture  from  the  abdomen  of  cattle  after  ex- 
cess in  green  food,  93. 

Phenomena  of  motion  in  the  animal  body,  60 
et  seq. 

Phosphates.    See  Bones. 

Phosphoric  Acid.   See  Acid,  Phosphorc. 

Phosphorus.  Exists  in  albumen  and  hbrine,  21, 
23,42.  It  is  not  known  in  what  form,  41  et 
seq.  Is  an  essential  constituent  of  nervous  mat- 
ter, 57, 59. 

Phosphuretted  Hydrogen.  Occurs  among  the  pro- 
ducts of  the  putrefaction  of  fishes,  59. 

Picrotoxine.  Contains  nitrogen,  56  (note.')  Its 
analysis,  100. 

Plants.  Distinguished  from  animals  by  fixing 
carbon  and  giving  out  oxygen,  11,  64;  by  the 
want  of  nerves  and  of  locomotive  powers,  11. 


Their  capacity  of  growth  almost  unlimited,  64, 
Cause  of  death  in  plants,  64. 

Playfair,  Dr.  L.  His  formula  for  blood,  38.  Hia 
analysis  of  faeces,  of  peas,  of  lentils,  of  beans, 
82 ;  of  flesh  and  of  blood,  96 ;  of  roasted  flesh, 
100. 

Poisons,  Vegetable.  Always  contain  nitrogen, 
55  et  seq.  Different  kinds  of  poisons,  54. 
Theory  of  the  action  of  prussic  acid  and  sul- 
phuretted hydrogen,  80. 

Polymeric  Bodies,  36. 

Potash.  Essential  to  the  production  of  caseine  01 
milk,  52. 

Potatoes.  Amount  of  carbon  in,  83.  They. form 
part  of  the  diet  of  soldiers  in  Germany,  83. 
Analysis  of,  83  ;  of  starch  from,  83  ;  of  sola- 
nine  from  the  buds  of  germinating  potatoes,  100. 

Prevost  and  Dumas.  On  the  frequency  of  the 
pulse  and  respirations,  86. 

Products.  Of  the  metamorphosis  of  tissues  found 
in  the  bile  and  urine,  43.  Of  the  action  of 
muriatic  acid  on  bile,  44.  Of  the  action  of 
potash  on  bile,  44.  Of  the  action  of  water  and 
oxygen  on  blood  or  fibre,  44.  Of  the  oxidation 
of  uric  acid,  45.  Of  the  oxidation  of  blood,  45 
Of  the  action  of  water  on  proteine,  46.  Of  the 
action  of  urea  on  lactic  and  benzoic  acids,  48 
Of  oxygen  and  uric  acid  on  proteine,  48.  Of 
oxygen  on  starch  and  hippuric  acid,  48.  Of 
oxygen  and  water  on  proteine  and  starch,  49 
Of  oxygen  and  water  on  proteine  when  soda  ia 
absent,  49.  Of  the  separation  of  oxygen  from 
starch,  50.  Of  the  action  of  water  on  urea,  51. 
Of  the  action  of  water  and  oxygen  on  caffeine 
or  theine,  asparagine,  and  theobromine,  56. 

Proteine.  Discovered  by  Mulder,  36.  Its  com- 
position,  36.  Produced  alone  by  vegetables,  37. 
Is  the  source  of  all  the  organic  azotized  consti- 
tuents of  the  body,  37.  Its  formula,  41.  Its 
relation  to  fibrine,  albumen,  caseine,  and  all  the 
animal  tissues,  42.  Gelatine  no  longer  yields 
it,  although  formed  from  it,  43.  Its  relation  to 
bile  and  urine,  44.  Its  relation  to  allantoine 
and  choloidic  acid,  46  ;  to  gelatine,  46  ;  to  hip- 
puric acid,  48 ;  to  the  chief  secretions  and  ex- 
cretions,  48,  49;  to  fat,  49  Analysis  of  pro- 
teine from  the  crystalline  lens,  from  albumen, 
from  fibrine,  from  hair,  from  horn,  from  vegeta- 
ble albumen  and  fibrine,  from  cheese,  92. 

Prout.  His  analysis  of  starch,  88  ;  of  grape  su- 
gar from  honey,  88  ;  of  sugar  of  milk,  88 ;  of 
cane  sugar,  89  ;  of  urea,  90.  His  discovery  of 
free  muriatic  acid  in  the  gastric  juice,  38.  On 
the  effect  of  fat  food  on  the  urine,  45. 

Prussic  Acid.     See  Acid,  Hydrocyanic. 

Pulmonary  Diseases.  Arise  from  excess  of  oxy. 
gen,  16.  Prevail  in  winter,  17. 

Pulse.    Its  frequency  in  different  animals,  86. 

Putrefaction.  Is  a  process  of  transformation,  37. 
Membranes  very  liable  to  it,  38.  Effects  of  the 
putrefaction  of  green  food  in  the  stomach  of 
animals,  39.  Is  analogous  to  digestion,  40. 
Putrefying  animal  matters  cause  the  fermenta- 
tion of  sugar,  40.  Is  checked  by  empyreuma- 
tics,  41,  54. 

.Q. 

Quinine.  Contains  nitrogen,  56.  Its  analysis, 
100. 

R. 

Regnault.     His  analysis  of  morphia,  101. 

Reproduction  of  Tissues.     See  Nutrition. 
R 


110 


INDEX. 


Reproduction  of  the  Species,  20. 

Rhenish  Wines.  Contain  so  much  tartar,  that 
their,  use  prevents  the  formation  of  uric  acid 
calculus,  49. 

Respiration.  Theory  of,  77  et  seq.  Its  connexion 
with  the  food  and  with  animal  heat,  14  et  seq. 
S. 

Salt,  Common.  Essential  to  the  formation  of 
bile  in  the  herbivora,  and  to  that  of  gastric  juice, 
52  et  seq. 

Saussure,  De.  His  analysis  of  grape  sugar  and 
of  starch  sugar,  88,  of  wax,  92. 

Scherer,  Dr.  Jos.  His  analysis  of  albumen  from 
serum  of  blood,  87,  of  fibrine  of  blood,  87, 
of  vegetable  fibrine,  87,  of  vegetable  caseine,  88, 
of  animal  caseine,  88,  of  proteine  from  differ- 
ent sources,  92,  of  albumen  from  white  of  egg, 
92,  of  albumen  from  different  sources,  94,  of 
fibrine,  94,  of  gelatine  from  different  sources, 

94,  of  tissues  containing  chondrine,  95,  of  the 
tunica  media  of  arteries,  95,  of  horny  tissues, 

95,  of  the  lining  membrane  of  the  egg,  95,  of 
feathers,  95,  of  the  pigmentum  nigrum  oculi, 
95.     Results  of  his  researches,  42. 

Secretions.     See  Bile  and  Urine, 

Seguin.  His  calculation  of  the  amount  of  inspired 

oxygen,  80. 

Serpents.  Their  excrements  consist  of  urate  of 
ammonia,  24.  The  process  of  digestion  in 
them,  24. 

Sleep,  Theory  of,  68.   Amount  of  sleep  necessary 
for  the  adult,  the  infant,  and  the  old  man,  73  et 
seq.     Induced  by  alcohol  or  wine,  71. 
Soda.     Essential  to  blood  and  bile,  and  derived 

from  common  salt,  76  et  seq. 
Sodium,  Chloride  of.     See  Salt. 
Solanine.  Contains  nitrogen,  56.  Its  analysis,  100. 
Starch.     Exists  in  the  food  of  the  herbivora,  28. 
Is  convertible  into  sugar,  28,  29.     Its  relation 
to  gum  and  sugar,  29.     Its  function  in  food,  29 
et  seq.     Amount  of  carbon  in  starch  compared 
with  that  in  flesh,  30.     Its  composition  com- 
pared with  that  of  fat,  32,  33.     Is  the   source 
of  diabetic  sugar,  35.     Is  an  element  of  respi- 
ration, 35.     Dissolved  by  diastase,  38.     Its  re- 
lation to  choleic  acid,  48.     Its  relation   to  the 
principal  secretions  and  excretions,  49,  to  cho- 
loidic  acid,  51,  to  bile,  51,  52,  53.    Its  analysis 
from  fifteen  different  plants,  88. 
Starvation.  Process  of,  17.  Cause  of  death  in,  17. 
Strecker.     His  analysis  of  starch  from  twelve  dif- 
ferent plants,  88. 

Sugar.  Analysis  of  grape-sugar,  88,  of  sugar  of 
milk,  89,  of  cane  sugar,  90.  Is  an  element  of 
respiration,  35. 

Sulphur.  Exists  in  albumen,  and  caseine,  21,  42. 
Sulphuretted  Hydrogen.     Theory  of  its  poison- 
us  action,  80. 

>huric  Acid.     See  Acid,  Sulphuric, 
ply  of  matter.     See  Nutrition, 
ply  and  Waste.     Equilibrium  between  them 
institutes  the  abstract  state  of  health,  74,  75. 
ffects  of  its  disturbance,  75'  et  seq.      Means 
•  restoring  the  equilibrium,  73,  75  et  seq. 

T. 

3s  of  the  food  consumed  by  soldiers  of  Ger- 
jiy,  83.  Of  the  food  and  excretions  of  the 
•se  and  cow,  86. 

ne.  How  produced  from  bile,  44.  Its  re- 
on  to  choleic  acid,  44.  Its  relation  to  uric 
I  and  urea,  and  to  allantome,  49,  to  uric  acid 


50,  to  alloxan,  50,  to  choloidic  and  choleic  acids, 
and  ammonia,  51,  to  caffeine  or  theine,  56,  to 
asparagine,  56,  to  theobromine,  57. 

Temperature.  Its  effects  on  the  amount  of  in 
spired  oxygen,  15,  and  on  the  appetite,  15  ti 
seq.  A  slight  depression  of  temperature  causes 
death  in  aged  people,  75.  Temperature  of  the 
blood  in  different  animals,  87.  Temperature 
of  the  body  constantly  kept  up  by  internal 
causes,  15,  16. 

Tendons.     Analysis  of,  94. 

Thaulow.     His  analysis  of  cystic  oxide,  99. 

Theine.  Is  identical  with  caffeine,  56.  And 
with  guaranine,  57.  Theory  of  its  action,  57 
et  seq.  Its  relation  to  bile,  56.  Its  analysis, 
101. 

Theobromine.  Analogous  to  theine,  56.  Theory 
of  its  action,  57  et  seq.  Its  relation  to  bile,  56, 
57.  Its  analysis,  101. 

Theory.  Of  animal  heat,  15  et  seq.  Of  diges- 
tion, 37  et  seq.  Of  respiration,  77  et  seq.  Of 
the  motions  in  the  animal  organism,  60  et  seq. 
Of  disease,  74  et  seq.  Of  the  action  of  caffeine, 
&c.,  57  et  seq.  Of  the  action  of  the  vegetable 
alkalies,  57  et  seq.  Of  health,  74,  75. 

Tiedemann  and  Gmelin.  Their  attempt  to  sup- 
port a  goose  upon  albumen  alone,  unsuccessful, 
37. 

Tissues,  Metamorphosis  of:  see  Metamorphosiy. 
Analysis  of  the  animal  tissues,  94,  95.  Formu- 
las of,  42. 

Tobacco.  Arrests  or  retards  the  change  of  matter, 
56. 

Transformation.     See  Metamorphosis. 

Turnips.  Juice  of,  contains  vegetable  fibrine  and 
albumen,  22. 

U. 

Urea.  Derived  from  uric  acid,  45.  Also  from 
the  oxidation  of  blood,  45 ;  from  allantoine,  16. 
Its  relation  to  choleic  acid,  48;  to  hippuric 
acid,  48;  to  proteine,  48;  to  proteine  and 
starch,  49 ;  to  proteine  and  fat,  49 ;  to  taurine, 
50;  to  carbonate  of  ammonia,  51 ;  to  theobro- 
mine, 56.  Its  analysis,  98.  Occurs  in  the 
urine  of  those  who  have  taken  benzoic  acid 
along  with  hippuric  acid,  102. 

Urinary  Calculi.     See  Calculus. 

Uric  Acid.     See  Acid,  Uric. 
V. 

Varrentrapp  and  Will.  Their  analysis  of  ve- 
getable albumen,  87.  Of  sulphate  of  potash 
and  caseine,  88. 

Vegetables.  Alone  produce  compounds  of  pro- 
teincj  37.  Azotized  constituents  of,  nutritious, 
22:  medical  or  poisonous,  55.  Analysis  of 
those  vegetables  which  are  used  for  food,  82 
et  seq. 

Vegetable  Life.  Distinguished  from  nervous  life, 
20.  Predominates  in  the  early  stages  of  life, 
20.  Also  in  the  female,  20. 

Venous  Blood.     See  Blood. 

Vital  force,  or  vitality.  Definition  of,  1 1  et  seq 
Theory  of,  60  et  seq. 

Vogel.  His  analysis  of  gas  from  the  abdomen  of 
cattle  after  excess  in  green  food,  93. 

W. 

Water.  Is  one  of  the  two  constituents  of  the 
body  which  contain  no  nitrogen,  21.  Its  use 
as  a  solvent,  21.  Contributes  to  the  greater 
part  of  the  transformations  in  the  body,  44— 
57. 


INDEX. 


lu 


Wax.  On  its  production  from  honey  by  the  bee, 
90 — 92.  Its  an  lysis,  92. 

Wheat.  Contains  vegetable  fibrine,  22.  Ana- 
lysis of  fibrin^,  »lbumen,  and  gluten,  from 
wheat,  87. 

Will  and  ^tulr^  Their  analysis  of  lithofellic 
acid  100. 


Wine.  The  wines  of  the  south  promote  the 
formation  of  calculus,  45.  But  not  Rhenish 
wines,  45.  Theory  of  its  action,  72. 

Woskresensky  His  analysis  of  theobromine,  10L 
Y. 

Yams.     Analysis  of  starch  from,  88. 


FAMILIAE 


LETTERS  ON  CHEMISTRY, 


AND   ITS   RELATION   TO 


COMMERCE,  PHYSIOLOGY,  AND  AGRICULTURE. 


BY  BARON  JUSTUS  LIEBIG,  M,D,,  P.H.D.,  F1S,,  ILR.I.A, 

PROFESSOR  OF  CHEMISTRY  IN  THE    UNIVERSITY  OF  GIESSEN, 

AND 

AUTHOR    OF    "AGRICULTURAL   CHEMISTRY,"    "ANIMAL    CHEMISTRY," 
"MOTION  OF  JUICES  IN  ANIMAL  BODY,  AND  CURE  OF  THE   POTATO 
DISEASE/'  "  CIJEMISTRY  AND  PHYSICS  IN  RELATION  TO  PHY- 
SIOLOGY AND  PATHOLOGY,"  "  LETTERS  ON  CHEMISTRY," 
'  FIRST'   AND    '  SECOND   SERIES/  "  CHEM- 
ISTRY OF  FOOD,"  ETC.,  ETC. 


EDITED  BY  JOHN  GARDINER,  M.  D. 

MEMBER   OF   THE    CHEMICAL    SOCIETY. 

FROM  THE  LAST  LONDON  EDITION,  REVISED  AND  CORRECTED. 


T.  B.  PETERSON,  No.  102  CHESTNUT  STREET. 


PKEFACE. 


i  THE  letters  contained  in  this  little  Yolume  embrace  some  of  the  most  impor- 
tant points  of  the  science  of  Chemistry,  in  their  application  to  Natural  Phi- 
losophy, Physiology,  Agriculture  and  Commerce.  Some  of  them  treat  of 
subjects  which  have  already  been,  or  will  hereafter  be,  more  fully  discussed  in 
my  larger  works.  They  were  intended  to  be  mere  sketches,  and  were  written 
for  the  especial  purpose  of  exciting  the  attention  of  governments,  and  an  en- 
lightened public,  to  the  necessity  of  establishing  Schools  of  chemistry,  and 
of  promoting,  by  every  means,  the  study  of  a  science  so  intimately  connected 
with  the  arts,  pursuits,  and  social  well-being  of  modern  civilized  nations. 

For  my  own  part  I  do  not  scruple  to  avow  the  conviction,  that  ere  long, 
a  knowledge  of  the  principal  truth  of  Chemistry  will  be  expected  in  every 
educated  man,  and  that  it  will  be  as  necessary  to  the  Statesman  and  Political 
Economist,  and  the  Practical  Agriculturist,  as  it  is  already  indispensable  to 
the  Physician  and  the  Manufacturer. 

In  Germany,  such  of  these  Letters  as  have  been  already  published,  have 
not  failed  to  produce  some  of  the  results  anticipated.  New  professorships 
have  been  established  in  the  Universities  of  Gottingen  and  Wurtzburg,  for  the 
express  purpose  of  facilitating  the  application  of  chemical  truths  to  the  prac- 
tical arts  of  life,  and  of  following  up  the  new  line  of  investigation  and  re- 
search— the  bearing  of  Chemistry  upon  Physiology,  Medicine,  and  Agricul- 
ture,— which  may  be  said  to  be  only  just  begun. 

My  friend,  Dr.  Ernest  Dieffenbach,  one  of  my  first  pupils,  who  is  well 
acquainted  with  all  the  branches  of  Chemistry,  Physics,  Natural  History,  and 
Medicine,  suggested  to  me  that  a  collection  of  these  Letters  would  be  accepta- 
ble to  the  English  public,  which  has  so  favorably  received  my  former  works. 

I  readily  acquiesced  in  the  publication  of  an  English  edition,  and  undertook 
to  write  a  few  additional  Letters,  which  should  embrace  some  conclusions  I 
have  arrived  at,  in  my  recent  investigations,  in  connexion  with  the  application 
of  chemical  science  to  the  physiology  of  plants  and  agriculture. 

My  esteemed  friend,  Dr.  Gardner,  has  had  the  kindness  to  revise  the  manu- 
script and  the  proof-sheets  for  publication,  for  which  I  cannot  refrain  expressing 
my  best  thanks. 

It  only  remains  for  me  to  add  a  hope,  that  this  little  offering  may  serve  to 
make  new  friends  to  our  beautiful  and  useful  science,  and  be  a  remembrancer 
to  those  old  friends  who  have,  for  many  years  past,  taken  a  lively  interest  in 
all  my  labors. 


JUSTUS  LIEBIG. 
Giessen,  August,  1852. 

(2) 


CONTENTS. 


LETTER  I. 

The  Subject  proposed.  Materials  employed  for  Chemical  Apparatus :— - 
GLASS — CAOUTCHOUC — CORK — PLATINUM.  THE  BALANCE.  The 
"Elements"  of  the  Ancients,  represent  the  forms  of  matter.  Lavoi- 
sier and  his  successors.  Study  of  the  materials  composing  the  Earth. 
Synthetic  production  of  Minerals — LAPIS  LAZULI.  Organic  chemistry.  5 

LETTER   II. 

Changes  of  FORM  which  every  kind  of  Matter  undergoes.  Conversion 
of  Gases  into  Liquids  and  Solids.  Carbonic  Acid — its  curious  proper- 
ties in  a  solid  state.  Condensation  of  Gases  by  porous  bodies.  By 
Spongy  Platinum.  Importance  of  this  property  in  Nature  7 

LETTER  III. 

The  Manufacture  of  Soda  from  Culinary  Salt;  its  importance  in  the  Arts 
and  in  Commerce.  Glass — Soap — Sulphuric  Acid.  Silver  Refining. 
Bleaching.  TRADE  IN  SULPHUR  -  «?  :  -  •  -  10 

LETTER  IY. 

Connection  of  Theory  with  Practice.  Employment  of  MAGNETISM  as  a 
moving  power — its  impracticability.  Relation  of  Coals  and  Zinc  as 
economic  sources  of  Force.  Manufacture  of  Beet-root  Sugar — its  im- 
policy. GAS  for  illumination  -  -  13 

LETTER  Y. 

ISOMERISM,  or  Identity  of  composition  in  bodies  with  different  chemical 
and  physical  properties.  CRYSTALLIZATION.  AMORPHISM.  ISOMOR- 
PHISM, or  similarity  of  properties  in  bodies  totally  different  in  com- 
position *.;.  -  .*  -  -.  *  ;  V  ^;  •  •  -  16 

LETTER  VI. 

ALLIANCE  OP  CHEMISTRY  WITH  PHYSIOLOGY.  Division  of  FOOD  into 
nourishment,  and  materials  for  combustion.  Effects  of  Atmospheric 
Oxygen.  Balance  of  CARBON  and  OXYGEN  -  -  -  -  -  18 

LETTER  VII. 

ANIMAL  HEAT,  its  laws  and  influence  on  the  Animal  Functions.  Loss 
and  SUPPLY.  Influence  of  Climate.  Fuel  of  Animal  Heat.  Agency 
of  Oxygen  in  disease.  Respiration  •  <~  -  •  '•  *~  -  20 

LETTER  VIII. 

ALIMENTS.  Constituents  of  the  Blood.  Fibrine,  Albumen.  Inorganic 
Substances.  Isomerism  of  Fibrine,  Albumen,  and  elements  of  nutrition. 
Relation  of  animal  and  vegetable  organisms  -  -  24 

3 


CONTENTS. 


PAOB 

LETTER  IX. 

Growth  of  Animals.  Use  of  Butter  and  Milk.  Metamorphoses  of  Tis- 
sues. Food  and  Carnivora,  and  of  the  Horse  -  -  -  -  -27 

LETTER  X. 

Application  of  the  preceding  Facts  to  MAN.  Division  of  human  food. 
Uses  of  Gelatine  -  -  ,  •  «  y v  -  -  29 

LETTER  XI. 

CIRCULATION  OF  MATTER  IN  THE  ANIMAL  AND  VEGETABLE  KINGDOMS. 
The  Ocean.  AGRICULTURE.  RESTITUTION  or  AN  EQUILIBRIUM  IN 
THE  SOIL.  Causes  of  the  exhaustion  of  Land.  Virginia.  England. 
Relief  gained  by  importation  of  bones.  Empirical  Farming  unsatisfac- 
tory. Necessity  for  scientific  principles.  Influence  of  the  Atmosphere. 
Of  Saline  and  Earthy  matters  of  the  soil  -  -  ".-**'  -  31 

LETTER  XII. 

SCIENCE  AND  ART  OP  AGRICULTURE.  NECESSITY  OF  CHEMISTRY.  Ra- 
tionale of  agricultural  process.  Washing  for  Gold.  -  1_*.  •  34 

LETTER  XIII. 

ILLUSTRATION  OF  THE  NECESSITY  OF  CHEMISTRY  TO  ADVANCE  AND  PER- 
FECT AGRICULTURE.  Manner  in  which  FALLOW  ameliorates  the  soil. 
Use  of  Lime.  Effects  of  Burning.  Of  Marl  '/-  *H  ;  -  36 

LETTER  XIV. 

NATURE  AND  EFFECTS  OF  MANURES.  Animal  bodies  subject  to  constant 
waste.  Parts  separating — exuviae — waste  vegetable  matters — together 
contain  all  the  elements  of  the  soil  and  of  food.  Various  value  of  ex- 
crements of  different  animals  as  manure  -  -  -  V  t/*  5  *  •  ^8 

LETTER  XV. 

SOURCE  OF  THE  CARBON  AND  NITROGEN  OF  PLANTS.  Produce  of  Carbon 
in  Forests  and  Meadows  supplied  only  with  mineral  aliments  prove  it 
to  be  from  the  atmosphere.  Relations  between  Mineral  constituents, 
and  Carbon  and  Nitrogen.  Effects  of  the  Carbonic  Acid  and  Ammonia 
of  Manures.  Necessity  of  inorganic  constituents  to  the  formation  of 
aliments,  of  blood,  and  therefore  of  nutrition.  NECESSITY  of  IN- 
QUIRIES by  ANALYSIS  to  advance  AGRICULTURE  -  -  41 

LETTER  XVI. 

RESULTS  OF  THE  AUTHOR'S  LATEST  INQUIRIES.  Superlative  importance 
of  the  PHOSPHATES  OF  LIME  and  ALKALIES  to  the  cultivation  of  the 
CERALIA.  SOURCES  of  a  SUPPLY  of  these  MATERIALS  -  -  -  46 


FAMILIAR 


LETTERS  ON  CHEMISTRY; 


LETTER  I. 

MY  DEAR  SIR: 

The  influence  which  the  science  of  chemistry  exercises  upon  human  industry, 
agriculture,  and  commerce ;  upon  physiology,  medicine,  and  other  sciences,  is  now 
so  interesting  a  topic  of  conversation  every  where,  that  it  may  be  no  unacceptable 
present  to  you,  if  I  trace  in  a  few  familiar  letters,  some  of  the  relations  it  bears  to 
these  various  sciences,  and  exhibit  for  you  its  actual  effects  upon  the  present  social 
condition  of  mankind. 

In  speaking  of  the  present  state  of  chemistry,  its  rise  and  progress ;  I  shall  need 
no  apology,  if,  as  a  preliminary  step,  I  call  your  attention  to  the  implements  which 
the  chemist  employs — the  means  which  are  indispensable  to  his  labors  and  to  his 
success. 

These  consist,  generally,  of  materials  furnished  to  us  by  nature,  endowed  with 
many  most  remarkable  properties  fitting  them  for  our  purposes.  If  one  of  them  ia 
a  production  of  art,  yet  its  adaptation  to  the  use  of  mankind — the  qualities  which 
render  it  available  to  us — must  be  referred  to  the  same  source  as  those  derived 
immediately  from  nature. 

Cork,  platinum,  glass,  and  caoutchouc,  are  the  substances  to  which  I  allude, 
and  which  minister  so  essentially  to  modern  chemical  investigations.  Without 
them,  indeed,we  might  have  made  some  progress,  but  it  would  have  been  slow ; 
we  might  have  accomplished  much,  but  it  would  have  been  far  less  than  has  been 
done  with  their  aid.  Some  persons,  by  the  employment  of  expensive  substitutes, 
might  have  successfully  pursued  the  science  ;  but  incalculably  fewer  minds  would 
have  been  engaged  in  its  advancement.  These  materials  have  only  been  duly 
appreciated  and  fully  adopted  within  a  very  recent  period.  In  the  time  of  Lavoisier, 
the  rich  alone  could  make  chemical  researches  ;  the  necessary  apparatus  could  only 
be  procured  at  a  very  great  expense. 

And  first,  of  glass.  Every  one  is  familiar  with  most  of  the  properties  of  this 
curious  substance — its  transparency,  hardness,  destitution  of  color,  and  stability 
under  ordinary  circumstances.  To  these  obvious  qualities  we  may  add  those 
which  especially  adapt  it  to  the  use  of  the  chemist,  namely,  that  it  is  unaffected 
by  most  acids  or  other  fluids  contained  within  it.  At  certain  temperatures  it 
becomes  more  ductile  and  plastic  than  wax,  and  may  be  made  to  assume  in  our 
hands,  before  the  flame  of  a  common  lamp,  the  form  of  every  vessel  we  need 
to  contain  our  materials,  and  of  every  apparatus  required  to  pursue  our  ex- 
periments. 

(5) 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


Then,  how  admirable  and  valuable  are  the  properties  of  cork !  How  little  do 
men  reflect  upon  the  inestimable  worth  of  so  common  a  substance!  How  few 
rightly  esteem  the  importance  of  it  to  the  progress  of  science,  and  the  moral 
advancement  of  mankind !  There  is  no  production  of  nature  or  art  equally  adapted 
to  the  purposes  to  which  the  chemist  applies  it.  Cork  consists  of  a  soft,  highly 
elastic  substance,  as  a  basis,  having  diffused  throughout  a  matter  with  properties 
resembling  wax,  tallow,  and  resin,  yet  dissimilar  to  all  of  these,  and  termed 
wberin.  This  renders  it  perfectly  impermeable  to  fluids,  and,  in  a  great  measure, 
even  to  gases.  It  is  thus  the  fittest  material  we  possess  for  closing  our  bottles, 
and  retaining  their  contents.  By  its  means,  and  with  the  aid  of  caoutchouc,  we 
connect  our  vessels  and  tubes  of  glass,  and  construct  the  most  complicated  appa- 
ratus. We  form  joints  and  links  of  connexion,  adapt  large  apertures  to  small,  and 
thus  dispense  altogether  with  the  aid  of  the  brass-founder  and  the  mechanist.  Thus 
the  implements  of  the  chemist  are  cheaply  and  easily  procured,  immediately 
adapted  to  any  purpose,  and  readily  repaired  or  altered. 

Again ;  in  investigating  the  composition  of  solid  bodies — of  minerals — we  are 
under  the  necessity  of  bringing  them  into  a  liquid  state,  either  by  solution  or 
fusion.  Now  vessels  of  glass,  of  porcelain,  and  of  all  non-metallic  substances,  are 
destroyed  by  the  means  we  employ  for  that  purpose — are  acted  upon  by  many 
acids,  by  alkalies,  and  the  alkaline  carbonates.  Crucibles  of  gold  and  silver  would 
melt  at  high  temperatures.  But  we  have  a  combination  of  all  the  qualities  we  can 
desire,  in  platinum.  This  metal  was  only  first  adapted  to  these  uses  about  fifty 
years  since.  It  is  cheaper  than  gold,  harder  and  more  durable  than  silver,  infusible 
at  all  temperatures  ot  our  furnaces,  and  is  left  intact  by  acids  and  alkaline 
carbonates.  Platinum  unites  all  the  valuable*  properties  of  gold  and  of  porcelain, 
resisting  the  action  of  heat,  and  of  almost  all  chemical  agents. 

As  no  mineral  analysis  could  be  made  perfectly  without  platinum  vessels,  had  we 
not  possessed  this  metal,  the  composition  of  minerals  would  have  yet  remained 
unknown ;  without  cork  and  qaoutchouc  we  should  have  required  the  costly  aid  of 
the  mechanician  at  every  step.  Even  without  the  latter  of  these  adjuncts,  our  in- 
struments would  have  been  far  more  costly  and  fragile.  Possessing  all  these  giftd 
of  nature,  we  economize  incalculably  our  time — to  us  more  precious  than  money  ! 

Such  are  our  instruments.  An  equal  improvement  has  been  accomplished  in 
our  laboratory.  This  is  no  longer  the  damp,  cold,  fire-proof  vault  of  the  metallur- 
gist, nor  the  manufactory  of  the  druggist,  fitted  up  with  stills  and  retorts.  On  the 
contrary,  a  light,  warm,  comfortable  room,  where  beautifully  constructed  lamps 
supply  the  place  of  furnaces,  and  the  pure  and  odorous  flame  of  gas,  or  of  spirits 
of  wine,  supersedes  coal  and  other  fuel,  and  gives  us  all  the  fire  we  need ;  where 
health  is  not  invaded,  nor  the  free  exercise  of  thought  impeded;  there  we  pursue 
our  inquiries,  and  interrogate  nature  to  reveal  her  secrets. 

To  these  simple  means  must  be  added  the  balance,  and  then  we  possess  every 
thing  which  is  required  for  the  most  extensive  researches. 

The  great  distinction  between  the  manner  of  proceeding  in  chemistry  and  natural 
philosophy,  is,  that  one  weighs,  the  other  measures.  The  natural  philosopher 
has  applied  his  measures  to  nature  for  many  centuries,  but  only  for  fifty  years 
have  we  attempted  to  advance  our  philosophy  by  weighing. 

For  all  great  discoveries  chemists  are  indebted  to  the  balance — that  incomparable 
instrument  which  gives  permanence  to  every  observation,  dispels  all  ambiguity, 
establishes  truth,  detects  error,  and  guides  us  in  the  true  path  of  inductive  science. 

The  balance,  once  adopted  as  a  means  of  investigating  nature,  put  an  end  to 
the  school  of  Aristotle  in  physics.  The  explanation  of  natural  phenomena  by  mere 
fanciful  speculations,  gave  place  to  a  true  natural  philosophy.  Fire,  air,  earth, 
and  water,  could  no  longer  be  regarded  as  elements.  Three  of  them  could  hence- 
forth be  considered  only  as  significative  of  the  forms  in  which  all  matter  exists. 
Every  thing  with  which  we  are  conversant  upon  the  surface  of  the  earth  is  solid, 
liquid,  or  aeriform  ;  but  the  notion  of  the  elementary  nature  of  air,  earth,  and 
water,  so  universally  held,  was  now  discovered  to  belong  to  the  errors  of  the  past. 

Fire  was  found  to  be  but  the  visible  and  perceptible  indication  of  changes 
proceeding  within  the  so-called  elements. 

Lavoisier  investigated  the  composition  of  the  atmosphere  and  of  water,  and 
studied  the  many  wonderful  offices  performed  by  an  element  common  to  both  in  the 
scheme  of  nature,  namely,  oxygen :  and  he  discovered  many  of  the  properties  of 
this  elementary  gas. 

After  his  time,  the  principal  problem  of  chemical  philosophers  was  to  determine 
the  composition  of  the  solid  matters  composing  the  earth.  To  the  eighteen  metals 
previously  known,  were  soon  added,  twenty-four  discovered  to  be  constituents  of 
minerals.  The  great  mass  of  the  earth  was  shown  to  be  composed  of  metals  in 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


combination  with  oxygen,  to  which  they  are  united  in  one,  two,  or  more  definite 
and  unalterable  proportions,  forming  compounds  which  are  termed  metallic  oxides, 
and  these  again,  combined  with  oxides  of  other  bodies,  essentially  different  to 
metals,  namely,  carbon,  and  silicium.  If  to  these  we  add  certain  compounds  of 
sulphur  with  metals,  in  which  the  sulphur  takes  the  place  of  oxygen,  and  forms 
sulphurets,  and  one  other  body — common  salt — (which  is  a  compound  of  sodium 
and  chlorine,)  we  have  every  substance  which  exists  in  a  solid  form  upon  our  globe 
in  any  very  considerable  mass.  Other  compounds,  innumerably  various,  are  found 
only  in  small  scattered  quantities. 

The  chemist,  however,  did  not  remain  satisfied  with  the  separation  of  minerals 
into  their  component  elements,  i.  e.,  their  analysis ;  but  he  sought  by  synthesis 
(i.  e.,  by  combining  the  separate  elements  and  forming  substances  similar  to  those 
constructed  by  nature),  to  prove  the  accuracy  of  his  processes  and  the  correctness 
of  his  conclusions.  Thus  he  formed,  for  instance,  pumice-stone,  feld-spar,  mica, 
iron  pyrites,  &c.,  artificially. 

But  of  all  the  achievements  of  inorganic  chemistry  the  artificial  formation  of 
lapis  lazuli  was  the  most  brilliant  and  the  most  conclusive.  This  mineral,  as 
presented  to  us  by  nature,  is  calculated  powerfully  to  arrest  our  attention  by  its 
beautiful  azure-blue  color,  its  remaining  unchanged  by  exposure  to  air  or  to  fire, 
and  furnishing  us  with  a  most  valuable  pigment,  Ultramarine,  more  precious  than 
gold ! 

The  analysis  of  lapis  lazuli  represented  it  to  be  composed  of  silica,  alumina, 
and  soda,  three  colorless  bodies,  with  sulphur  and  a  trace  of  iron.  Nothing  could 
be  discovered  in  it  of  the  nature  of  a  pigment,  nothing  to  which  its  blue  color  could 
be  referred,  the  cause  of  which  was  searched  for  in  vain.  It  might  therefore  have 
been  supposed  that  the  analyst  was  here  altogether  at  fault,  and  that  at  any  rate 
its  artificial  production  must  be  impossible.  Nevertheless,  this  has  been  accom- 
plished, and  simply  by  combining  in  the  proper  proportions,  as  determined  by 
analysis,  silica,  alumina,  soda,  iron,  and  sulphur.  Thousands  of  pounds  weight  are 
now  manufactured  from  these  ingredients,  and  this  artificial  ultramarine  is  as 
beautiful  as  the  natural,  while  for  the  price  of  a  single  ounce  of  the  latter  we 
may  obtain  many  pounds  of  the  former. 

With  the  production  of  artificial  lapis  lazuli,  the  formation  of  mineral  bodies 
by  synthesis  ceased  to  be  a  scientific  problem  to  the  chemist ;  he  has  no  longer 
sufficient  interest  in  it  to  pursue  the  subject.  He  may  now  be  satisfied  that  ana- 
lysis will  reveal  to  him  the  true  constitution  of  minerals.  But  to  the  mineralogist 
and  geologist  it  is  still  in  a  great  measure  an  unexplored  field,  offering  inquiries 
of  the  highest  interest  and  importance  to  their  pursuits. 

After  becoming  acquainted  with  the  constituent  elements  of  all  the  substances 
within  our  reach,  and  the  mutual  relations  of  these  elements,  the  remarkable 
transmutations  to  which  bodies  are  subject  under  the  influence  of  the  vital  powers 
of  plants  and  animals,  became  the  principal  object  of  chemical  investigations,  and 
the  highest  point  of  interest.  A  new  science,  inexhaustible  as  life  itself,  is  here 
presented  us,  standing  upon  the  sound  and  solid  foundation  of  a  well  established 
inorganic  chemistry.  Thus  the  progress  of  science  is,  like  the  development  of 
nature's  works,  gradual  and  expansive.  After  the  buds  and  branches  spring  forth 
the  leaves  and  blossoms,  after  the  blossoms  the  fruit. 

Chemistry,  in  its  application  to  animals  and  vegetables,  endeavors  jointly  with 
physiology  to  enlighten  us  respecting  the  mysterious  processes  and  sources  of 
organic  life. 


LETTER    II. 

MY  DEAR  SIR  : 

In  my  former  letter  I  reminded  you  that  three  of  the  supposed  elements  of 
the  ancients  represent  the  forms  or  state  in  which  all  the  ponderable  matter  of  our 
globe  exists  ;  I  would  now  observe,  that  no  substance  possesses  absolutely  any  one 
of  those  conditions  ;  that  modern  chemistry  recognises  nothing  unchangeably  solid, 
liquid,  or  aeriform :  means  have  been  devised  for  effecting  a  change  of  state  in 
almost  every  known  substance.  Platinum,  alumina,  and  rock  crystal,  it  is  true, 
cannot  be  liquefied  by  the  most  intense  heat  of  our  furnaces,  but  they  melt  like 


3  FAMILIAR  LETTERS  ON  CHEMISTRY. 

wax  before  the  flame  of  the  oxy-hydrogen  blowpipe.  On  the  other  hand,  of  the 
twenty-eight  gaseous  bodies  with  which  we  are  acquainted,  twenty-five  may  be 
reduced  to  a  liquid  state,  and  one  into  a  solid.  Probably,  ere  long,  similar  changes 
of  condition  will  be  extended  to  every  form  of  matter. 

There  are  many  things  relating  to  this  condensation  of  the  gases  worthy  of 
your  attention.  Most  aeriform  bodies,  when  subjected  to  compression,  are  made 
to  occupy  a  space  which  diminishes  in  the  exact  ratio  of  the  increase  of  the  com- 
pressing force.  Very  generally,  under  a  force  double  or  triple  of  the  ordinary 
atmospheric  pressure  they  become  one  half  or  one  third  their  former  volume.  This 
was  a  long  time  considered  to  be  a  law,  and  known  as  the  law  of  Marriotte  ;  but  a 
more  accurate  study  of  the  subject  has  demonstrated  that  this  law  is  by  no  means 
of  gen  eral  application.  The  volume  of  certain  gases  does  not  decrease  in  the  ratio 
of  the  increase  of  the  force  used  to  compress  them,  but  in  some,  a  diminution  of 
their  bulk  takes  place  in  a  far  greater  degree  as  the  pressure  increases. 

Again,  if  ammoniacal  gas  is  reduced  by  a  compressing  force  to  one  sixth  of 
its  volume,  or  carbonic  acid  is  reduced  to  one  thirty-sixth,  a  portion  of  them  loses 
entirely  the  form  of  a  gas,  and  becomes  a  liquid,  which,  when  the  pressure  is 
withdrawn,  assumes  again  in  an  instant  its  gaseous  state — another  deviation  from 
the  law  of  Marriotte. 

Our  process  for  reducing  gases  into  fluids  is  of  admirable  simplicity.  A  simple 
bent  tube,  or  a  reduction  of  temperature  by  artificial  means,  have  superseded  the 
powerful  compressing  machines  of  the  isarly  experimenters. 

The  cyanuret  of  mercury,  when  heated  in  an  open  glass  tube,  is  resolved  into 
cyanogen  gas  and  metallic  mercury  ;  if  this  substance  is  heated  in  a  tube  hermeti- 
cally sealed,  the  decomposition  occurs  as  before,  but  the  gas,  unable  to  escape,  and 
shut  up  in  a  space  several  hundred  times  smaller  than  it  would  occupy  as  gas 
under  the  ordinary  atmospheric  pressure,  becomes  a  fluid  in  that  part  of  the  tube 
which  is  kept  cool. 

When  sulphuric  acid  is  poured  upon  limestone  in  an  open  vessel,  carbonic  acid 
escapes  with  effervescence  as  a  gas  ;  but  if  the  decomposition  is  effected  in  a  strong, 
close,  and  suitable  vessel  of  iron,  we  obtain  the  carbonic  acid  in  the  state  of  liquid. 
In  this  manner  it  may  be  obtained  in  considerable  quantities,  even  many  pounds 
weight.  Carbonic  acid  is  separated  from  other  bodies  with  which  it  is  combined  as 
a  fluid  under  a  pressure  of  thirty-six  atmospheres. 

The  curious  properties  of  fluid  carbonic  acid  are  now  generally  known.  When 
a  small  quantity  is  permitted  to  escape  into  the  atmosphere,  it  assumes  its  gaseous 
state  with  extraordinary  rapidity,  and  deprives  the  remaining  fluid  of  caloric  so 
rapidly  that  it  congeals  into  a  white  crystalline  mass  like  snow :  at  first,  it  was 
indeed  thought  to  be  really  snow,  but  upon  examination  it  proved  to  be  pure  frozen 
carbonic  acid.  This  solid,  contrary  to  expectation,  exercises  only  a  feeble  pressure 
upon  the  surrounding  medium.  The  fluid  acid  enclosed  in  a  glass  tube  rushes  at 
once,  when  opened,  into  a  gaseous  state,  with  an  explosion  which  shatters  the  tube 
into  fragments  ;  but  solid  carbonic  acid  can  be  handled  without  producing  any 
other  effect  than  a  feeling  of  intense  cold.  The  particles  of  the  carbonic  acid  being 
so  closely  approximated  in  the  solid,  the  whole  force  of  cohesive  attraction  (which 
in  the  fluid  is  weak)  becomes  exerted,  and  opposes  its  tendency  to  assume  its 
gaseous  state ;  but  as  it  receives  heat  from  surrounding  bodies,  it  passes  into  gas 
gradually  and  without  violence.  The  transition  of  solid  carbonic  acid  into  gas 
deprives  all  around  it  of  caloric  so  rapidly  and  to  so  great  an  extent,  that  a  degree 
of  cold  is  produced  immeasurably  great,  the  greatest  indeed  known.  Ten,  twenty, 
or  more  pounds  weight  of  mercury,  brought  into  contact  with  a  mixture  of  ether 
and  solid  carbonic  acid,  become  in  a  few  moments  firm  and  malleable.  This,  how- 
ever, cannot  be  accomplished  without  considerable  danger.  A  melancholy  accident 
occurred  at  Paris,  which  will  probably  prevent  for  the  future  the  formation  of 
solid  carbonic  acid  in  these  large  quantities,  and  deprive  the  next  generation  of 
the  gratification  of  witnessing  these  curious  experiments.  Just  before  the  com- 
mencement of  the  lecture  in  the  Laboratory  of  the  Polytechnic  School,  an  iron 
cylinder,  two  feet  and  a  half  long  and  one  foot  in  diameter,  in  which  carbonic  acid 
had  been  developed  for  experiment  before  the  class,  burst,  and  its  fragments  were 
scattered  about  with  the  most  tremendous  force ;  it  cut  off  both  the  legs  of  the 
assistant  and  killed  him  on  the  spot.  This  vessel,  formed  of  the  strongest  cast  iron, 
and  shaped  like  a  cannon,  had  often  been  employed  to  exhibit  experiments  in  the 
presence  of  the  students.  We  can  scarcely  think,  without  shuddering,  of  the 
dreadful  calamity  such  an  explosion  would  have  occasioned  in  a  hall  filled  with 
spectators. 

When  we  had  ascertained  the  fact  of  gases  becoming  fluid  under  the  influence 
of  cold  or  pressure,  a  curious  property  possessed  by  charcoal,  that  of  absorbing 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


gas  to  the  extent  of  many  times  its  volume,  —  ten,  twenty,  or  even,  as  in  the  case 
of  ammoniacal  gas  or  muriatic  acid  gas,  eighty  or  ninety  fold  —  which  had  been 
long  known,  no  longer  remained  a  mystery.  Some  gases  are  absorbed  and  con- 
densed within  the  pores  of  the  charcoal,  into  a  space  several  hundred  times  smaller 
than  they  before  occupied  ;  and  there  is  now  no  doubt  they  there  become  fluid,  or 
assume  a  solid  state.  As  in  a  thousand  other  instances,  chemical  action  here  sup- 
plants mechanical  forces.  Adhesion  or  heterogeneous  attraction,  as  it  is  termed,  ac- 
quired by  this  discovery  a  more  extended  meaning;  it  had  never  before  been 
thought  of  as  a  cause  of  change  of  state  in  matter  ;  but  it  is  now  evident  that  a  gas 
adheres  to  the  surface  of  a  solid  body  by  the  same  force  which  condenses  it  into  a 
liquid. 

The  smallest  amount  of  a  gas  —  atmospheric  air  for  instance—  can  be  compressed 
into  a  space  a  thousand  times  smaller  by  mere  mechanical  pressure,  and  then  its 
bulk  must  be  to  the  least  measurable  surface  of  a  solid  body,  as  a  grain  of  sand 
to  a  mountain.  By  the  mere  effect  of  mass  —  the  force  of  gravity  —  gaseous  mole- 
cules are  attracted  by  solids  and  adhere  to  their  surfaces  ;  and  when  to  this  physical 
force  is  added  the  feeblest  chemical  affinity,  the  liquefiable  gases  cannot  retain  their 
gaseous  state.  The  amount  of  air  condensed  by  these  forces  upon  a  square  inch 
of  surface  is  certainly  not  measurable  ;  but  when  a  solid  body,  presenting  several 
hundred  square  feet  of  surface  within  the  space  of  a  cubic  inch,  is  brought  into 
a  limited  volume  of  gas,  we  may  understand  why  that  volume  is  diminished, 
why  all  gases  without  exception  are  absorbed.  A  cubic  inch  of  charcoal  must 
have,  at  the  lowest  computation,  a  surface  of  one  hundred  square  feet.  This 
property  of  absorbing,  gases  varies  with  different  kinds  of  charcoal:  it  is  pos- 
sessed in  a  higher  degree  by  those  containing  the  most  pores,  that  is,  where  the 
pores  are  finer  ;  and  in  a  lower  degree  in  the  more  spongy  kinds,  that  is,  where 
the  pores  are  larger. 

In  this  manner  every  porous  body  —  rocks,  stones,  the  clods  of  the  fields,  &c.  —  im- 
bibe air,  and  therefore  oxygen  ;  the  smallest  solid  molecule  is  thus  surrounded  by 
its  own  atmosphere  of  condensed  oxygen  ;  and  if  in  their  vicinity  other  bodies 
exist  which  have  an  affinity  for  oxygen,  a  combination  is  effected.  When,  for  in- 
stance, carbon  and  hydrogen  are  thus  present,  they  are  converted  into  nourishment 
for  vegetables  —  into  carbonic  acid  and  water.  The  development  of  heat  when 
air  is  imbibed,  and  the  production  of  steam  when  the  earth  is  moistened  by 
rain,  are  acknowledged  to  be  consequences  of  this  condensation  by  the  action  of 
surfaces. 

But  the  most  remarkable  and  interesting  case  of  this  kind  of  action  is  the  imbi- 
bition of  oxygen  by  metallic  platinum.  This  metal,  when  massive,  is  of  a  lus- 
trous white  color,  but  it  may  be  brought,  by  separating  it  from  its  solutions,  into 
so  finely  divided  a  state,  that  its  particles  no  longer  reflect  light,  and  it  forms  a 
powder  as  black  as  soot.  In  this  condition  it  absorbs  eight  hundred  times  its 
volume  of  oxygen  gas,  and  this  oxygen  must  be  contained  within  it  in  a  state  of 
condensation  very  like  that  of  fluid  water. 

When  gases  are  thus  condensed,  that  is,  their  particles  made  to  approximate  in 
this  extraordinary  manner,  their  properties  can  be  palpably  shown.  Their  chemical 
actions  become  apparent  as  their  physical  characteristic  disappears.  The  latter 
consists  in  the  continual  tendency  of  their  particles  to  separate  from  each  other  ; 
and  it  is  easy  to  imagine  that  this  elasticity  of  gaseous  bodies  is  the  principal 
impediment  to  the  operation  of  their  chemical  force  ;  for  this  becomes  more  ener- 
getic as  their  particles  approximate.  In  that  state  in  which  they  exist  within 
the  pores  or  upon  the  surface  of  solid  bodies,  their  repulsion  ceases,  and  their 
whole  chemical  action  is  exerted.  Thus  combinations  which  oxygen  cannot  enter 
into,  decompositions  which  it  cannot  effect  while  in  the  state  of  gas,  take  place 
with  the  greatest  facility  in  the  pores  of  platinum  containing  condensed  oxygen. 
When  a  jet  of  hydrogen  gas,  for  instance,  is  thrown  upon  spungy  platinum,  it  com- 
bines with  the  oxygen  condensedvin  the  interior  of  the  mass  ;  at  their  point  of 
contact  water  is  formed,  and  as  the  immediate  consequence  heat  is  evolved  ;  the 
platinum  becomes  red  hot  and  the  gas  is  inflamed.  If  we  interrupt  the  current  of 
the  gas,  the  pores  of  the  platinum  become  instantaneously  filled  again  with 
oxygen  ;  and  the  same  phenomena  can  be  repeated  a  second  time,  and  so  on 
interminably. 

In  finely  pulverized  platinum,  and  even  in  spongy  platinum,  we  therefore  pos- 
sess a  perpetuum  mobile  —  a  mechanism  like  a  watch  which  runs  out  and  winds 
itself  up  —  a  force  which  is  never  exhausted  —  competent  to  produce  effects  of  the 
most  powerful  kind,  and  self-renewed  ad  infinitum. 

Many  phenomena,  formerly  inexplicable,  are  satifactorily  explained  by  these  re- 
cently discovered  properties  of  porous  bodies.  The  metamorphosis  of  alcohol  into 


10  FAMILIAR  LETTERS  ON  CHEMISTRY. 

acetic  acid,  by  the  process  known  as  the  quick  vinegar  manufacture,  depends  upon 
principles,  at  a  knowledge  of  which  we  have  arrived  by  a  careful  study  of  these 
properties. 


LETTER   III. 

MY  DEAR  SIR: 

The  manufacture  of  soda  from  common  culinary  salt  may  be  regarded  as 
the  foundation  of  all  our  modern  improvements  in  the  domestic  arts  ;  and  we  may 
take  it  as  affording  an  excellent  illustration  of  the  dependence  of  the  various 
branches  of  human  industry  and  commerce  upon  each  other,  and  their  relation  to 
chemistry. 

Soda  has  been  used  from  time  immemorial  in  the  manufacture  of  soap  and  glass, 
two  chemical  productions,  which  employ  and  keep  in  circulation  an  immense 
amount  of  capitaL  The  quantity  of  soap  consumed  by  a  nation  would  be  no  in- 
accurate measure  whereby  to  estimate  its  wealth  and  civilization.  Of  two  coun- 
tries with  an  equal  amount  of  population,  the  wealthiest  and  most  highly  civil- 
ized will  consume  the  greatest  weight  of  soap.  This  consumption  does  not 
subserve  sensual  gratification,  nor  depend  upon  fashion,  but  upon  the  feeling 
of  the  beauty,  comfort,  and  welfare,  attendant  upon  cleanliness ;  and  a  regard  to 
this  feeling  is  coincident  with  wealth  and  civilization.  The  rich  in  the  middle 
ages  concealed  a  want  of  cleanliness  in  their  clothes  and  persons,  under  a  pro- 
fusion of  costly  scents  and  essences,  while  they  were  more  luxurious  in  eating 
and  drinking,  in  apparel  and  horses.  With  us  a  want  of  cleanliness  is  equiva- 
lent to  insupportable  misery  and  misfortune. 

Soap  belongs  to  those  manufactured  products,  the  money-value  of  which  conti- 
nually disappears  from  circulation,  and  requires  to  be  continually  renewed.  It  is 
one  of  the  few  substances  which  are  entirely  consumed  by  use,  leaving  no  product 
of  any  worth.  Broken  glass  and  bottles  are  by  no  means  absolutely  worthless ; 
for  rags  we  may  purchase  new  cloth,  but  soap-water  has  no  value  whatever.  It 
would  be  interesting  to  know  .accurately  the  amount  of  capital  involved  in  the 
manufacture  of  soap  ;  it  is  certainly  as  large  as  that  employed  in  the  coffee  trade, 
with  this  important  difference  as  respects  Germany,  that  it  is  entirely  derived 
from  our  own  soil.  France  formerly  imported  soda  from  Spain,  Spanish  soda  being 
of  the  best  quality,  at  an  annual  expenditure  of  twenty  to  thirty  millions  of  francs. 
During  the  war  with  England,  the  price  of  soda,  and  consequently  of  soap  and 
glass,  rose  continually ;  and  all  manufactures  suffered  in  consequence. 

The  present  method  of  making  soda  from  common  salt  was  discovered  by  Le 
Blanc,  at  the  end  of  the  last  century.  It  was  a  rich  boon  for  France,  and  became 
of  the  highest  importance  during  the  war  of  Napoleon.  In  a  very  short  time  it  was 
manufactured  to  an  extraordinary  extent,  especially  at  the  seat  of  the  soap  manu- 
factories. Marseilles  possessed  for  a  time  a  monopoly  of  soda  and  soap.  The  policy 
of  Napoleon  deprived  that  city  of  the  advantages  derived  from  this  great  source 
of  commerce,  and  thus  excited  the  hostility  of  the  population  to  his  dynasty,  which 
became  favorable  to  the  restoration  of  the  Bourbons.  A  curious  result  of  an 
improvement  in  a  chemical  manufacture !  It  was  not  long,  however,  in  reaching 
England. 

In  order  to  prepare  the  soda  of  commerce  (which  is  the  carbonate)  from  common 
salt,  it  is  first  converted  into  Glauber's  salt  (sulphate  of  soda).  For  this  purpose 
eighty  pounds  weight  of  concentrated  sulphuric  acid  (oil  of  vitriol)  are  required 
to  one  hundred  pounds  of  common  salt.  The  duty  upon  salt  checked,  for  a  short 
time,  the  full  advantage  of  this  discovery ;  but  when  the  government  repealed  the 
duty,  and  its  price  was  reduced  to  its  minimum,  the  cost  of  soda  depended  upon 
that  of  sulphuric  acid. 

The  demand  for  sulphuric  acid  now  increased  to  an  immense  extent ;  and,  to 
supply  it,  capital  was  embarked  abundantly,  as  it  afforded  an  excellent  remune- 
ration. The  origin  and  formation  of  sulphuric  acid  was  studied  most  carefully ; 
and  from  year  to  year,  better,  simpler,  and  cheaper  methods  for  making  it  were 
discovered.  With  every  improvement  in  the  mode  of  manufacture,  its  price  fell ; 
«id  its  sale  increased  in  an  equal  ratio. 

.Sulphuric  acid  is  now  manufactured  in  leaden  chambers,  of  such  magnitude  that 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


they  would  contain  the  whole  of  an  ordinary  sized  house.  As  regards  the  process 
and  the  apparatus,  this  manufacture  has  reached  its  acme  —  scarcely  is  either 
susceptible  of  improvement.  The  leaden  plates  of  which  the  chambers  are  con- 
structed, requiring  to  be  joined  together  with  lead  (since  tin  or  solder  would  be 
acted  on  by  the  acid),  this  process  was,  until  lately,  as  expensive  as  the  plates 
themselves  ;  but  now,  by  means  of  the  oxy-hydrogen  blowpipe,  the  plates  are 
cemented  together  at  their  edges,  by  mere  fusion,  without  the  intervention  of  any 
kind  of  solder. 

And  then,  as  to  the  process  ;  according  to  theory,  one  hundred  pounds  weight  of 
sulphur  ought  to  produce  three  hundred  and  six  pounds  of  sulphuric  acid  ;  in  prac- 
tice, three  hundred  pounds  are  actually  obtained  ;  the  amount  of  loss  is  therefore 
too  insignificant  for  consideration. 

Again  ;  saltpetre  being  indispensable  in  making  sulphuric  acid,  the  commercial 
value  of  that  salt  had  formerly  an  important  influence  upon  its  price.  It  is  true 
that  one  hundred  pounds  of  saltpetre  only  are  required  to  one  thousand  pounds  of 
sulphur  ;  but  its  cost  was  four  times  greater  than  an  equal  weight  of  the  latter. 

Travellers  had  observed,  near  the  small  seaport  of  Yquiqui,  in  the  district  of 
Atacama,  in  Peru,  an  efflorescence  covering  the  ground  over  extensive  districts. 
This  was  found  to  consist  principally  of  nitrate  of  soda.  Advantage  was  quickly 
taken  of  this  discovery.  The  quantity  of  this  valuable  salt  proved  to  be  inex 
haustible,  as  it  exists  in  beds  extending  over  more  than  200  square  miles.  It 
was  brought  to  England  at  less  than  half  the  freight  of  the  East  India  saltpetre 
(nitrate  of  potassa)  ;  and  as,  in  the  chemical  manufacture,  neither  the  potash  nor 
the  soda  were  required,  but  only  the  nitric  acid,  in  combination  with  the  alkali, 
the  soda-saltpetre  of  South  America  soon  supplanted  the  potash-nitre  of  the  East. 
The  manufacture  of  sulphuric  acid  received  a  new  impulse  ;  its  price  was  much 
diminished  without  injury  to  the  manufacturer  ;  and,  with  the  exception  of  fluc- 
tuations, caused  by  the  impediments  thrown  in  the  way  of  the  export  of  sulphur 
from  Sicily,  it  soon  became  reduced  to  a  minimum,  and  remained  stationary. 

Potash-saltpetre  is  now  only  employed  in  the  manufacture  of  gunpowder  ;  it 
is  no  longer  in  demand  for  other  purposes  ;  and  thus,  if  Government  effect  a  saving 
of  many  hundred  thousand  pounds  annually  in  gunpowder,  this  economy  must  be 
attributed  to  the  increased  manufacture  of  sulphuric  acid. 

We  may  form  an  idea  of  the  amount  of  sulphuric  acid  consumed,  when  we  find 
that  50,000  pounds  weight  are  made  by  a  small  manufactory,  and  from  200,000  to 
600,000  pounds  by  a  large  one,  annually.  This  manufacture  causes  immense  sums 
to  flow  annually  into  Sicily.  It  has  introduced  industry  and  wealth  into  the  arid 
and  desolate  districts  of  Atacama.  It  has  enabled  us  to  obtain  platina  from  its 
ores  at  a  moderate,  and  yet  remunerating  price  ;  since  the  vats  employed  for  con- 
centrating this  acid,  are  constructed  of  this  metal,  and  cost  from  1000Z.  to  2000Z. 
sterling.  It  leads  to  frequent  improvements  in  the  manufacture  of  glass,  which 
continually  becomes  cheaper  and  more  beautiful.  It  enables  us  to  return  to  our 
fields  all  their  potash  —  a  most  valuable  and  important  manure  —  in  the  form  of 
ashes,  by  substituting  soda  in  the  manufacture  of  glass  and  soap. 

It  is  impossible  to  trace,  within  the  compass  of  a  letter,  all  the  ramifications  of 
this  tissue  of  changes  and  improvements  resulting  from  one  chemical  manufacture  ; 
but  I  must  still  claim  your  attention  to  a  few  more  of  its  most  important  and  imme- 
diate results.  I  have  already  told  you,  that  in  the  manufacture  of  soda  from  culi- 
nary salt,  it  is  first  converted  into  sulphate  of  soda.  In  this  first  part  of  the 
process,  the  action  of  sulphuric  acid  produces  primary  muriatic  acid  to  the  extent 
of  one  and  a  half  the  amount  of  the  sulphuric  acid  employed.  At'  first,  the  profit 
upon  the  soda  was  so  great  that  no  one  took  the  trouble  to  collect  the  muriatic 
acid  ;  indeed  it  had  no  commercial  value.  A  profitable  application  of  it  was,  how- 
ever, soon  discovered  :  it  is  a  compound  of  chlorine,  and  this  substance  may  be 
obtained  from  it  purer  than  from  any  other  source.  The  bleaching  power  of 
chlorine  has  long  been  known  ;  but  it  was  only  employed  upon  a  large  scale  after  it 
was  obtained  from  residuary  muriatic  acid,  and  it  was  found  that  in  combination 
with  lime,  it  could  be  transported  to  distances  without  inconvenience.  Thence- 
forth it  was  used  for  bleaching  cotton  ;  and,  but  for  this  new  bleaching  process,  it 
would  scarcely  have  been  possible  for  the  cotton  manufacture  of  Great  Britain 
to  have  attained  its  present  enormous  extent  —  it  could  not  have  competed  in  price 
with  France  and  Germany.  In  the  old  process  for  bleaching,  every  piece  must  be 
exposed  to  the  air  and  light  during  several  weeks  in  the  summer,  and  kept  con- 
tinually moist  by  manual  labor.  For  this  purpose,  meadow  land,  suitably  situa- 
ted, was  essential.  But  a  single  establishment,  near  Glasgow,  bleaches  1,400 
pieces  of  cotton  daily,  throughout  the  year.  What  an  enormous  capital  would 
be  required  to  purchase  land  for  this  purpose  !  How  greatly  would  it  increase  the 


12  FAMILIAR  LETTERS  ON  CHEMISTRY. 

cost  of  bleaching  to  pay  interest  upon  this  capital,  or  to  hire  so  much  land  in  Eng- 
land !  This  expense  would  scarcely  have  been  felt  in  Germany.  Beside  the  dimin- 
ished expense,  the  cotton  stuffs  bleached  with  chlorine,  suffer  less  in  the  hands  of 
skilful  workmen,  than  those  bleached  in  the  sun  ;  and  already  the  peasantry  in 
some  parts  of  Germany  have  adopted  it,  and  find  it  advantageous. 

Another  use  to  which  cheap  muriatic  acid  is  applied,  is  the  manufacture  of  glue 
from  bones.  Bone  contains  from  30. to  36  per  cent,  of  earthy  matter — chiefly  phos- 
phate of  lime,  and  the  remainder  is  gelatine.  When  bones  are  digested  in  mu- 
riatic acid,  they  become  transparent  and  flexible  like  leather,  the  earthy  matter  is 
dissolved,  and  after  the  acid  is  all  carefully  washed  away,  pieces  of  glue,  of  the 
same  shape  as  the  bones,  remain,  which  are  soluble  in  hot  water  and  adapted  to 
all  the  purposes  of  ordinary  glue,  without  further  preparation. 

Another  important  application  of  sulphuric  acid  may  be  adduced,  namely,  to  the 
refining  of  silver,  and  the  separation  of  gold,  which  is  always  present  in  some  pro- 
portion in  native  silver.  Silver,  as  it  is  usually  obtained  from  mines  in  Europe, 
contains,  in  sixteen  ounces,  six  to  eight  ounces  of  copper.  When  used  by  the 
silversmith,  or  in  coining,  sixteen  ounces  must  contain,  in  Germany  thirteen  ounces 
of  silver,  in  England  about  fourteen  and  a  half.  But  this  alloy  is  always  made 
artificially,  by  mixing  pure  silver  with  the  due  proportion  of  the  copper  ;  and  for 
this  purpose  the  silver  must  be  obtained  pure  by  the  refiner.  This  he  formerly 
effected  by  amalgamation,  or  by  roasting  it  with  lead  ;  and  the  cost  of  this  pro- 
cess was  about  21.  for  every  hundred  weight  of  silver.  In  the  silver  so  prepared, 
about  T^W^1  *°  ysWtn  Part  °f  g°ld  remained.  To  effect  the  separation  of  this  by 
nitric  hydrochloric  acid  was  more  expensive  than  the  value  of  the  gold ;  it  was, 
therefore,  left  in  utensils,  or  circulated  in  coin,  valueless.  The  copper,  too,  of  the 
native  silver  was  of  no  use  whatever.  But  the  T^utta  part  of  gold,  being  about 
one  and  one  half  per  cent,  of  the  value  of  the  silver,  now  covers  the  cost  of  refin- 
ing, and  affords  an  adequate  profit  to  the  refiner  ;  so  that  he  effects  the  separation 
of  the  copper,  and  returns  to  his  employer  the  whole  amount  of  the  pure  silver,  as 
well  as  the  copper,  without  demanding  any  payment :  he  is  amply  remunerated  by 
that  minute  portion  of  gold.  The  new  process  of  refining  is  a  most  beautiful  che- 
mical operation.  The  granulated  metal  is  boiled  in  concentrated  sulphuric  acid, 
which  dissolves  both  the  silver  and  the  copper,  leaving  the  gold  nearly  pure,  in  the 
form  of  a  black  powder.  The  solution  is  then  placed  in  a  leaden  vessel  containing 
metallic  copper ;  this  is  gradually  dissolved,  and  the  silver  precipitated  in  a  pure 
metallic  state.  The  sulphate  of  copper  is  also  a  valuable  product,  being  employed 
in  the  manufacture  of  green  and  blue  pigments. 

Other  immediate  results  of  the  economical  production  of  sulphuric  acid,  are  the 
general  employment  of  phosphorus  matches,  and  of  stearine  candles — that  beauti- 
ful substitute  for  tallow  and  wax.  Twenty-five  years  ago,  the  present  prices  and 
extensive  applications  of  sulphuric  and  muriatic  acids,  of  soda,  phosphorus,  &c., 
would  have  been  considered  utterly  impossible.  Who  is  able  to  foresee  what  new 
and  unthought-of  chemical  productions,  ministering  to  the  service  and  comforts  of 
mankind,  the  next  twenty-five  years  may  produce  ? 

After  these  remarks,  you  will  perceive  that  it  is  no  exaggeration  to  say,  we  may 
fairly  judge  of  the  commercial  prosperity  of  a  country  from  the  amount  of  sulphuric 
acid  it  consumes.  Reflecting  upon  the  important  influence  which  the  price  of  sul- 
phur exercises  upon  the  cost  of  production  of  bleached  and  printed  cotton  stuffs, 
soap,  glass,  &c.,  and  remembering  that  Great  Britain  supplies  America,  Spain, 
Portugal,  and  the  East,  with  these,  exchanging  them  for  raw  cotton,  silk,  wine, 
raisins,  indigo,  &c.,  &c.,  we  can  understand  why  the  English  Government  should 
have  resolved  to  resort  to  war  with  Naples,  in  order  to  abolish  the  sulphur  mo- 
nopoly, which  the  latter  power  attempted  recently  to  establish.  Nothing  could  be 
more  opposed  to  the  true  interests  of  Sicily  than  such  a  monopoly ;  indeed,  had  it 
been  maintained  a  few  years,  it  is  highly  probable  that  sulphur,  the  source  of  her 
wealth,  would  have  been  rendered  perfectly  valueless  to  her.  Science  and  industry 
form  a  power  to  which  it  is  dangerous  to  present  impediments.  It  was  not  difficult 
to  perceive  that  the  issue  would  be  the  entire  cessation  of  the  exportation  of  sul- 
phur from  Sicily.  In  the  short  period  the  sulphur  monopoly  lasted,  fifteen  patents 
were  taken  out  for  methods  to  obtain  back  the  sulphuric  acid  used  in  making  soda. 
Admitting  that  these  fifteen  experiments  were  not  perfectly  successful,  there  can  be 
no  doubt  it  would  ere  long  have  been  accomplished.  But  then,  in  gypsum  (sulphate 
of  lime),  and  in  heavy-spar  (sulphate  of  barytes),  we  possess  mountains  of  sulphu- 
ric acid?  in  galena  (sulphate  of  lead),  and  in  Iron  pyrites,  we  have  no  less  abun- 
dance of  sulphur.  The  problem  is,  how  to  separate  the  sulphuric  acid,  or  the  sul- 
phur, from  these  native  stores.  Hundreds  of  thousands  of  pounds  weight  of  sulphu- 
ric acid  were  prepared  from  iron  pyrites,  while  the  high  price  of  sulphur  consequent 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


upon  the  monopoly  lasted.  We  should  probably  ere  long  have  triumphed  over  all 
difficulties,  and  have  separated  it  from  gypsum.  The  impulse  has  been  given,  the 
possibility  of  the  process  proved,  and  it  may  happen  in  a  few  years  that  the  incon- 
siderate financial  speculation  of  Naples  may  deprive  her  of  that  lucrative  com- 
merce. In  like  manner,  Russia,  by  her  prohibitory  system,  has  lost  much  of  her 
trade  in  tallow  and  potash.  One  country  purchases  only  from  absolute  necessity 
from  another,  which  excludes  her  own  productions  from  her  markets.  Instead  of 
the  tallow  and  linseed  oil  of  Russia,  Great  Britain  now  uses  palm  oil  and  cocoa- 
nut  oil  of  other  countries.  Precisely  analogous  is  the  combination  of  workmen 
against  their  employers,  which  has  led  to  the  construction  of  many  admirable  ma- 
chines for  superseding  manual  labor.  In  commerce  and  industry  every  imprudence 
carries  with  it  its  own  punishment  ;  every  oppression  immediately  and  sensibly  re- 
coils upon  the  head  of  those  from  whom  it  emanates. 


LETTER  IV. 

MY  DEAR  SIR  : 

One  of  the  most  influential  causes  of  improvement  in  the  social  condition  of 
mankind,  is  that  spirit  of  enterprise  which  induces  men  of  capital  to  adopt  and 
carry  out  suggestions  for  the  improvement  of  machinery,  the  creation  of  new 
articles  of  commerce,  or  the  cheaper  production  of  those  already  in  demand  ; 
and  we  cannot  but  admire  the  energy  with  which  such  men  devote  their 
talents,  their  time,  and  their  wealth,  to  realize  the  benefits  of  the  discoveries  and 
inventions  of  science.  For  even  when  they  are  expended  upon  objects  wholly 
incapable  of  realization — nay,  even  when  the  idea  which  first  gave  the  impulse 
proves  in  the  end  to  be  altogether  impracticable  or  absurd,  immediate  good  to  the 
community  generally  ensues ;  some  useful  and  perhaps  unlocked  for  result  flows 
directly,  or  springs  ultimately,  from  exertions  frustrated  in  their  main  design. 
Thus  it  is  also  in  the  pursuit  of  science.  Theories  lead  to  experiments  and 
investigations ;  and  he  who  investigates  will  scarcely  ever  fail  of  being  rewarded 
by  discoveries.  It  may  be,  indeed,  the  theory  sought  to  be  established  is  entirely 
unfounded  in  nature;  but  while  searching  in  a  right  spirit  for  one  thing,  the 
inquirer  may  be  rewarded  by  finding  others  far  more  valuable  than  those  which 
he  sought. 

At  the  present  moment,  electro  magnetism,  as  a  moving  power,  is  engaging  great 
attention  and  study:  wonders  are  expected  from  its  application  to  this  purpose. 
According  to  the  sanguine  expectations  of  many  persons,  it  will  shortly  be  employed 
to  put  into  motion  every  kind  of  machinery,  and  among  other  things  it  will  be 
applied  to  impel  the  carriages  of  railroads,  and  this  at  so  small  a  cost,  that  expense 
will  no  longer  be  matters  of  consideration.  England  is  to  lose  her  superiority  as 
a  manufacturing  country,  inasmuch  as  her  vast  store  of  coals  will  no  longer  avail 
her  as  an  economical  source  of  motive  power.  "  We,"  say  the  German  cultivators 
of  this  science,  "  have  cheap  zinc,  and,  how  small  a  quantity  of  this  metal  is 
required  to  turn  a  lathe,  and  consequently  to  give  motion  to  any  kind  of 
machinery  !" 

Such  expectations  may  be  very  attractive,  and  yet  they  are  altogether  illusory ! 
they  will  not  bear  the  test  of  many  simple  calculations ;  and  this  our  friends  have 
not  troubled  themselves  to  institute. 

With  a  simple  flame  of  spirits  of  wine,  under  a  proper  vessel  containing  boiling 
water,  a  small  carriage  of  two  hundred  to  three  hundred  pounds  weight  can  be  put 
into  motion,  or  a  weight  of  eighty  to  one  hundred  pounds  may  be  raised  to  a  height 
of  twenty  feet.  The  same  effects  may  be  produced  by  dissolving  zinc  in  dilute  sul- 
phuric acid  in  a  certain  apparatus.  This  is  certainly  an  astonishing  and  highly 
interesting  discovery  ;  but  the  question  to  be  determined  is,  which  of  the  two 
processes  is  the  least  expensive  ? 

In  order  to  answer  this  question,  and  to  judge  correctly  of  the  hopes  entertained 
from  this  discovery,  let  me  remind  you  of  what  chemists  denominate  "equivalents." 
These  are  certain  unalterable  ratios  of  effects  which  are  proportionate  to  each 
other,  and  may  therefore  be  expressed  in  numbers.  Thus,  if  we  require  eight 
pounds  of  oxygen  to  produce  a  certain  effect,  and  we 'wish  to  employ  chlorine  for 
the  same  effect,  we  must  employ  neither  more  nor  less  than  thirty-five  and  a  half 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


pounds  weight.  In  the  same  manner,  six  pounds  weight  of  coal  are  equivalent  to 
thirty-two  pounds  weight  of  zinc.  The  numbers  representing  chemical  equivalents 
express  very  general  ratios  of  effects,  comprehending  for  all  bodies  all  the  actions 
they  are  capable  of  producing. 

If  zinc  be  combined  in  a  certain  manner  with  another  metal,  and  submitted  to 
the  action  of  dilute  sulphuric  acid,  it  is  dissolved  in  the  form  of  an  oxide  ;  it  is 
in  fact  burned  at  the  expense  of  the  oxygen  contained  in  fluid.  A  consequence 
of  this  action  is  the  production  of  an  electric  current,  which,  if  conducted  through 
a  wire,  renders  it  magnetic.  In  time  affecting  the  solution  of  a  pound  weight,  for 
example,  of  zinc,  we  obtain  a  definite  amount  of  force  adequate  to  raise  a  given 
weight  one  inch,  and  to  keep  it  suspended  ;  and  the  amount  of  weight  it  will  be 
capable  of  suspending  will  be  the  greater  the  more  rapidly  the  zinc  is  dissolved. 

By  alternately  interrupting  and  renewing  the  contact  of  the  zinc  with  the  acid, 
and  by  very  simple  mechanical  arrangements,  we  can  give  to  the  iron  an  upward 
and  downward  or  a  horizontal  motion,  thus  producing  the  conditions  essential  to 
the  motion  of  any  machinery. 

The  moving  force  is  produced  by  the  oxidation  of  the  zinc  ;  and,  setting  aside 
the  name  given  to  the  force  in  this  case,  we  know  that  it  can  be  produced  in  another 
manner.  If  we  burn  the  zinc  under  the  boiler  of  a  steam  engine,  consequently  in  the 
oxygen  of  the  air,  instead  of  the  galvanic  pile,  we  should  produce  steam,  and  by 
it  a  certain  amount  of  force.  If  we  should  assume  (which,  however,  is  not  proved), 
that  the  quantity  of  force  is  unequal  in  these  cases  —  that,  for  instance,  we  had 
obtained  double  or  triple  the  amount  in  the  galvanic  pile,  or  that  in  this  mode  of 
generating  force  less  loss  is  sustained  —  we  must  still  recollect  the  equivalents  of 
zinc  and  coal,  and  make  these  elements  of  our  calculation.  According  to  the 
experiments  of  Despretz,  six  pounds  weight  of  zinc,  in  combining  with  oxygen, 
develope  no  more  heat  than  one  pound  of  coal  ;  consequently,  under  equal  condi- 
tions, we  can  produce  six  times  the  amount  of  force  with  a  pound  of  coal  as  with  a 
pound  of  zinc.  It  is  therefore  obvious  that  it  would  be  more  advantageous  to 
employ  coal  instead  of  zinc,  even  if  the  latter  produced  four  times  as  much  force  in 
a  galvanic  pile,  as  an  equal  weight  of  coal  by  its  combustion  under  a  boiler. 
Indeed  it  is  highly  probable,  that  if  we  burn  under  the  boiler  of  a  steam  engine  the 
quantity  of  coal  required  for  smelting  the  zinc  from  its  ores,  we  shall  produce  far 
more  force  than  the  whole  of  the  zinc  so  obtained  could  originate  in  any  form  of 
apparatus  whatever. 

Heat,  electricity,  and  magnetism,  have  a  similar  relation  to  each  other  as  tho 
chemical  equivalents  of  coal,  zinc,  and  oxygen.  By  a  certain  measure  of  electricity 
we  produce  a  corresponding  proportion  of  heat  or  of  magnetic  power  ;  we  obtain 
that  electricity  by  chemical  affinity,  which  in  one  shape  produces  heat,  in  another 
electricity  or  magnetism.  A  certain  amount  of  affinity  produces  an  equivalent  of 
electricity  in  the  same  manner  as,  on  the  other  hand,  we  decompose  equivalents  of 
chemical  compounds  by  a  definite  measure  of  electricity.  The  magnetic  force  of  the 
pile  is  therefore  limited  to  the  extent  of  the  chemical  affinity,  and  in  the  case  before 
us  is  obtained  by  the  combination  of  the  zinc  aud  sulphuric  acid.  In  the  combus- 
tion of  coal,  the  heat  results  from,  and  is  measured  by,  the  affinity  of  the  oxygen 
of  the  atmosphere  for  that  substance. 

It  is  true  that,  with  a  very  small  expense  of  zinc,  we  can  make  an  iron  wire  a 
magnet  capable  of  sustaining  a  thousand  pounds  weight  of  iron  :  let  us  not  allow 
ourselves  to  be  misled  by  this.  Such  a  magnet  could  not  raise  a  single  pound 
weight  of  iron  two  inches,  and  therefore  could  not  impart  motion.  The  magnet 
acts  like  a  rock,  which,  while  at  rest,  presses  with  a  weight  of  a  thousand  pounds 
upon  a  basis  :  it  is  like  an  enclosed  lake,  without  an  outlet  and  without  a  fall.  But 
it  may  be  said,  we  have  by  mechanical  arrangements  given  it  an  outlet  and  a  fall. 
True  ;  and  this  must  be  regarded  as  a  great  triumph  of  mechanics  ;  and  I  believe  it  is 
susceptible  of  further  improvements,  by  which  greater  force  may  be  obtained.  But 
with  every  conceivable  advantage  of  mechanism,  no  one  will  dispute  that  one 
pound  of  coal,  under  the  boiler  of  a  steam  engine,  will  give  motion  to  a  mass 
several  hundred  times  greater  than  a  pound  of  zinc  in  the  galvanic  pile. 

Our  experience  of  the  employment  of  electro-magnetism  as  a  motory  power  is, 
however,  too  recent  to  enable  us  to  foresee  the  ultimate  results  of  contrivances  to 
apply  it  ;  and,  therefore,  those  who  have  devoted  themselves  to  solve  the  problem 
of  its  application  should  not  be  discouraged,  inasmuch  as  it  would  undoubtedly  be 
a  most  important  achievement  to  supersede  the  steam  engine,  and  thus  escape  the 
danger  of  railroads,  even  at  double  their  expense. 

Professor  Weber  of  Gottingen  has  thrown  out  a  suggestion,  that  if  a  contrivance 
could  be  devised  to  enable  us  to  convert  at  will  the  wheels  of  the  steam  carriage 


FAMILIAR  LETTERS  ON  CHEMISTRY.  15 

into  magnets,  we  should  be  enabled  to  ascend  and  descend  acclivities  with  great 
facility.  This  notion  may  ultimately  be,  to  a  certain  extent,  realized. 

The  employment  of  the  galvanic  pile  as  a  motory  power,  however,  must,  like 
every  other  contrivance,  depend  upon  the  question  of  its  relative  economy :  pro- 
bably some  time  hence  it  may  so  far  succeed  as  to  be  adopted  in  certain  favorable 
localities  ;  it  may  stand  in  the  same  relation  to  steam  power  as  the  manufacture  of 
beet  sugar  bears  to  that  of  cane,  or  as  the'  production  of  gas  from  oils  and  resins 
to  that  from  mineral  coal. 

The  history  of  beet-root  sugar  affords  us  an  excellent  illustration  of  the  'effect  of 
prices  upon  commercial  productions.  Tills  branch  of  industry  seems  at  length,  as 
to  its  processes,  to  be  perfected.  The  most  beautiful  white  sugar  is  now  manufac- 
tured from  the  beet-root,  in  the  place  of  the  treacle-like  sugar,  having  the  taste  of 
the  root,  which  was  first  obtained  ;  and  instead  of  3  or  4  per  cent*,  the  proportion 
obtained  by  Achard,  double  or  even  treble  that  amount  is  now  produced.  And 
notwithstanding  the  perfection  of  the  manufacture,  it  is  probable  it  will  ere  long  be 
in  most  places  entirely  discontinued.  In  the  years  1824  to  1827,  the  prices  of 
agricultural  produce  were  much  lower  than  at  present,  while  the  price  of  sugar  was 
the  same.  At  one  time  one  malter*  of  wheat  was  10s.,  and  one  klafterf  of  wood  18s., 
and  land  was  falling  in  price.  Thus,  food  and  fuel  were  cheap,  and  the  demand  for 
sugar  unlimited ;  it  was,  therefore,  advantageous  to  grow  beet-root,  and  to  dispose 
of  the  produce  of  land  as  sugar.  All  these  circumstances  are  now  different.  A  mal- 
ter  of  wheat  costs  18s.  ;  a  klafter  of  wood  30s.  to  36s.  Wages  have  risen,  but  not  in 
proportion,  while  the  price  of  colonial  sugar  has  fallen.  Within  the  limits  of  the 
German  commercial  league,  as  for  instance,  at  Frankfort-on-the-Maine,  a  pound  of 
the  whitest  and  best  loaf  sugar  is  Id. ;  the  import  duty  is  3fd.or  30s.  per  cwt.,  leav- 
ing 3|cZ.  as  the  price  of  the  sugar.  In  the  year,  1827,  then,  one  malter  of  wheat  was 
equal  to  forty  pounds  weight  of  sugar,  while  at  present  that  quantity  of  wheat  is 
worth  seventy  pounds  of  sugar.  If  indeed  fuel  were  the  same  in  price  as  formerly, 
and  seventy  pounds  of  sugar  could  be  obtained  from  the  same  quantity  of  the  root 
as  then  yielded  forty  pounds,  it  might  still  be  advantageously  produced  ;  but  the 
amount,  if  now  obtained  by  the  most  approved  methods  of  extraction,  falls  far 
short  of  this  :  and  as  fuel  is  double  the  price,  and  labor  dearer,  it  follows  that,  at 
present,  it  is  far  more  advantageous  to  cultivate  wheat  and  to  purchase  sugar. 

There  are,  however,  other  elements  which  must  enter  into  our  calculations;  but 
these  serve  to  confirm  our  conclusions,  that  the  manufacture  of  beet-root  sugar,  as  a 
commercial  speculation,  must  cease.  The  leaves  and  residue  of  the  root,  after  the 
juice  was  expressed,  were  used  as  food  for  cattle,  and  their  value  naturally 
increased  with  the  price  of  grain.  By  the  process  formerly  pursued,  seventy-five 
pounds  of  juice  were  obtained  from  one  hundred  pounds  of  beet-root,  and  gave 
five  pounds  of  sugar.  The  method  of  Schiitzenbach,  which  was  eagerly  adopted 
by  the  manufacturers,  produced  from  the  same  quantity  of  root  eight  pounds  of 
sugar  ;  but  it  was  attended  with  more  expense  to  produce,  and  the  loss  of  the 
residue  as  food  for  cattle.  The  increased  expense  in  this  process  arises  from  the 
larger  quantity  of  fuel  required  to  evaporate  the  water ;  for,  instead  of  merely 
evaporating  the  juice,  the  dry  residue  is  treated  with  water,  and  we  require  fuel 
sufficient  to  evaporate  one  hundred  and  six  pounds  of  fluid  instead  of  seventy- 
five  pounds,  and  the  residue  is  only  fit  for  manure.  The  additional  three  pounds 
of  sugar  are  purchased  at  the  expense  of  much  fuel,  and  the  loss  of  the  residue 
as  an  article  of  food. 

If  the  valley  of  the  Rhine  possessed  mines  of  diamonds,  as  rich  as  those  of  Gol- 
conda,  Visiapoor,  or  the  Brazils,  they  would  probably  not  be  worth  the  working : 
at  those  places  the  cost  of  extraction  is  28s.  to  30s.  the  carat.  With  us  it  amounts 
to  three  or  four  times  as  much — to  more,  in  fact,  than  diamonds  are  worth  in  the 
market.  The  sand  of  the  Rhine  contains  gold  ;  and  in  the  Grand  Duchy  of  Baden 
many  persons  are  occupied  in  gold  washing  when  wages  are  low ;  but  as  soon 
as  they  rise,  this  employment  ceases.  The  manufacture  of  sugar  from  beet-root, 
in  like  manner,  twelve  to  fourteen  years  ago,  offered  advantages  which  are  now 
lost :  instead,  therefore,  of  maintaining  it  at  a  great  sacrifice,  it  would  be  more 
reasonable,  more  in  accordance  with  true  natural  economy,  to  cultivate  other  and 
more  valuable  productions,  and  with  them  purchase  sugar.  Not  only  would  the 
state  be  a  gainer,  but  every  member  of  the  community.  This  argument  does  not 
apply,  perhaps,  to  France  and  Bohemia,  where  the  prices  of  fuel  and  of  colonial 
sugar  are  very  different  to  those  in  Germany. 

The  manufacture  of  gas  for  lighting,  from  coals,  resin,  and  oils,  stands  with  us 
on  the  same  barren  ground. 

*  Malter— a  measure  containing  several  bushels,. but  varying  in  different  countries, 
f  Klafter— a  cord,  a  stack,  measuring  six  feet  every  way. 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


The  materials  from  which  gas  is  manufactured  in  England  bears  a  direct  pro- 
portion to  the  price  of  corn  ;  there  the  prices  of  tallow  and  oil  are  twice  as  great 
as  in  Germany,  but  iron  and  coal  are  two  thirds  cheaper  ;  and  even  in  England  the 
manufacture  of  gas  is  only  advantageous  when  the  other  products  of  the  distillation 
of  coal,  the  coke,  &c.,  can  be  sold. 

It  would  certainly  be  esteemed  one  of  the  greatest  discoveries  of  the  age  if  any 
one  could  succeed  in  condensing  coal  gas  into  a  white,  dry,  solid,  odorless  sub- 
stance, portable,  and  capable  of  being  placed  upon  a  candlestick,  and  burned  in  a 
lamp.  Wax,  tallow,  and  oil,  are  combustible  gases  in  a  solid  or  fluid  form,  which 
offer  many  advantages  for  lighting,  not  performed  by  gas  :  they  furnish,  in  well- 
constructed  lamps,  as  much  light,  without  requiring  the  expensive  apparatus 
necessary  for  the  combustion  of  gas,  and  they  are  generally  more  economical.  In 
large  towns,  or  such  establishments  as  hotels,  where  coke  is  in  demand,  and  where 
losses  in  stolen  tallow  or  oil  must  be  considered,  together  with  the  labor  in  snuffing 
candles  and  cleaning  lamps,  the  higher  price  of  gas  is  compensated.  In  places 
where  gas  can  be  manufactured  from  resin,  oil  of  turpentine,  and  other  cheap  oil, 
as  at  Frankfort,  this  is  advantageous  so  long  as  it  is  pursued  on  a  small  scale  only. 
If  large  towns  were  lighted  in  the  same  manner,  the  materials  would  rise  in  price  : 
the  whole  amount  at  present  produced  would  scarcely  suffice  for  two  such  towns  as 
Berlin  and  Munich.  But  no  just  calculation  can  be  made  from  the  present  prices 
of  turpentine,  resin,  &c.,  which  are  not  produced  upon  any  large  scale. 


LETTER  V. 

MY  DEAR  SIR  : 

Until  very  recently  it  was  supposed  that  the  physical  qualities  of  bodies,. that 
is,  hardness,  color,  density,  transparency,  &c.,  and  still  more  their  chemical  pro- 
perties, must  depend  upon  the  nature  of  their  elements,  or  upon  their  composition. 
It  was  tacitly  received  as  a  principle,  that  two  bodies  containing  the  same  elements 
in  the  same  proportion,  must  of  necessity  possess  the  same  properties.  We  could 
not  imagine  an  exact  identity  of  composition,  giving  rise  to  two  bodies  entirely 
different  in  their  sensible  appearance  and  chemical  relations.  The  most  ingenious 
philosophers  entertained  the  opinion  that  chemical  combination  is  an  inter-penetra- 
tion of  the  particles  of  different  kinds  of  matter,  and  that  all  matter  is  susceptible 
of  infinite  division.  This  has  proved  to  be  altogether  a  mistake.  If  matter  were 
infinitely  divisible  in  this  sense,  its  particles  must  be  imponderable,  and  a  million 
of  such  molecules  could  not  weigh  more  than  an  infinitely  small  one.  But  the 
particles  of  that  imponderable  matter,  which,  striking  upon  the  retina,  gives  us  the 
sensation  of  light,  are  not  in  a  mathematical  sense  infinitely  small. 

Inter-penetration  of  elements  in  the  production  of  a  chemical  compound,  sup- 
poses two  distinct  bodies,  A  and  B,  to  occupy  one  and  the  same  space  at  the  same 
time.  If  this  were  so,  different  properties  could  not  exist  with  an  equal  and 
identical  composition. 

That  hypothesis,  however,  has  shared  the  fate  of  innumerable  imaginative 
explanations  of  natural  phenomena,  in  which  our  predecessors  indulged.  They 
have  now  no  advocate.  The  force  of  truth  dependent  upon  observation  is  irresis- 
tible. A  great  many  substances  have  been  discovered  among  organic  bodies, 
composed  of  the  same  elements  in  the  same  relative  proportions,  and  yet  exhibiting 
physical  and  chemical  properties  perfectly  distinct  one  from  another.  To  such 
substances  the  term  Isomeric  (from  KJOJ  equal  and  ^ poj  part]  is  applied.  A  great 
class  of  bodies,  known  as  the  volatile  oils,  oils  of  turpentine,  essence  of  lemons, 
oil  of  balsam,  of  copaiba,  oil  of  rosemary,  oil  of  juniper,  and  many  others,  differing 
widely  from  each  other  in  their  odor,  in  their  medicinal  effects,  in  their  boiling 
point,  in  their  specific  gravity,  &c.,  are  exactly  identical  in  composition, — they 
contain  the  same  elements,  carbon  and  hydrogen,  in  the  same  proportions. 

How  admirably  simple  does  the  chemistry  of  organic  nature  present  itself  to  us 
from  this  point  of  view.  An  extraordinary  variety  of  compound  bodies  produced 
with  equal  weights  of  two  elements !  and  how  wide  their  dissimilarity  !  The 
crystallised  part  of  the  oil  of  roses,  the  delicious  fragrancy  of  which  is  so  well 
known,  a  solid  at  ordinary  temperatures,  although  readily  volatile,  is  a  compound 
body  containing  exactly  the  same  elements,  and  in  the  same  proportion,  as  the  gas 


FAMILIAR  LETTERS  ON  CHEMISTRY.  17 

we  employ  for  lighting  our  streets ;  and,  in  short,  the  same  elements,  in  the  same 
relative  quantities,  are  found  in  a  dozen  other  compounds,  all  differing  essentially 
in  their  physical  and  chemical  properties. 

These  remarkable  truths,  so  highly  important  in  their  applications,  were  not 
received  and  admitted  as  sufficiently  established,  without  abundant  proofs.  Many 
examples  have  long  been  known  where  the  analysis  of  two  different  bodies  gave 
the  same  composition  ;  but  such  cases  were  regarded  as  doubtful :  at  any  rate, 
they  were  isolated  observations,  homeless  in  the  realms  of  science,  until,  at  length, 
examples  were  discovered  of  two  or  more  bodies,  whose  absolute  identity  of  com- 
position, with  totally  distinct  properties,  could  be  demonstrated  in  a  more  obvious 
and  conclusive  manner  than  by  mere  analysis ;  that  is,  they  can  be  converted  and 
reconverted  into  each  other  without  addition  and  without  subtraction. 

In  cyanuric  acid,  hydrated  cyanic  acid,  and  cyamelide,  we  have  three  such 
isomeric  compounds. 

Cyanuric  acid  is  crystalline,  soluble  in  water  and  capable  of  forming  salts  with 
metallic  oxides. 

Hydrated  cyanic  acid  is  a  volatile  and  highly  blistering  fluid,  which  cannot  be 
brought  into  contact  with  water,  without  being  instantaneously  decomposed. 

Cyamelide  is  a  white  substance  very  like  porcelain,  absolutely  insoluble  in 
water. 

Now,  if  we  place  the  first, — cyanuric  acid,— in  a  vessel  hermetically  sealed,  and 
apply  a  high  degree  of  heat,  it  is  converted  by  its  influence  into  hydratic  cyanic 
acid ;  and,  then,  if  this  is  kept  for  some  time  at  the  common  temperature,  it  passes 
into  cyamelide,  no  other  element  being  present.  And  again  inversely,  cyamelide 
can  be  converted  into  cyanuric  acid  and  hydrated  cyanic  acid. 

We  have  three  other  bodies  which  pass  through  similar  changes,  in  aldehyde, 
metaldehyde,  and  eltaldehyde  ;  and,  again  two,  in  urea  and  cyanuret  of  ammonia. 
Further,  one  hundred  parts  of  aldehyde  hydrated  butyric  acid  and  acetic  ether 
contain  the  same  elements  in  the  same  proportion.  Tnus  one  substance  may  be 
converted  into  another  without  addition  or  subtraction,  and  without  the  partici- 
pation of  any  foreign  bodies  in  the  change. 

The  doctrine  that  matter  is  npt  infinitely  divisible,  but  on  the  contrary,  consists 
of  atoms  incapable  of  further  division,  alone  furnishes  us  with  a  satisfactory  ex- 
planation of  these  phenomena.  In  chemical  combinations,  the  ultimate  atoms  of 
bodies  do  ndt  penetrate  each  other,  they  are  only  arranged  side  by  side  in  a  certain 
order,  and  the  properties  of  the  compound  depend  entirely  upon  this  order.  If 
they  are  made  to  change  their  place — their  mode  of  arrangement — by  an  impulse 
from  without,  they  combine  again  in  a  different  manner,  and  another  compound  is 
formed  with  totally  different  properties.  We  may  suppose  that  one  atom  combines 
with  one  atom  of  another  element  to  form  a  compound  atom,  while  in  other  bodies, 
two  and  two,  four  and  four,  eight  and  eight,  are  united  ;  so  that  in  all  such  com- 
pounds the  amount  per  cent,  of  the  elements  is  absolutely  equal ;  and  yet  their 
physical  and  chemical  properties  must  be  totally  different,  the  constitution  of  each 
atom  being  peculiar,  in  one  body  consisting  of  two,  in  another  of  four,  in  the  third 
of  eight,  and  in  a  fourth  of  sixteen  simple  atoms. 

The  discovery  of  these  facts  immediately  led  to  many  most  beautiful  and  inter- 
esting results  ;  they  furnished  us  with  a  satisfactory  explanation  of  observations 
which  were  before  veiled  in  mystery — a  key  to  many  of  nature's  most  curious 
recesses. 

Again,  solid  bodies,  whether  simple  or  compound,  are  capable  of  existing  in  two 
states,  which  are  known  by  the  terms  amorphous  and  crystalline. 

When  matter  is  passing  from  a  gaseous  or  liquid  state  slowly  into  a  solid,  an 
incessant  motion  is  observed,  as  if  the  molecules  were  minute  magnets :  they  are 
seen  to  repel  each  other  in  one  direction,  and  to  attract  and  cohere  together  in 
another  and  in  the  end  become  arranged  into  a  regular  form,  which,  under  equal 
circumstances,  is  always  the  same  for  any  given  kind  of  matter  :  that  is,  crystals  are 
formed. 

Time  and  freedom  of  motion  for  the  particles  of  bodies  are  necessary  to  the 
formation  of  crystals.  If  we  force  a  fluid  or  a  gas  to  become  suddenly  solid, 
leaving  no  time  for  its  particles  to  arrange  themselves,  and  cohere  in  that  direction 
in  which  the  cohesive  attraction  is  strongest,  no  crystals  will  be  formed,  but  the 
resulting  solid  will  have  a  different  color,  a  different  degree  of  hardness  and 
cohesion,  and  will  retract  light  differently ;  in  one  word,  will  be  amorphous.  Thus 
we  have  cinnabar  as  a  red  and  a  jet-black  substance;  sulphur  a  fixed  and  brittle 
body,  and  soft,  semi-transparent  and  ductile  ;  glass  as  a  milk-white  opaque  sub- 
stance, so  hard  that  it  strikes  fire  with  steel,  and  in  its  ordinary  and  well-known 
state.  These  dissimilar  states  and  properties  of  the  same  body  are  occasioned  in 

2 


Jg  FAMILIAR  LETTERS  ON  CHEMISTRY. 

one  case  by  a  regular,  in  the  other  by  an  irregular  arrangement  of  its  atoms:  one 
is  crystalline,  the  other  amorphous. 

Applying  these  facts  to  natural  productions,  we  have  reason  to  believe  that  clay- 
elate  and  many  kinds  of  greywacke  are  amorphous  feldspar,  as  transition  limestone 
is  amorphous  marble,  basalt  and  lava  mixtures  of  amorphous  zeolite  and  augite. 
Any  thing  that  influences  the  cohesion,  must  also  in  a  certain  degree  alter  the  pro- 
perties of  bodies.  Carbonate  of  lime,  if  crystallized  at  ordinary  temperatures, 
possesses  the  crystalline  form,  hardness,  and  refracting  power  of  common  spar  ;  if 
crystallized  at  a  higher  temperature,  it  has  the  form  and  properties  of  arragonite. 

Finally.  Isomorphism,  or  the  equality  of  form  of  many  chemical  compounds  having 
a  different  composition,  tends  to  prove  that  matter  consists  of  atoms  the  mere 
arrangement  of  which  produces  all  the  properties  of  bodies.  But  when  we  find 
that  a  different  arrangement  of  the  same  elements  gives  rise  to  various  physicial  and 
chemical  properties,  and  a  similar  arrangement  of  different  elements  produces 
properties  very  much  the  same,  may  we  not  inquire  whether  some  of  those  bodies 
which  we  regard  as  elements  may  not  be  merely  modifications  of  the  same  sub- 
stance ?  whether  they  are  not  the  same  matter  in  a  different  state  of  arrangement  ? 
We  know,  in  fact,  the  existence  of  iron  in  two  states,  so  dissimilar,  that  in  the  one, 
it  is  to  the  electric  chain  like  platinum,  and  in  the  other  it  is  like  zinc ;  so  that 
powerful  galvanic  machines  have  been  constructed  of  this  one  metal. 

Among  the  elements  are  several  instances  of  remarkable  similarity  of  properties. 
Thus  there  is  a  strong  resemblance  between  platinum  and  iridium  ;  bromine  and 
iodine ;  iron,  manganese  and  magnesium  ;  cobalt  and  nickel,  phosphorus  and 
arsenic ;  but  this  resemblance  consists  mainly  in  their  forming  isomorphous  com- 
pounds in  which  these  elements  exist  in  the  same  relative  proportion.  These  com- 
pounds are  similar,  because  the  atoms  of  which  they  are  composed  are  arranged  in 
the  same  manner.  The  converse  of  this  is  also  true :  nitrate  of  stroutia  becomes 
quite  dissimilar  to  its  common  state  if  a  certain  proportion  of  water  is  taken  into 
its  composition. 

If  we  suppose  selenium  to  be  merely  modified  sulphur  and  phosphorus,  modified 
arsenic,  how  does  it  happen,  we  must  inquire,  that  sulphuric  acid  and  selenic  acid, 
phosphoric  and  arsenic  acid,  respectively  form  compounds  which  it  is  impossible  to 
distinguish  by  their  form  and  solubility  ?  Were  these  merely  isomeric  they  ought 
to  exhibit  properties  quite  dissimilar ! 

We  have  not,  I  believe,  at  present  the  remotest  ground  to  suppose  that  any  one  of 
those  substances  which  chemists  regard  as  elements,  can  be  converted  into 
another.  Such  a  conversion,  indeed,  would  presuppose  that  the  element  was  com- 
posed of  two  or  more  ingredients,  and  was,  in  fact,  not  an  element ;  and  until  the 
decomposition  of  these  bodies  is  accomplished,  and  their  constituents  discovered, 
all  pretensions  to  such  conversions  deserve  no  notice. 

Mr.  Brown,  of  Edinburgh,  thought  he  had  converted  iron  into  rhodium,  and 
carbon  or  paracyanogen  into  silicon.  His  paper  upon  this  subject  was  published 
in  the  Transactions  of  the  Royal  Society  of  Edinburgh,  and  contained  internal 
evidence,  without  a  repitition  of  his  experiments,  that  he  was  totally  unacquainted 
with  the  principles  of  chemical  analysis.  But  his  experiments  have  been  carefully 
repeated  by  qualified  persons,  and  they  have  completely  proved  his  ignorance  j  his 
rhodium  is  iron,  and  his  silicon  an  impure  incombustible  coal. 


LETTER 

MY  DEAR  SIR  : 

One  of  the  most  remarkable  effects  of  the  recent  progress  of  science  is  the 
alliance  of  chemistry  with  physiology,  by  which  a  new  and  unexpected  light  has 
been^thrown  upon  the  vital  processes  of  plants  and  animals.  We  have  now  no 
longer  any  difficulty  in  understanding  the  different  actions  of  aliments,  poisons, 
and  remedial  agents — we  have  a  clear  conception  of  the  causes  of  hunger,  of  the 
exact  nature  of  death  ;  and  we  are  not,  as  formerly,  obliged  to  content  ourselves 
with  a  mere  description  of  their  symptoms.  It  is  now  ascertained  with  positive 
certainty,  that  all  the  substances  which  constitute  the  food  of  man  must  be  divided 
into  two  great  classes,  one  of  w^ich  serves  for  the  nitrition  and  reproduction  of  the 
animal  body,  while  the  other^  Ministers  to  quite  different  purposes.  Thus  starch, 


FAMILIAR  LETTERS  ON  CHEMISTRY.  19 

gum,  sugar,  beer,  wine,  spirits,  &c.,  furnish  no  element  capable  of  entering  into 
the  composition  of  blood,  muscular  fibre,  or  any  part  which  is  the  seat  of  the  vital 
principle.  It  must  surely  be  universally  interesting  to  trace  the  great  change  our 
views  have  undergone  upon  these  subjects,  as  well  as  to  become  acquainted  with 
the  researches  from  which  our  present  knowledge  is  derived. 

The  primary  conditions  of  the  maintenance  of  animal  life,  are  a  constant  supply 
of  certain  matters,  animal  food,  and  of  oxygen,  in  the  shape  of  atmospheric  air. 
During  every  moment  of  life,  oxygen  is  absorbed  from  the  atmosphere  in  the  organs 
of  respiration,  and  the  act  of  breathing  cannot  cease  while  life  continues. 

The  observations  of  physiologists  have  demonstrated  that  the  body  of  an  adult 
man  supplied  abundantly  with  food,  neither  increases  nor  diminishes  in  weight 
during  twenty-four  hours,  and  yet  the  quantity  of  oxygen  absorbed  into  his  system^  t/ 
in  that  period,  is  very  considerable.  According  to  the  experiments  of  Lavoisiert  ' 
an  adult  man  takes  into  his  system  from  the  atmosphere,  in  one  year,  no  less  than 
seven  hundred  and  forty-six  pounds  weight  of  oxygen ;  the  calculations  of  Men- 
zies  make  the  quantity  amount  even  to  eight  hundred  and  thirty-seven  pounds  ; 
but  we  find  his  weight  at  the  end  of  the  year  either  exactly  the  same,  or  differing 
one  way  or  other  by  at  most  a  few  pounds.  What,  it  may  be  asked,  has  become 
of  the  enormous  amount  of  oxygen  thus  introduced  into  the  human  system  in  the 
course  of  one  year  ?  We  can  answer  this  question  satisfactorily.  No  part  of  the 
oxygen  remains  in  the  body,  but  is  given  out  again,  combined  with  carbon  and  hy- 
drogen. The  carbon  and  hydrogen  of  certain  parts  of  the  animal  body  combine 
with  the  oxygen  introduced  through  the  lungs  and  skin,  and  pass  off  in  the  forms 
of  carbonic  acid  and  vapor  of  water.  At  every  expiration  and  every  moment  of 
life,  a  certain  amount  of  its  elements  are  separated  from  the  animal  organism, 
having  entered  into  combination  with  the  oxygen  of  the  atmosphere. 

In  order  to  obtain  a  basis  for  an  approximate  calculation,  we  may  assume,  with 
Lavoisier  and  Seguin,  that  an  adult  man  absorbs  into  his  system  32£  ounces  of 
oxygen  daily — that  is,  46,037  cubic  inches  =  15,661  grains,  French  weight ;  and 
further,  that  the  weight  of  the  whole  mass  of  his  blood  is  twenty-four  pounds,  of 
which  eighty  per  cent,  is  water.     Now,  from  the  known  composition  of  the  blood, 
we  know  that  in  order  to  convert  its  whole  amount  of  carbon  and  hydrogen  into 
carbonic  acid  and  water  64.102  grains  of  oxygen  are  required.      This  quantity  will 
be  taken  into  the  system  in  four  days  and  five  hours.     Whether  the  oxygen  enters 
into  combination  directly  with  the  elements  of  the  blood,  or  with  the  carbon  and^ 
hydrogen  of  other  parts  of  the  body,  it  follows  inevitably — the  weight  of  the  body  1 
remajjiing^uncha^ed,  and  in  a^ normal^  condition — that  as  much  of  these  elements  \ 
as  will  suffice  to  supply  t we nty-iou r ~"p~oun ds  of  blood,  must  be  taken  into  the  ! 
system  in  four  days  and  five  hours  ;  and  this  necessary  amount  is  furnished  by  ! 
the  food. 

We  have  not,  however,  remained  satisfied  with  mere  approximation :  we  have 
determined  accurately,  in  certain  cases,  the  quantity  of  carbon  taken  daily  in  the 
food,  and  of  that  which  passes  out  of  the  body  in  the  faeces  and  urine  combined — 
that  is,  uncombined  with  oxygen;  and  from  these  investigations  it  appears  that  an 
adult  man,  taking  moderate  exercise,  consumes  13.910  ounces  of  carbon,  which  pass 
off  through  the  skin  and  lungs  as  carbonic  acid  gas.* 

It  requires  thirty-seven  ounces  of  oxygen  to  convert  13.910  of  carbon  into  carbonic 
acid.  Again :  according  to  the  analysis  of  Boussingault  (Annales  de  Chim.  et  de 
Phys.  Ixx.  i.,  p.  136,)  a  horse  consumes  79.110  ounces  of  carbon  in  twenty-four 
hours,  a  milch  cow  70|  ounces ;  so  that  the  horse  requires  13  pounds  3i  ounces,  and 
the  cow  11  pounds  10J  ounces  of  oxygen. f 

As  no  part  of  the  oxygen  taken  into  the  system  of  an  animal  is  given  off  in  any 
other  form  than  combined  with  carbon  or  hydrogen,  and  as  in  a  normal  condition, 
or  state  of  health,  the  carbon  and  hydrogen  so  given  off,  are  replaced  by  those 
elements  in  the  food,  it  is  evident  that  the  amount  of  nourishment  required  by  an 
animal  for  its  support,  must  be  in  a  direct  ratio  with  the  quantity  of  oxygen  taken  into 
its  system.  Two  animals,  which  in  equal  times  take  up  by  means  of  the  lungs  and  skin 
unequal  quantities  of  oxygen,  consume  an  amount  of  food  unequal  in  the  same  ratio. 
The  consumption  of  oxygen  in  a  given  time  may  be  expressed  by  the  number  of 

*  This  account  is  deduced  from  observations  made  upon  the  average  daily  consumption  of 
about  thirty  soldiers  in  barracks.  The  food  of  these  men,  consisting  of  meat,  bread,  potatoes, 
lentiles,  peas,  beans,  butter,  salt,  pepper,  &c.,  was  accurately  weighed  during  a  month,  and 
each  article  subjected  to  ultimate  analysis.  Of  the  quantity  of  food,  beer,  and  spirits,  taken 
by  the  men  when  out  of  barracks,  we  have  a  close  approximation  from  the  report  of  the 
sergeant ;  and  from  the  weight  and  analysis  of  the  faeces  and  urine,  it  appears  that  the  carbon 
which  passe*  off  through  these  channels  may  be  considered  equivalent  to  the  amount  taken 
in  that  portion  of  the  food,  and  of  sour-crout,  which  was  not  included  in  the  estimate. 
f!6  ounces=i  kilogramme. 


20  FAMILIAR  LETTERS  ON  CHEMISTRY. 

respirations ;  it  is,  therefore,  obvious,  that  in  the  same  animal  the  quantity  of 
nourishment  required  must  vary  with  the  force  and  number  of  respirations.  A 
child  breathes  quicker  than  an  adult,  and,  consequently,  requires  food  more  fre- 
quently, and  proportionably  in  larger  quantity,  and  bears  hunger  less  easily.  A 
bird,  deprived  of  food,  dies  on  the  third  day,  while  a  serpent,  confined  under  a  bell, 
respires  so  slowly,  that  the  quantity  of  carbonic  acid  generated  in  an  hour  can 
scarcely  be  observed,  and  it  will  live  three  months,  or  longer,  without  food.  The 
number  of  respirations  is  fewer  in  a  state  of  rest  than  during  labor  or  exercise ;  the 
quantity  of  food  necessary  in  both  cases  must  be  in  the  same  ratio.  An  excess  of 
food,  a  want  of  a  due  amount  of  respired  oxygen,  or  of  exercise,  as  also  of  great 
exercise,  (which  obliges  us  to  take  an  increased  supply  of  food,)  together  with  weak 
organs  of 'digestion,  are  incompatible  with  health. 

But  the  quantity  of  oxygen  received  by  an  animal  through  the  lungs,  not  only 
depends  upon  the  number  of  respirations,  but  also  upon  the  temperature  of  the 
respired  air.  The  size  of  the  thorax  of  an  animal  is  unchangeable  ;  we  may,  there- 
fore, regard  the  volume  of  air  which  enters  at  every  inspiration  as  uniform.  But  its 
weight,  and  consequently  the  amount  of  oxygen  it  contains,  is  not  constant.  Air  is 
expanded  by  heat,  and  contracted  by  cold — an  equal  volume  of  hot  and  cold  air 
contains,  therefore,  an  unequal  amount  of  oxygen.  In  summer,  atmospheric  air 
contains  water  in  the  form  of  vapor ;  it  is  nearly  deprived  of  it  in  winter.  The 
volume  of  oxygen  in  the  same  volume  of  air  is  smaller  in  summer  than  in  winter. 
In  summer  and  winter,  at  the  pole  and  at  the  equator,  we  inspire  an  equal  volume 
of  air ;  the  cold  air  is  warmed  during  respiration,  and  acquires  the  temperature  of 
the  body.  In  order,  therefore,  to  introduce  into  the  lungs  a  given  amount  of  oxygen, 
less  expenditure  of  force  is  necessary  in  winter  than  in  summer,  and  for  the  same 
expenditure  of  force  more  oxygen  is  inspired  in  winter.  It  is  also  obvious  that,  in 
an  equal  number  of  respirations,  we  consume  more  oxygen  at  the  level  of  the  sea 
than  on  a  mountain. 

The  oxygen,  taken  into  the  system,  is  given  out  again  in  the  same  form,  both  in 
summer  and  winter;  we  expire  more  carbon  at  a  low  than  at  a  high  temperature, 
and  require  more  or  less  carbon  in  our  food  in  the  same  proportion ;  and  conse- 
quently more  is  respired  in  Sweden  than  in  Sicily,  and  in  our  own  country  an 
eighth  more  in  winter  than  in  summer.  Even  if  an  equal  weight  of  food  is  con- 
sumed in  hot  and  cold  climates,  Infinite  Wisdom  has  ordained  that  very  unequal 
proportions  of  carbon  shall  be  taken  in  it.  The  food  prepared  for  the  inhabitants 
of  southern  climes  does  not  contain  in  a  fresh  state  more  than  twelve  per  cent,  of 
carbon,  while  the  blubber  and  train,  oil,  which  feed  the  inhabitants  of  polar  regions, 
contain  sixty-six  fco  eighty  per  cent  of  that  element. 

From  the  same  cause  it  is  comparatively  easy  to  be  temperate  in  warm  climates, 
or  to  bear  hunger  for  a  long  time  under  the  equator;  but  cold  and  hunger  united 
very  soon  produce  exhaustion. 

The  oxygen  of  the  atmosphere  received  into  the  blood  in  the  lungs,  and  circulated 
throughout  every  part  of  the  animal  body,  acting  upon  the  elements  of  the  food,  is 
the  source  of  animal  heat. 


LETTER  VII. 

MY  DEAR  SIR: 

The  source  of  animal  heat,  its  laws,  and  the  influence  it  exerts  upon  the 
functions  of  the  animal  body,  constitute  a  curious  and  highly  interesting  subject,  to 
which  I  would  now  direct  your  attention. 

All  living  creatures,  whose  existence  depends  upon  the  absorption  of  oxygen, 
possess  within  themselves  a  source  of  heat,  independent  of  surrounding  objects. 

This  general  truth  applies  to  all  animals,  and  extends  to  the  seed  of  plants  in 
the  act  of  germination,  to  flower-buds  when  developing,  and  fruits  during  their 
maturation. 

In  the  animal  body,  heat  is  produced  only  in  those  parts  to  which  arterial  blood, 
and  with  it  the  oxygen  absorbed  in  respiration,  is  conveyed.  Hair,  wool,  and 
feathers,  receive  no  arterial  blood,  and  therefore,  in  them  no  heat  is  developed.  The 
combination  of  a  combustible  substance  with  oxygen  is,  under  all  circumstances,  the 
only  source  of  animal  heat.  In  whatever  way  carbon  may  combine  with  oxygen, 


FAMILIAR  LETTERS  ON  CHEMISTRY.  21 

the  act  of  combination  is  accompanied  by  the  disengagement  of  heat.  It  is  indif- 
ferent whether  this  combination  takes  place  rapidly  or  slowly,  at  a  high  or  at  a  low 
temperature ;  the  amount  of  heat  liberated  is  a  constant  quantity. 

The  carbon  of  the  food  being  converted  into  carbonic  acid  within  the  body,  must 
give  out  exactly  as  much  heat  as  if  it  had  been  directly  burnt  in  oxygen  gas,  or  in 
common  air;  the  only  difference  is,  the  production  of  the  heat  is  diffused  over  unequal 
times.  In  oxygen  gas  the  combustion  of  carbon  is  rapid,  and  the  heat  intense ;  in 
atmospheric  air  it  burns  slower,  and  for  a  longer  time,  the  temperature  being 
lower ;  in  the  animal  body  the  combination  is  still  more  gradual,  and  the  heat  is 
lower  in  proportion. 

It  is  obvious  that  the  amount  of  heat  liberated  must  increase  or  diminish  with 
the  quantity  of  oxygen  introduced  in  equal  times  by  respiration.  Those  animals, 
therefore,  which  respire  frequently,  and  consequently  consume  much  oxygen,  pos- 
sess a  higher  temperature  than  others,  which,  with  a  body  of  equal  size  to  be  heated, 
take  into  the  system  less  oxygen.  The  temperature  of  a  child  (102°)  is  higher  than 
that  of  an  adult  (99.5°).  That  of  birds  (104°  to  105.4°),  is  higher  than  that  of  qua- 
drupeds (98.5°  to  100.4°),  or  that  of  fishes,  or  amphibia,  whose  proper  temperature, 
is  from  2.7°  to  3.6°  higher  than  that  of  the  medium  in  which  they  live.  All 
animals,  strictly  speaking,  are  warm-blooded ;  but  in  those  only  which  possess 
lungs  is  the  temperature  of  the  body  quite  independent  of  the  surrounding  medium. 

The  most  trustworthy  observations  prove  that  in  all  climates,  in  the  temperate 
zones,  as  well  as  at  the  equator  or  the  poles,  the  temperature  of  the  body  in  man, 
and  in  what  are  commonly  called  warm-blooded  animals,  is  invariably  the  same ; 
yet  how  different  are  the  circumstances  under  which  they  live ! 

The  animal  body  is  a  heated  mass,  which  bears  the  same  relations  to  surrounding 
objects  as  any  other  heated  mass.  It  receives  heat  when  the  surrounding  objects 
are  hotter,  it  loses  heat  when  they  are  colder  than  itself. 

We  know  that  the  rapidity  of  cooling  increases  with  the  difference  between  the 
temperature  of  the  heated  body  and  that  of  the  surrounding  medium ;  that  is,  the 
colder  the  surrounding  medium  the  shorter  the  time  required  for  the  cooling  of  the 
heated  body. 

How  unequal,  then,  must  be  the  loss  of  heat  in  a  man  at  Palermo,  where  the 
external  temperature  is  nearly  equal  to  that  of  the  body,  and  in  the  polar  regions, 
where  the  external  temperature  is  from  seventy  to  ninety  degrees  lower  ! 

Yet,  notwithstanding  this  extremely  unequal  loss  of  heat,  experience  has  shown 
that  the  blood  of  the  inhabitant  of  the  arctic  circle  has  a  temperature  as  high  as 
that  of  the  native  of  the  south,  who  lives  in  so  different  a  medium. 

This  fact,  when  its  true  significance  is  perceived,  proves  that  the  heat  given  off 
to  the  surrounding  medium  is  restored  within  the  body  with  great  rapidity.  This 
compensation  must,  consequently,  take  place  more  rapidly  in  winter  than  in  sum- 
mer, at  the  pole  than  at  the  equator. 

Now,  in  different  climates  the  quantity  of  oxygen  introduced  into  the  system  by 
respiration,  as  has  been  already  shown,  varies  according  to  the  temperature  of  the 
external  air;  the  quantity  of  inspired  oxygen  increases  with  the  loss  of  heat  by 
external  cooling;  and  the  quantity  of  carbon  or  hydrogen  necessary  to  combine 
with  this  oxygen  must  be  increased  in  the  same  ratio. 

It  is  evident  that  the  supply  of  the  heat  lost  by  cooling  is  effected  by  the  mutual 
action  of  the  elements  of  the  food  and  the  inspired  oxygen,  which  combine  together. 
To  make  use  of  a  familiar,  but  not  on  that  account  a  less  just  illustration,  the  ani- 
mal body  acts,  in  this  respect,  as  a  furnace,  which  we  supply  with  fuel.  It  signifies 
nothing  what  intermediate  forms  food  may  assume,  what  changes  it  may  undergo  in 
the  body,  the  last  change  is  uniformly  the  conversion  of  its  carbon  into  carbonic 
acid,  and  of  its  hydrogen  into  water.  The  unassimilated  nitrogen  of  the  food, 
along  with  the  unburned  or  unoxidized  carbon,  is  expelled  in  the  urine  or  in  the 
solid  excrements.  In  order  to  keep  up  in  the  furnace  a  constant  temperature,  we 
must  vary  the  supply  of  fuel  according  to  the  external  temperature,  that  is,  accord- 
ing to  the  supply  of  oxygen. 

In  the  animal  body  the  food  is  the  fuel ;  with  a  proper  supply  of  oxygen  we 
obtain,  the  heat  given  out  during  its  oxidation  or  combustion.  In  winter,  when  we 
takje  exercise  in  a  cold  atmosphere,  and  when  consequently  the  amount  of  inspired 
oxygen  increases,  the  necessity  for  food  containing  carbon  and  hydrogen  increases 
in  the  same  ratio  ;  and  by  gratifying  the  appetite  thus  excited,  we  obtain  the  most 
efficient  protection  against  the  most  piercing  cold.  A  starving  man  is  soon  frozen 
to  death.  The  animals  of  prey  in  the  arctic  regions,  as  every  one  knows,  far 
exceed  in  voracity  those  of  the  torrid  zone. 

In  cold  and  temperate  climates,  the  air,  which  incessantly  strives  to  consume  the 
body,  urges  man  to  laborious  efforts  in  order  to  furnish  the  means  of  resistance  to 


22  FAMILIAR  LETTERS  ON  CHEMISTRY. 

its  action,  while,  in  hot  climates,  the  necessity  of  labor  to  provide  food  is  far  less 
urgent. 

Our  clothing  is  merely  an  equivalent  for  a  certain  amount  of  food.  The  more 
warmly  we  are  clothed  the  less  urgent  becomes  the  appetite  for  food,  because  the 
loss  of  heat  by  cooling,  and  consequently  the  amount  of  heat  to  be  supplied  by  the 
food,  is  diminished. 

If  we  were  to  go  naked,  like  certain  savage  tribes,  or  if  in  hunting  or  fishing  we 
were  exposed  to  the  same  degree  of  cold  as  the  Samoyedes,  we  should  be  able  with 
ease  to  consume  ten  pounds  of  flesh,  and  perhaps  a  dozen  of  tallow  candles  into 
the  bargain,  daily,  as  warmly  clad  travellers  have  related  with  astonishment  of 
these  people.  We  should  then  also  be  able  to  take  the  same  quantity  of  brandy  or 
train  oil  without  bad  effects,  because  the  carbon  and  hydrogen  of  these  substances 
would  only  suffice  to  keep  up  the  equilibrium  between  the  external  temperature  and 
that  of  our  bodies. 

According  to  the  preceding  expositions,  the  quantity  of  food  is  regulated  by  the 
number  of  respirations,  by  the  temperature  of  the  air,  and  by  the  amount  of  heat 
given  off  to  the  surrounding  medium. 

No  isolated  fact,  apparently  opposed  to  this  statement,  can  affect  the  truth  of  this 
natural  law.  Without  temporary  or  permanent  injury  to  health,  the  Neapolitan 
cannot  take  more  carbon  and  hydrogen  in  the  shape  of  food  than  he  expires  as 
carbonic  acid  and  water ;  and  the  Esquimaux  cannot  expire  more  carbon  and 
hydrogen  than  he  takes  into  the  system  as  food,  unless  in  a  state  of  disease  or  of 
starvation.  Let  us  examine  these  states  a  little  more  closely. 

The  Englishman  in  Jamaica  perceives  with  regret  the  disappearance  of  hia 
appetite,  previously  a  source  of  frequently  recurring  enjoyment ;  and  he  succeeds 
by  the  use  of  cayenne  pepper  and  the  most  powerful  stimulants,  in  enabling 
himself  to  take  as  much  food  as  he  was  accustomed  to  eat  at  home.  But  the  whole 
of  the  carbon  thus  introduced  into  the  system  is  not  consumed ;  the  temperature 
of  the  air  is  too  high,  and  the  oppressive  heat  does  not  allow  him  to  increase  the 
number  of  respirations  by  active  exercise,  and  thus  to  proportion  the  waste  to  the 
amount  of  food  taken  ;  disease  of  some  kind,  therefore,  ensues. 

On  the  other  hand,  England  sends  her  sick  to  southern  regions,  where  the  amount 
of  the  oxygen  inspired  is  diminished  in  a  very  large  proportion.  Those  whose 
diseased  digestive  organs  have  in  a  greater  or  less  degree  lost  the  power  of  bringing 
the  food  into  the  state  best  adapted  for  oxidation,  and  therefore  are  less  able  to 
resist  the  oxidising  influence  of  the  atmosphere  of  their  native  climate,  obtain  a 
great  improvement  in  health.  The  diseased  organs  of  digestion  have  power  to 
place  the  diminished  amount  of  food  in  equilibrium  with  the  inspired  oxygen,  in 
the  mild  climate  ;  while  in  a  colder  region  the  organs  of  respiration  themselves 
would  have  been  consumed  in  furnishing  the  necessary  resistance  to  the  action  of 
the  atmospheric  oxygen. 

In  our  climate,  hepatic  diseases,  or  those  arising  from  excess  of  carbon,  prevail 
in  summer  ;  in  winter,  pulmonary  diseases,  or  those  arising  from  excess  of  oxygen, 
are  more  frequent. 

The  cooling  of  the  body,  by  whatever  cause  it  may  be  produced,  increases  the 
amount  of  food  necessary.  The  mere  exposure  to  the  open  air,  in  a  carriage  or  on 
the  deck  of  a  ship,  by  increasing  radiation  and  vaporisation,  increases  the  loss  of 
heat,  and  compels  us  to  eat  more  than  usual.  The  same  is  true  of  those  who  are 
accustomed  to  drink  large  quantities  of  cold  water,  which  is  given  off  at  the  tem- 
perature of  the  body,  98.5  degrees.  It  increases  the  appetite,  and  persons  of  weak 
constitution  find  it  necessary,  by  continued  exercise,  to  supply  to  the  system  the 
oxygen  required  to  restore  the  heat  abstracted  by  the  cold  water.  Loud  and  long 
continued  speaking,  the  crying  of  infants,  moist  air,  all  exert  a  decided  and 
appreciable  influence  on  the  amount  of  food  which  is  taken. 

We  have  assumed  that  it  is  especially  carbon  and  hydrogen  which,  by  combining 
with  oxygen,  serve  to  produce  animal  heat.  In  fact,  observation  proves  that  the 
hydrogen  of  the  food  plays  a  not  less  important  part  than  the  carbon. 

The  whole  process  of  respiration  appears  most  clearly  developed,  when  we 
consider  the  state  of  a  man,  or  other  animal,  totally  deprived  of  food. 

The  first  effect  of  starvation  is  the  disappearance  of  fat,  and  this  fat  cannot  b6 
traced  either  in  the  urine  or  in  the  scanty  faeces.  Its  carbon  and  hydrogen  have 
been  given  off  through  the  skin  and  lungs  in  the  form  of  oxidized  products  ;  it  is 
obvious  that  they  have  served  to  support  respiration. 

In  the  case  of  a  starving  man,  32£  ounces  of  oxygen  enter  the  system  daily,  and 
are  given  out  again  in  combination  with  a  part  of  his  body.  Currie  mentions  the 
ease  of  an  individual  who  was  unable  to  swallow,  and  whose  body  lost  one  hundred 
pounds  in  weight  during  a  month ;  and,  according  to  Martell  (Trans.  Linn.  Soc., 


FAMILIAR  LETTERS  ON  CHEMISTRY.  23 

vol.  xi.,  p.  411),  a  fat  pig,  overwhelmed  in  a  slip  of  earth,  lived  one  hundred  and 
sixty  days  without  food,  and  was  found  to  have  diminished  in  weight,  in  that  time, 
more  than  one  hundred  and  twenty  pounds.  The  whole  history  of  hybernating 
animals,  and  the  well  established  facts  of  the  periodical  accumulation,  in  various 
animals,  of  fat,  which,  at  other  periods,  entirely  disappears,  prove  that  the  oxygen, 
in  the  respiratory  process,  consumes,  without  exception,  all  such  substances  as  are 
capable  of  entering  into  combination  with  it.  It  combines  with  whatever  is 
presented  to  it ;  and  the  deficiency  of  hydrogen  is  the  only  reason  why  carbonic 
acid  is  the  chief  product ;  for,  at  the  temperature  of  the  body,  the  affinity  of 
hydrogen  for  oxygen  far  surpasses  that  of  carbon  for  the  same  element. 

We  know,  in  fact,  that  the  graminivora  expire  a  volume  of  carbonic  acid  equal 
to  that  of  the  oxygen  inspired,  while  the  carnivora,  the  only  class  of  animals  whose 
food  contains  fat,  inspire  more  oxygen  than  is  equal  in  volume  to  the  carbonic  acid 
expired.  Exact  experiments  have  shown,  that  in  many  cases  only  half  the  volume 
of  oxygen  is  expired  in  the  form  of  carbonic  acid.  These  observations  cannot  be 
gainsaid,  and  are  far  more  convincing  than  those  arbitrary  and  artificially  produced 
phenomena,  sometimes  called  experiments  ;  experiments  which,  made  as  too  often 
they  are,  without  regard  to  the  necessary  and  natural  conditions,  possess  no  value, 
and  may  be  entirely  dispensed  with  ;  especially  when,  as  in  the  present  case,  nature 
affords  the  opportunity  for  observation,  and  when  we  make  a  rational  use  of  that 
opportunity. 

In  the  progress  of  starvation,  however,  it  is  not  only  the  fat  which  disappears, 
but  also,  by  degrees,  all  such  of  the  solids  as  are  capable  of  being  dissolved.  In 
the  wasted  bodies  of  those  who  have  suffered  starvation,  the  muscles  are  shrunk 
and  unnaturally  soft,  and  have  lost  their  contractility  ;  all  those  parts  of  the  body 
•which  were  capable  of  entering  into  the  state  of  motion  have  served  to  protect  the 
remainder  of  the  frame  from  the  destructive  influence  of  the  atmosphere.  Toward 
the  end,  the  particles  of  the  brain  begin  to  undergo  the  process  of  oxidation,  and 
delirium,  mania,  and  death  close  the  scene ;  that  is  to  say,  all  resistance  to  the 
oxidizing  power  of  the  atmospheric  oxygen  ceases,  and  the  chemical  process  of 
eremacausis,  or  decay,  commences,  in  which  every  part  of  the  body,  the  bones 
excepted,  enters  into  combination  with  oxygen. 

The  time  which  is  required  to  cause  death  by  starvation  depends  on  the  amount 
of  fat  in  the  body,  on  the  degree  of  exercise,  as  in  labor  or  exertion  of  any  kind, 
on  the  temperature  of  the  air,  and  finally,  on  the  presence  or  absence  of  water. 
Through  the  skin  and  lungs  there  escapes  a  certain  quantity  of  water,  and  as  the 
presence  of  water  is  essential  to  the  continuance  of  the  vital  motions,  its  dissipation 
hastens  death.  Cases  have  occurred,  in  which  a  full  supply  of  water  being  acces- 
sible to  the  sufferer,  death  has  not  occurred  till  after  the  lapse  of  twenty  days.  In 
one  case,  life  was  sustained  in  this  way  for  the  period  of  sixty  days. 

In  all  chronic  diseases  death  is  produced  by  the  same  cause,  namely,  the  chemical 
action  of  the  atmosphere.  When  those  substances  are  wanting,  whose  function  in 
the  organism  is  to  support  the  process  of  respiration  ;  when  the  diseased  organs  are 
incapable  of  performing  their  proper  function  of  producing  these  substances  ;  when 
they  have  lost  the  power  of  transforming  the  food  into  that  shape  in  which  it  may, 
by  entering  into  combination  with  the  oxygen  of  the  air,  protect  the  system  from 
its  influence,  then,  the  substance  of  the  organs  themselves,  the  fat  of  the  body,  the 
substance  of  the  muscles,  the  nerves,  and  the  brain,  are  unavoidably  consumed. 
The  true  cause  of  death  in  these  cases  is  the  respiratory  process,  that  is,  the  action 
of  the  atmosphere. 

A  deficiency  of  food,  and  a  want  of  power  to  convert  the  food  into  a  part  of  the 
organism,  are  both,  equally,  a  want  of  resistance ;  and  this  is  the  negative  cause  of 
the  cessation  of  the  vital  process.  The  flame  is  extinguished,  because  the  oil  is 
consumed ;  and  it  is  the  oxygen  of  the  air  which  has  consumed  it. 

In  many  diseases  substances  are  produced  which  are  incapable  of  assimilation. 
By  the  mere  deprivation  of  food,  these  substances  are  removed  from  the  body  with- 
out leaving  a  trace  behind ;  their  elements  have  entered  into  combination  with  the 
oxygen  of  the  air. 

From  the  first  moment  that  the  function  of  the  lungs  or  of  the  skin  is  interrupted 
or  disturbed,  compounds,  rich  in  carbon,  appear  in  the  urine,  which  acquires  a 
brown  color.  Over  the  whole  surface  of  the  body  oxygen  is  absorbed,  and  combines 
with  all  the  substances  which  offer  no  resistance  to  it.  In  those  parts  of  the  body 
where  the  access  of  oxygen  is  impeded  ;  for  example,  in  the  arm-pits,  or  in  the  soles 
of  the  feet,  peculiar  compounds  are  given  out,  recognisable  by  their  appearance,  or 
by  their  odor.  These  compounds  contain  much  carbon. 

Respiration  is  the  falling  weight— the  bent  spring,  which  keeps  the  clock  in 
motion:  the  inspirations  and  expirations  are  the  strokes  of  the  pendulum  which 


\ 

FAMILIAR  LETTERS  OS  CHEMISTRY. 


regulate  it.  In  our  ordinary  time-pieces,  we  know  with  mathematical  accuracy  the 
effect  produced  on  their  rate  of  going,  by  changes  in  the  length  of  the  pendulum, 
or  in  the  external  temperature.  Few,  however,  have  a  clear  concep^n  of  the 
influence  of  air  and  temperature  on  the  health  of  the  human  body  ;  and  yet  the 
research  into  the  conditions  necessary  to  keep  it  in  the  normal  state,  is  not  more 
difficult  than  in  the  case  of  a  clock. 


LETTER  VIII. 

MY  DEAR  SIR  : 

Having  attempted  in  my  last  letter  to  explain  to  you  the  simple  and  admirable 
office  subserved  by  the  oxygen  of  the  atmosphere  in  its  combination  with  carbon  in 
the  animal  body,  I  will  now  proceed  to  present  you  with  some  remarks  upon  those 
materials  which  sustain  its  mechanisms  in  motion,  and  keep  up  their  various  func- 
tions— namely,  the  Aliments. 

If  the  increase  of  mass  in  an  animal  body,  the  development  and  reproduction  of 

its  organs  depend  upon  the  blood,  then  those  substances  only  which  are  capable  of 

being  converted  into  blood  can  be  properly  regarded  as  nourishment.     In  order 

I  then  to  ascertain  what  parts  of  our  food  are  nutritious,  we  must  compare  the  com- 

I  position  of  the  blood  with  the  composition  of  the  various  articles  taken  as  food. 

Two  substances  require  especial  consideration  as  the  chief  ingredients  of  the 
blood ;  one  of  these  separates  immediately  from  the  blood  when  it  is  withdrawn 
from  the  circulation. 

It  is  well  known  that  in  this  case  blood  coagulates,  and  separates  into  a  yellowish 
liquid,  the  serum  of  the  blood,  and  a  gelatinous  mass,  which  adheres  to  a  rod  or 
Btick  in  soft,  elastic  fibres,  when  coagulating  blood  is  briskly  stirred.  This  is  the 
fibrine  of  the  blood,  which  is  identical  in  all  its  properties  with  muscular  fibre, 
when  the  latter  is  purified  from  all  foreign  matters. 

The  second  principal  ingredient  of  the  blood  is  contained  in  the  serum,  and  gives 
to  this  liquid  all  the  properties  of  the  white  of  eggs,  with  which  it  is  indeed  iden- 
tical. When  heated,  it  coagulates  into  a  white  elastic  mass,  and  the  coagulating 
substance  is  called  albumen. 

Fibrine  and  albumen,  the  chief  ingredients  of  blood,  contain,  in  all,  seven  che- 
mical elements,  among  which  nitrogen,  phosphorus,  and  sulphur,  are  found.  They 
contain  also  the  earth  of  bones.  The  serum  retains  in  solution  sea  salt  and  other 
salts  of  potash  and  soda,  in  which  the  acids  are  carbonic,  phosphoric,  and  sulphu- 
ric acids.  The  globules  of  the  blood  contain  fibrine  and  albumen,  along  with  a  red 
coloring  matter,  in  which  iron  is  a  constant  element.  Beside  these,  the  blood  con- 
tains certain  fatty  bodies  in  small  quantity,  which  differ  from  ordinary  fats  in 
several  of  their  properties. 

Chemical  analysis  has  led  to  the  remarkable  result,  that  fibrine  and  albumen 

contain  the  same  organic  elements  united  in  the  samejgroportion — that  is,  that 

/they  are   isomeric,  their  chemical  composition — the   proportion  of  their  ultimate 

(  elements — being  identical.     But  the  difference  of  their  external  properties  shows 

that  the  particles  of  which  they  are  composed  are  arranged  in  a  different  order. 

(See  ante,  page  16.) 

This  conclusion  has  lately  been  beautifully  confirmed  by  a  distinguished  physio- 
logist (D6nis),  who  has  succeeded  in  converting  fibrine  into  albumen ;  that  is, 
in  giving  it  the  solubility,  and  coagulability,  by  heat,  which  characterize  the  white 
of  eggs. 

Fibrine  and  albumen,  beside  having  the  same  composition,  agree  also  in  this, 
that  both  dissolve  in  concentrated  muriatic  acid,  yielding  a  solution  of  an  intense 
purple  color.  This  solution,  whether  made  with  fibrine  or  albumen,  has  the  very 
same  reactions  with  all  substances  yet  tried. 

Both  albumen  and  fibrine,  in  the  process  of  nutrition,  are  capable  of  being  con- 
verted into  muscular  fibre,  and  muscular  fibre  is  capable  of  being  reconverted  into 
blood.  These  facts  have  long  been  established  by  physiologists,  and  chemistry  has 
merely  proved  that  these  metamorphoses  can  be  accomplished  under  the  influence 
of  a  certain  force,  without  the  aid  of  a  third  substance,  or  of  its  elements,  and 
without  the  addition  of  any  foreign  element,  or  the  separation  of  any  element  pre- 
viously present  in  these  su' 


FAMILIAR  LETTERS  ON  CHEMISTRY.  25 

If  we  now  compare  the  composition  of  all  organized  parts  with  that  of  fibrine 
and  albumen,  the  following  relations  present  themselves : 

All  parts  of  the  animal  body  which  have  a  decided  shape,  which  form  parts  of 
organs,  contain  nitrogen.  No  part  of  an  organ  which  possesses  motion  and  life  is 
destitute  of  nitrogen  ;  all  of  them  contain  likewise  carbon  and  the  elements  of 
water ;  the  latter,  however,  in  no  case  in  the  proportion  to  form  water. 

The  chief  ingredients  of  the  blood  contain  nearly  seventeen  per  cent,  of  nitro- 
gen, and  from  numerous  analyses  it  appears  that  no  part  of  an  organ  contains  less 
than  seventeen  per  cent,  of  nitrogen. 

The  most  convincing  experiments  and  observations  have  proved  that  the  animal  \ 
body  is  absolutely  ^incapable  of  producing  an  elementary  body,  such  as  carbon  or  \ 
nitrogen,  out  of  suBstandJWWhich  do  not  contain  it;  and  it  obviously  follows,  that 
all  kinds  of  food  fit  for  the  production  either  of  blood,  or  of  cellular  tissue,  mem- 
branes, skin,  hair,  muscular  fibre,  &c.,  must  contain  a  certain  amount  of  nitrogen, 
because  that  element  is  essential  to  the  composition  of  the  above-named  organs  ; 
because  the  organs  cannot  create  it  from  the  other  elements  presented  to  them  ; 
and,  finally,  because  no  nitrogen  is  absorbed  from  the  atmosphere  in  the  vital 
process. 

The  substance  of  the  brain  and  nerves  contains  a  large  quantity  of  albumen, 
fi:  d,  in  addition  to  this,  two  peculiar  fatty  acids,  distinguished  from  other  fats  by 
containing  phosphorus  (phosphoric  acid).  One  of  these  contains  nitrogen  (Fremy). 

Finally,  water  and  common  fat  are  those  ingredients  of  the  body  which  are  des- 
titute of  nitrogen.  Both  are  amorphous,  or  unorganized,  and  only  so  far  take  part 
in  the  vital  process  as  that  their  presence  is  required  for  the  due  performance  of 
the  vital  functions.  The  inorganic  constituents  of  the  body  are  iron,  lime,  mag- 
nesia, common  salt,  and  the  alkalies. 

The  nutritive  process  is  seen  in  its  simplest  form  in  carnivorous  animals.  This 
class  of  animals  lives  on  the  blood  and  flesh  of  the  graminivora ;  but  this  blood 
and  flesh  are,  in  all  their  properties,  identical  with  their  own.  Neither  chemical 
nor  physiological  differences  can  be  discovered. 

The  nutriment  of  carnivorous  animals  is  derived  originally  from  blood  ;  in  their 
stomach  it  becomes  dissolved,  and  capable  of  reaching  all  other  parts  of  the  body ; 
in  its  passage  it  is  again  converted  into  blood,  and  from  this  blood  are  reproduced 
all  those  parts  of  their  organization  which  have  undergone  change  or  metamor- 
phosis. 

With  the  exception  of  hoofs,  hair,  feathers,  and  the  earth  of  bones,  every  part  of 
the  food  of  carnivorous  animals  is  capable  of  assimilation. 

In  a  chemical  sense,  therefore,  it  may  be  said  that  a  carnivorous  animal,  in  sup- 
porting the  vital  process,  consumes  itself.     That  which  serves  for  its  nutrition  is  i 
identical  with  those  parts  of  its  organization  which  are  to  be  renewed. 

The  process  of  nutrition  in  graminivorous  animals  appears  at  first  sight  altogether 
different.  Their  digestive 'organs  are  less  simple,  and  their  food  consists  of  vegeta- 
bles, the  great  mass  of  which  contains  but  little  nitrogen. 

From  what  substances,  it  may  be  asked,  is  the  blood  formed,  by  means  of  which 
their  organs  are  developed  ?  This  question  may  be  answered  with  certainty. 

Chemical  researches  have  shown,  that  all  such  parts  of  vegetables  as  can  afford 
nutriment  to  animals  contain  certain  constituents  which  are  rich  in  nitrogen ;  and 
the  most  ordinary  experience  proves  that  animals  require  for  their  support  and 
nutrition  less  of  these  parts  of  plants  in  proportion  as  they  abound  in  the  nitro- 
genized  constituents.  Animals  cannot  be  fed  on  matters  destitute  of  these  nitro- 
genized  constituents. 

These  important  products  of  vegetation  are  especially  abundant  in  the  seeds  of 
the  different  kinds  of  grain,  and  of  peas,  beans,  and  lentils ;  in  the  roots  and  the 
juices  of  what  are  commonly  called  vegetables.  They  exist,  however,  in  all  plants, 
without  exception,  and  in  every  part  of  plants  in  larger  or  smaller  quantity. 

These  nitrogenized  forms  of  nutriment  in  the  vegetable  kingdom  may  be  reduced1 
to  three  substances,  which  are  easily  distinguished  by  their  external  characters. 
Two  of  them  are  soluble  in  water,  the  third  is  insoluble. 

When  the  newly-expressed  juices  of  vegetables  are  allowed  to  stand,  a  separation 
takes  place  in  a  few  minutes.  A  gelatinous  precipitate,  commonly  of  a  green  tinge, 
is  deposited,  and  this,  when  acted  on  by  liquids  which  remove  the  coloring  matter,, 
leaves  a  grayish  white  substance,  well  known  to  druggists  as  the  deposite  from 
vegetable  juices.  This  is  one  of  the  nitrogenized  compounds  which  serves  for  the 
nutrition  of  animals,  and  has  been  named  vegetable  jibrine.  The  juice  of  grapes  is 
especially  rich  in  this  constituent,  but  it  is  most  abundant  in  the  seeds  of  wheat, 
and  of  the  cerealia  generally.  It  may  be  obtained  from  wheat  flour  by  a  mecha- 
nical operation,  and  in  a  state  of  tolerable  purity ;  it  is  then  called  gluten,  but  the 


26  FAMILIAR  LETTERS  ON  CHEMISTRY. 

glutinous  property  belongs,  not  to  vegetable  fibrine,  but  to  a  foreign  substance, 
present  in  small  quantity,  which  is  not  found  in  the  other  cerealia. 

The  method  by  which  it  is  obtained  sufficiently  proves  that  it  is  insoluble  in 
water ;  although  we  cannot  doubt  that  it  was  originally  dissolved  in  the  vegetable 
juice,  from  which  it  afterwards  separated,  exactly  as  fibrine  does  from  blood. 

The  second  nitrogenizod  compound  remains  dissolved  in  the  juice  after  the 
separation  of  the  fibrine.  It  does  not  separate  from  the  juice  at  the  ordinary 
temperature,  but  is  instantly  coagulated  when  the  liquid  containing  it  is  heated  to 
the  boiling  point. 

When  the  clarified  juice  of  nutritious  vegetables,  such  as  cauliflower,  asparagus, 
mangeiwurzel,  or  turnips,  is  made  to  boil,  a  coagulum  is  formed,  which  it  is  abso- 
lutely impossible  to  distinguish  from  the  substance  which  separates  as  a  coagulum, 
when  the  serum  of  blood,  or  the  white  of  an  egg,  diluted  with  water,  are  heated  to 
the  boiling  point.  This  is  vegetable  albumen.  It  is  found  in  the  greatest  abundance 
in  certain  seeds,  in  nuts,  almonds,  and  others,  in  which  the  starch  of  the  graminese 
is  replaced  by  oiL 

The  third  nitrogenized  constituent  of  the  vegetable  food  of  animals  is  vegetable 
easeine.  It  is  chiefly  found  in  the  seeds  of  peas,  beans,  lentils,  and  similar  legu- 
minous seeds.  Like  vegetable  albumen,  it  is  goluble  in  water,  but  differs  from  it 
in  this,  that  its  solution  is  jnot  coagulated  by  heat.  When  the  solution  is  heated  or 
evaporated,  a  skin  forms  on  its  surface,  and  the  addition  of  an  acid  causes  a  coagu- 
lum, just  as  in  animal  milk. 

These  three  nitrogenized  compounds,  vegetable  fibrine,  albumen,  and  easeine,  are 
the  true  nitrogenized  constituents  of  the  food  of  graminivorous  animals ;  all  other 
nitrogenized  compounds  occurring  in  plants,  are  either  rejected  by  animals,  as  in 
the  case  of  the  characteristic  principles  of  poisonous  and  medicinal  plants,  or  else 
they  occur  in  the  food  in  such  very  small  proportion,  that  they  cannot  possibly  con- 
tribute to  the  increase  of  mass  in  the  animal  body. 

The  chemical  analysis  of  these  three  substances  has  led  to  the  very  interesting 
result  that  they  contain  the  same  organic  elements,  united  in  the  same  proportion 
by  weight ;  and,  what  is  still  more  remarkable,  that  they  are  identical  in  composi- 
tion with  the  chief  constituents  of  blood,  animal  fibrine,  and  albumen.  They  all 
three  dissolve  in  concentrated  muriatic  acid  with  the  same  deep  purple  color,  and 
even  in  their  physical  characters,  animal  fibrine  and  albumen  are  in  no  respect 
different  from  vegetable  fibrine  and  albumen.  It  is  especially  to  be  noticed,  that 
hy  the  phrase,  identity  of  composition,  we  do  not  here  intend*  mere  similarity,  but 
that  even  in  regard  to  the  presence  and  relative  amount  of  sulphur,  phosphorus, 
and  phosphate  of  lime,  no  difference  can  be  observed.  How  beautifully  and  admi- 

Irably  simple,  with  the  aid  of  these  discoveries,  appears  the  process  of  nutrition  in 
animals — the  formation  of  their  organs,  in  which  vitality  chiefly  resides !  Those 
vegetable  principles,  which  in  animals  are  used  to  form  blood,  contain  the  chief 
constituents  of  blood,  fibrine  and  albumen,  ready  formed,  as  far  as  regards  their 
composition.  All  plants,  besides,  contain  a  certain  quantity  of  iron,  which  reap- 
pears in  the  coloring  matter  of  the  blood.  Vegetable  fibrine  and  animal  fibrine, 
vegetable  albumen  and  animal  albumen,  hardly  differ,  even  in  form ;  if  these  prin- 
ciples be  wanting  in  the  food,  the  nutrition  of  the  animal  is  arrested ;  and  when 
they  are  present,  the  graminivorous  animal  obtains  in  its  food  the  very  same  prin- 
ciples on  the  presence  of  which  the  nutrition  of  the  carnivora  entirely  depends. 

Vegetables  produce  in  their  organism  the  blood  of  all  animals,  for  the  carnivora, 
in  consuming  the  blood  and  flesh  of  the  graminivora,  consume,  strictly  speaking, 
only  the  vegetable  principles  which  have  served  for  the  nutrition  of  the  latter. 
Vegetable  fibrine  and  albumen  take  the  same  form  in  the  stomach  of  the  gramini- 
vorous animal  as  animal  fibrine  and  albumen  do  in  that  of  the  carnivorous  animal, 
j  From  what  has  been  said,  it  follows  that  the  development  of  the  animal  organism 
and  its  growth  are  dependent  on  the  reception  of  certain  principles  identical  with 
-the  chief  constituents  of  blood. 

In  this  sense  we  may  say  that  the  animal  organism  gives  to  blood  only  its  form  ; 
that  it  is  incapable  of  creating  blood  out  of  other  substances  which  do  not  already 
contain  the  chief  constituents  of  that  fluid.  We  cannot,  indeed,  maintain  that  the 
animal  organism  has  no  power  to  form  other  compounds,  for  we  know  that  it  is 
capable  of  producing  an  extensive  series  of  compounds,  differing  in  composition 
from  the  chief  constituents  of  blood  ;  but  these  last,  which  form  the  starting  point 
of  the  series,  it  cannot  produce. 

The  animal  organism  is  a  higher  kind  of  vegetable,  the  development  of  which 
begins  with  those  substances  with  the  production  of  which  the  life  of  an  ordinary 
vegetable  ends.  As  soon  as  the  latter  has  borne  seed,  it  dies,  or  a  period  of  its  life 
comes  to  a  termination. 


FAMILIAR  LETTERS  ON  CHEMISTRY.  27 

In  that  endless  series  of  compounds,  which  begins  with  carbonic  acid,  ammonia, 
and  water,  the  sources  of  the  nutrition  of  vegetables,  and  includes  the  most 
complex  constituents  of  the  animal  brain,  there  is  no  blank,  no  interruption.  The 
first  substance  capable  of  affording  nutriment  to  animals  is  the  last  product  of  the 
creative  energy  01  vegetables. 

The  substance  of  cellular  tissue  and  of  membranes,  of  the  brain  and  nerves, 
these  the  vegetable  cannot  produce. 

The  seemingly  miraculous  in  the  productive  agency  of  vegetables  disappears  in 
a  great  degree,  when  we  reflect  that  the  production  of  the  constituents  of  blood 
cannot  appear  more  surprising  than  the  occurrence  of  the  fat  of  beef  and  mutton 
in  cocoa  beans,  of  human  fat  in  olive-oil,  of  the  principal  ingredient  of  butter  in. 
palm  oil,  and  of  horse  fat  and  train-oil,  in  certain  oily  seedsu 


LETTER   IX, 

MY  DEAR  SIR  : 

The  facts  detailed  in  my  last  letter  will  satisfy  you  as  to  the  manner  in  which 
the  increase  of  mass  in  an  animal,  that  is  its  growth,  is  accomplished  ;  we  have 
still  to  consider  a  most  important  question,  namely,  the  function  performed  in  the 
animal  system  by  substances  destitute  of  nitrogen ;  such  as  sugar,  starch,  gum, 
pectine,  &c. 

The  most  extensive  class  of  animals,  the  graminivora,  cannot  live  without  these 
substances  ;  their  food  must  contain  a  certain  amount  of  one  or  more  of  them,  and 
if  these  compounds  are  not  supplied,  death  quickly  ensues. 

This  important  inquiry  extends  also  to  the  constituents  of  the  food  of  carnivorous 
animals  in  the  earliest  periods  of  life ;  for  this  food  also  contains  substances  which 
are  not  necessary  for  their  support  in  the  adult  state.  The  nutrition  of  the  young 
of  carnivora  is  obviously  accomplished  by  means  similar  to  those  by  which  the 
graminivora  are  nourished ;  their  development  is  dependent  on  the  supply  of  a  fluid, 
which  the  body  of  the  mother  secretes  in  the  shape  of  milk. 

Milk  contains  only  one  nitrogenised  constituent,  known  under  the  name  of 
caseine  ;  besides  this,  its  chief  ingredients  are  butter  (fat),  and  sugar  of  milk.  The 
blood  of  the  young  animal,  its  muscular  fibre,  cellular  tissue,  nervous  matter,  and 
bones,  must  nave  derived  their  origin  from  the  nitrogenised  constituent  of  milk — 
the  caseine  ;  for  butter  and  sugar  of  milk  contain  no  nitrogen. 

Now,  the  analysis  of  caseine  has  led  to  the  result,  which,  after  the  details  I  have 
given,  can  hardly  excite  your  surprise,  that  this  substance  also  is  identical  in  com- 
position with  the  chief  constituents  of  blood,  fibrine  and  albumen.  Nay  more — a 
comparison  of  its  properties  with  those  of  vegetable  caseine  has  shown— '-that  these 
two  substances  are  identical  in  all  their  properties  ;  insomuch,  that  certain  plants, 
such  as  peas,  beans,  and  lentils,  are  capable  of  producing  the  same  substance 
which  is  formed  from  the  blood  of  the  mother,  and  employed  in  yielding  the  blood 
of  the  young  animal. 

The  young  animal,  therefore,  receives  in  the  form  of  caseine — which  is  distin- 
guished from  fibrine  and  albumen  by  its  great  solubility,  and  by  not  coagulating 
when  heated — the  chief  constituent  of  the  mother's  blood.  To  convert  caseine  into 
blood  no  foreign  substance  is  required,  and  in  the  conversion  of  the  mother's  blood 
into  caseine,  no  elements  of  the  constituents  of  the  blood  have  been  separated. 
When  chemically  examined,  caseine  is  found  to  contain  a  much  larger  proportion 
of  the  earth  of  bones  than  blood  does,  and  that  in  a  very  soluble  form,  capable  of 
reaching  every  part  of  the  body.  Thus,  even  in  the  earliest  period  of  its  life,  the 
development  of  the  organs,  in  which  vitality  resides,  is,  in  the  carnivorous  animal, 
dependent  on  the  supply  of  a  substance,  identical  in  organic  composition  with  the 
chief  constituents  of  its  blood. 

What,  then,  is  the  use  of  the  butter  and  the  sugar  of  milk  ?  How  does  it  happen 
that  these  substances  are  indispensable  to  life  ? 

Butter  and  sugar  of  milk  contain  no  fixed  bases,  no  soda  or  potash.  Sugar  of 
milk  has  a  composition  closely  allied  to  that  of  the  other  kinds  of  sugar,  of  starch, 
and  of  gum  ;  all  of  them  contain  carbon  and  the  elements  of  water,  the  latter 
precisely  in  the  proportion  to  form  water. 

There  is  added,  therefore,  by  means  of  these  compounds,  to  the  nitrogenized 


28  FAMILIAR  LETTERS  ON  CHEMISTRY. 

constituents  of  food,  a  certain  amount  of  carbon ;  or,  as  in  the  case  of  butter,  of 
carbon  and  hydrogen ;  that  is,  an  excess  of  elements,  which  cannot  possibly  be 
employed  in  the  production  of  blood,  because  the  nitrogenised  substances  contained 
in  the  food  already  contain  exactly  the  amount  of  carbon  which  is  required  for  the 
production  of  fibrine  and  albumen. 

The  following  considerations  will  show  that  hardly  a  doubt  can  be  entertained, 
that  this  excess  of  carbon  alone,  or  of  carbon  and  hydrogen,  is  expended  in  the 
production  of  animal  heat,  and  serves  to  protect  the  organism  from  the  action  of 
the  atmospheric  oxygen,  which  is  required  for  the  production  of  fibrine  and 
albumen. 

In  an  adult  carnivorous  animal,  which  neither  gains  nor  loses  weight,  perceptibly, 
from  day  to  day,  its  nourishment,  the  waste  of  organized  tissue,  and  its  consump- 
tion of  oxygen,  stand  to  each  other  in  a  well-defined  and  fixed  relation. 

The  carbon  of  the  carbonic  acid  given  off,  with  that  of  the  urine;  the  nitrogen 
of  the  urine,  and  the  hydrogen  given  off  as  ammonia  and  water ;  these  elements, 
taken  together,  must  be  exactly  equal  in  weight  to  the  carbon,  nitrogen,  and  hydro- 
gen of  the  metamorphosed  tissues,  and  since  these  last  are  exactly  replaced  by  the 
food,  to  the  carbon,  nitrogen,  and  hydrogen  of  the  food.  Were  this  not  the  case, 
the  weight  of  the  animal  could  not  possibly  remain  unchanged. 

But,  in  the  young  of  the  carnivora,  the  weight  does  not  remain  unchanged ;  on 
the  contrary,  it  increases  from  day  to  day  by  an  appreciable  quantity. 

This  fact  presupposes,  that  the  assimilative  process  in  the  young  animal  is  more 
energetic,  more  intense,  than  the  process  of  transformation  in  the  existing  tissues. 
If  both  processes  were  equally  active,  the  weight  of  the  body  could  not  increase  ; 
and  were  the  waste  by  transformation  greater,  the  weight  of  the  body  would 
decrease. 

Now,  the  circulation  in  the  young  animal  is  not  weaker,  but,  on  the  contrary, 
more  rapid  ;  the  respirations  are  more  frequent ;  and,  for  equal  bulks,  the  consump- 
tion of  oxygen  must  be  greater  rather  than  smaller  in  the  young  than  in  the  adult 
animal.  But,  since  the  metamorphosis  of  organized  parts  goes  on  more  slowly, 
there  would  ensue  a  deficiency  of  those  substances,  the  carbon  and  hydrogen  of 
which  are  adapted  for  combination  with  oxygen ;  because,  in  the  carnivora,  it  is  the 
new  compounds,  produced  by  the  metamorphosis  of  organized  parts,  which  nature 
has  destined  to  furnish  the  necessary  resistance  to  the  action  of  the  oxygen,  and  to 
produce  animal  heat.  What  is  wanting  for  these  purposes  Infinite  Wisdom  has 
supplied  to  the  young  animal  in  its  natural  food. 

The  carbon  and  hydrogen  of  butter,  and  the  carbon  of  the  sugar  of  milk,  no  part 
of  either  of  which  can  yield  blood,  fibrine,  or  albumen,  are  destined  for  the  support 
of  the  respiratory  process,  at  an  age  when  a  greater  resistance  is  opposed  to  the 
metamorphosis  of  existing  organisms  ;  or,  in  other  words,  to  the  production  of  com- 
pounds, which,  in  the  adult  state,  are  produced  in  quantity  amply  sufficient  for  the 
purpose  of  respiration. 

The  young  animal  receives  the  constituents  of  its  blood  in  the  caseine  of  the 
milk.  A  metamorphosis  of  existing  organs  goes  on,  for  bile  and  urine  are 
secreted ;  the  matter  of  the  metamorphosed  parts  is  given  off  in  the  form  of  urine, 
of  carbonic  acid,  and  of  water ;  but  the  butter  and  sugar  of  milk  also  disappear ; 
they  cannot  be  detected  in  the  faeces. 

The  butter  and  sugar  of  milk  are  given  out  in  the  form  of  carbonic  acid  and 
water,  and  their  conversion  into  oxidized  products  furnishes  the  clearest  proof  that 
far  more  oxygen  is  absorbed  than  is  required  to  convert  the  carbon  and  hydrogen 
of  the  metamorphosed  tissues  into  carbonic  acid  and  water. 

The  change  and  metamorphosis  of  organized  tissues  going  on  in  the  vital  process 
in  the  young  animal,  consequently  yield,  in  a  given  time,  much  less  carbon  and 
hydrogen  in  the  form  adapted  for  the  respiratory  process  than  corresponds  to  the 
oxygen  taken  up  in  the  lungs.  The  substance  of  its  organized  parts  would  undergo 
a  more  rapid  consumption,  and  would  necessarily  yield  to  the  action  of  the  oxygen, 
were  not  the  deficiency  of  carbon  and  hydrogen  supplied  from  another  source. 

The  continued  increase  of  mass,  or  growth,  and  the  free  and  unimpeded  develop- 
ment of  the  organs  in  the  young  animal,  are  dependent  on  the  presence  of  foreign 
substances,  which,  in  the  nutritive  process,  have  no  other  function  than  to  protect 
the  newly-formed  organs  from  the  action  of  the  oxygen.  It  is  the  elements  of  these 
substances  which  unite  with  the  oxygen ;  the  organs  themselves  could  not  do  so 
without  being  consumed ;  that  is,  growth,  or  increase  of  mass  in  the  body—the 
consumption  of  oxygen  remaining  the  same — would  be  utterly  impossible. 

The  preceding  considerations  leave  no  doubt  as  to  the  purpose  for  which  Nature 
has  added  to  the  food  of  the  young  of  carnivorous  mammalia  substances  devoid  of 
nitrogen,  which  their  organism  cannot  employ  for  nutrition,  strictly  so  called,  that 


FAMILIAR  LETTERS  ON  CHEMISTRY.  29 

is,  for  the  production  of  blood  ;  substances  which  may  be  entirely  dispensed  with 
in  their  nourishment  in  the  adult  state.  In  the  young  of  carnivorous  birds,  the 
want  of  all  motion  is  an  obvious  cause  of  diminished  waste  in  the  organized  parts ; 
hence,  milk  is  not  provided  for  them. 

The  nutritive  process  in  the  carnivora  thus  presents  itself  under  two  distinct 
forms ;  one  of  which  we  again  meet  with  in  the  graminivora. 

In  graminivorous  animals,  we  observe,  that  during  their  whole  life,  their  exist- 
ence depends  on  a  supply  of  substances  having  a  composition  identical  with  that 
of  sugar  of  milk,  or  closely  resembling  it.  Every  thing  that  they  consume  as  food 
contains  a  Certain  quantity  of  starch,  gum,  or  sugar,  mixed  with  other  matters. 

The  function  performed  in  the  vital  process  of  the  graminivora  by  these  sub- 
stances is  indicated  in  a  very  clear  and  convincing  manner,  when  we  take  into  con- 
sideration the  very  small  relative  amount  of  the  carbon  which  these  animals  con- 
sume in  the  nitrogenized  constituents  of  their  food,  which  bears  no  proportion 
whatever  to  the  oxygen  absorbed  through  the  skin  and  lungs. 

A  horse,  for  example,  can  be  kept  in  perfectly  good  condition,  if  he  obtain  as 
food  fifteen  pounds  of  hay  and  four  and  a  half  pounds  of  oats,  daily.  If  we  now 
calculate  the  whole  amount  of  nitrogen  in  these  matters,  as  ascertained  by  analysis 
(1.5  per  cent,  in  the  hay,  2.2  per  cent,  in  the  oats),  in  the  form  of  blood,  that  is,  as 
h'brine  and  albumen,  with  the  due  proportion  of  water  in  blood  (eighty  per  cent.), 
the  horse  receives  daily  no  more  than  four  and  a  half  ounces  of  nitrogen,  corres- 
ponding to  about  eight  pounds  of  blood.  But  along  with  this  nitrogen,  that  is, 
combined  with  it  in  the  form  of  fibrine  or  albumen,  the  animal  receives  only  about 
fourteen  and  a  half  ounces  of  carbon. 

Without  going  further  into  the  calculation,  it  will  readily  be  admitted,  that  the 
volume  of  air  inspired  and  expired  by  a  horse,  the  quantity  of  oxygen  consumed, 
and,  as  a  necessary  consequence,  the  amount  of  carbonic  acid  given  out  by  the 
animal,  is  much  greater  than  in  the  respiratory  process  in  man.  But  an  adult  man 
consumes  daily  about  fourteen  ounces  of  carbon,  and  the  determination  of  Bous- 
singault,  according  to  which  a  horse  expires  seventy-nine  ounces  daily,  cannot  be 
very  far  from  the  truth. 

In  the  nitrogenized  constituents  of  his  food,  therefore, 'the  horse  receives  rather 
less  than  the  fifth  part  of  the  carbon  which  his  organism  requires  for  the  support 
of  the  respiratory  process  ;  and  we  see  that  the  wisdom  of  the  Creator  has  added  to 
his  food  the  four-fifths  which  are  wanting,  in  various  forms,  as  starch,  sugar,  &c., 
with  which  the  animal  must  be  supplied,  or  his  organism  will  be  destroyed  by  the 
action  of  the  oxygen. 

It  is  obvious,  that,  in  the  system  of  the  graminivora,  whose  food  contains  so  small 
a  portion,  relatively,  of  the  constituents  of  blood,  the  process  of  metamorphosis  in 
existing  tissues,  and  consequently  their  restoration  or  reproduction,  must  go  on  far 
less  rapidly  than  in  the  carnivora.  Were  this  not  the  case,  a  vegetation  a  thousand 
times  more  luxuriant  than  the  actual  one  would  not  suffice  for  their  nourishment. 
Sugar,  gum,  and  starch,  would  no  longer  be  necessary  to  support  life  in  these 
animals,  because,  in  that  case,  the  products  of  the  waste,  or  metamorphosis  of  the 
organized  tissues,  would  contain  enough  of  carbon  to  support  the  respiratory 
process. 


LETTER  X. 

MY  DEAR  SIR  : 

Let  me  now  apply  the  principles  announced  in  the  preceding  letters  to  the 
circumstances  of  our  own  species.  Man,  when  confined  to  animal  food,  requires 
for  his  support  and  nourishment  extensive  sources  of  food,  even  more  widely 
extended  than  the  lion  and  tiger,  because,  when  he  has  the  opportunity,  he  kills 
without  eating. 

A  nation  of  hunters,  on  a  limited  space,  is  utterly  incapable  of  increasing  its 
numbers  beyond  a  certain  point,  which  is  soon  attained.  The  carbon  necessary 
for  respiration  must  be  obtained  from  the  animals,  of  which  only  a  limited  number 
can  live  on  the  space  supposed.  These  animals  collect  from  plants  the  constituents 
of  their  organs  and  of  their  blood,  and  yield  them,  in  turn,  to  the  savages  who  live 
by  the  chase  alone.  They,  again,  receive  this  food  unaccompanied  by  those  com- 


30  FAMILIAR  LETTERS  ON  CHEMISTRY. 

pounds,  destitute  of  nitrogen,  which,  during  the  life  of  the  animals,  served  to 
support  the  respiratory  process.  In  such  men,  confined  to  an  animal  diet,  it  is  the 
carbon  of  the  flesh  and  of  the  blood  which  must  take  the  place  of  starch  and  sugar. 

But  fifteen  pounds  of  flesh  contain  no  more  carbon  than  four  pounds  of  starch,  and 
while  the  savage,  vrith-  one  animal  and  an  equal  weight  of  starch,  could  maintain 
life  and  health  for  a  certain  number  of  days,  he  would  be  compelled,  if  confined 
to  flesh  alone,  in  order  to  procure  the  carbon  necessary  for  respiration,  during  the 
game  time,  to  consume  five  such  animals. 

It  is  easy  to  see,  from  these  considerations,  how  close  the  connexion  is  between 
agriculture  and  the  multiplication  of  the  human  species.  The  cultivation  of  our 
crops  has  ultimately  no  other  object  than  the  production  of  a  maximum  of  those 
substances  which  are  adapted  for  assimilation  and  respiration,  in  the  smallest  pos- 
sible space.  Grain  and  other  nutritious  vegetables  yield  us,  not  only  in  starch, 
sugar,  and  gum,  the  carbon  which  protects  our  organs  from  the  action  of  oxygen, 
and  produces  in  the  organism  the  heat  which  is  essential  to  life,  but  also  in  the  form 
of  vegetable  fibrine,  albumen,  and  caseine,  our  blood,  from  which  the  other  parts  of 
our  body  are  developed. 

Man,  when  confined  to  animal  food,  respires,  like  the  carnivora,  at  the  expense 
of  the  matters  produced  by  the  metamorphosis  of  organized  tissues ;  and,  just  as 
the  lion,  tiger,  hyaena  in  the  cages  of  a  menagerie,  are  compelled  to  accelerate  the 
waste  of  the  organized  tissue  by  incessant  motion,  in  order  to  furnish  the  matter 
necessary  for  respiration,  so  the  savage,  for  the  very  same  object,  is  forced  to 
make  the  most  laborious  exertions,  and  go  through  a  vast  amount  of  muscular 
exercise.  He  is  compelled  to  consume  force  merely  in  order  to  supply  matter  for 
respiration. 

Cultivation  is  the  economy  of  force.  Science  teaches  us  the  simplest  means  of 
obtaining  the  greatest  effect  with  the  smallest  expenditure  of  power,  and  with  given 
means  to  produce  a  maximum  of  force.  The  unprofitable  exertion  of  power,  the 
waste  of  force  in  agriculture,  in  other  branches  of  industry,  in  science,  or  in  social 
economy,  is  characteristic  of  the  savage  state,  or  of  the  want  of  knowledge. 

In  accordance  with  what  I  have  already  stated,  you  will  perceive  that  the  sub- 
stafiCes,  of  which  tHe^food  of  man  is  composed,  may  be  divided  into  two  classes ; 
in(o!  nitrogenized  ancP  don-nitrogenized.  The  former  are  capable  of  conversion  into 
blood ;  the  latter  arMncapable  of  this  transformation. 

Out  of  those  substances,  which  are  adapted  to  the  formation  of  blood,  are  formed 
all  the  organized  tissues.  The  other  class  of  substances,  in  the  normal  state  of 
health,  serve  to  support  the  process  of  respiration.  The  former  may  be  called  the 
plastic  elements  of  nutrition;  the  latter,  elements  of  respiration. 

Among  the  former  we  reckon — 

Vegetable  fibrine.  Vegetable  Albumen. 

Vegetable  casine.  Animal  flesh. 

Animal  blood. 

Among  the  elements  of  respiration  in  our  food  are — 
Fat.  Pectine. 

Starch.  Bassorine. 

Gum.  Wine. 

Cane  Sugar.  Beer. 

Grape  Sugar.  Spirits. 

Sugar  of  milk. 

The  most  recent  and  exact  researches  have  established  as  a  universal  fact,  to 
which  nothing  yet  known  is  opposed,  that  the  nitrogenized  constituents  of  vegetable 
food  have  a  composition  identical  with  that  of  the  constituents  of  the  blood. 

No  nitrogenized  compound,  the  composition  of  which  differs  from  that  of  fibrine, 
albumen,  and  caseine,  is  capable  of  supporting  the  vital  process  in  animals. 

The  animal  organism  unquestionably  possesses  the  power  of  forming,  from  the 
constituents  of  its  blood,  the  substance  of  its  membranes  and  celular  tissue,  of  the 
nerves  and  brain,  and  of  the  organic  part  of  cartilages  and  bones.  But  the  blood 
must  be  supplied  to  it  ready  formed  in  every  thing  but  its  form — that  is,  in  its 
chemical  composition.  If  this  be  not  done,  a  period  is  rapidly  put  to  the  formation 
of  blood,  and  consequently  to  life. 

This  consideration  enables  us  easily  to  explain  how  it  happens  that  the  tissues 
yielding  gelatine  or  chondrine,  as,  for  example,  the  gelatine  of  skin  or  of  bones, 
are  not  adapted  for  the  support  of  the  vital  process ;  for  their  composition  is  diffe- 
rent from  that  of  fibrine  or  albumen.  It  is  obvious  that  this  means  nothing  more 
than  that  those  parts  of  the  animal  organism,  which  form  the  blood,  do  not  possess 
the  power  of  effecting  a  transformation  in  the  arrangement  of  the  elements  of  gela- 
tine, or  of  those  tissues  which  contain  it.  The  gelatinous  tissues,  the  gelatine  of  the 


FAMILIAR  LETTERS  ON  CHEMISTRY.  3} 

bones,  the  membranes,  the  cells,  and  the  skin,  suffer  in  the  animal  body,  under  the 
influence  of  oxygen  and  moisture,  a  progressive  alteration;  a  part  of  these  tissues 
is  separated,  and  must  be  restored  from  the  blood ;  but  this  alteration  and  restora- 
tion is  obviously  confined  within  very  narrow  limits. 

While,  in  the  body  of  a  starving  or  sick  individual,  the  fat  disappears,  and  the 
muscular  tissue  takes  once  more  the  form  of  blood,  we  find  that  the  tendons  and 
membranes  retain  their  natural  condition ;  the  limbs  of  the  dead  body  retain  their 
connexions,  which  depend  on  the  gelatinous  tissues. 

On  the  other  hand,  we  see  that  the  gelatine  of  bones  devoured  by  a  dog  entirely 
disappears,  while  only  the  bone  earth  is  found  in  his  excrements.  The  same  is 
true  of  a  man,  when  fed  on  food  rich  in  gelatine,  as  for  example,  strong  soup.  The 
gelatine  is  not  to  be  found  either  in  the  urine  or  in  the  faeces,  and  consequently 
nir.st  have  undergone  a  change,  and  must  have  served  some  purpose  in  the  animal 
economy.  It  is  clear  that  the  gelatine  must  be  expelled  from  the  body  in  a  form 
different  from  that  in  which  it  was  introduced  as  food. 

When  we  consider  the  transformation  of  the  albumen  of  the  blood  into  a  part  of 
an  organ  composed  of  fibrine,  the  identity  in  composition  of  the  two  substances 
renders  the  change  easily  conceivable.     Indeed,  we  find  the  change  of  a  dissolved  , 
substance  into  an  insoluble  organ  of  vitality,   chemically  speaking,  natural  and 
easily  explained,  on  account  of  this  very  identity  of  composition.      Hence,  the 
opinion  is  not  unworthy  of  a  closer  investigation,  that  gelatine,  when  taken  in  the' 
dissolved  state,  is  again  converted,  in  the  body,  into  celular  tissue,  membrane,  and 
cartilage ;  that  it  may  serve  for  the  re-production  of  such  parts  of  these  tissues  as 
have  been  wasted,  and  for  their  growth. 

And  when  the  powers  of  nutrition  in  the  whole  body  are  effected  by  a  change  of 
the  health,  then,  even  should  the  power  of  forming  blood  remain  the  same,  the 
organic  force  by  which  the  constituents  of  the  blood  are  transformed  into  cellular 
tissue  and  membranes  must  necessarily  be  enfeebled  by  sickness.    In  the  sick  man,'! 
the  intensity  of  the  vital  force,  its   power   to  produce  metamorphoses,  must  be  J 
diminished  as  well  in  the  stomach  as  in  all  other  parts  of  the  body.     In  this  con- 
dition, the  uniform  experience  of  practical  physicians  shows  that  gelatinous  mat- 
ters, in  a  dissolved  state,  exercise  a  most  decided  influence  on  the  state  of  the* 
health.     Given  in  a  form  adapted  for  assimilation,  they  serve  to  husband  the  vital! 
force,  just  as  may  be  done  in  the  case  "of  the"™sTomach,  by  due  preparation  of  the! 
food  in  general. 

Brittleness  in  the  bones  of  graminivorous  animals  is  clearly  owing  to  a  weakness 
in  those  parts  of  the  organism  whose  function  it  is  to  convert  the  constituents  of 
the  blood  into  cellular  tissue  and  membrane  ;  and  if  we 'can  trust  to  the  reports  of 
physicians  who  have  resided  in  the  East,  the  Turkish  women,  in  their  diet  of  rice, 
and  in  the  frequent  use  of  enemata  of  strong  soup,  have  united  the  conditions 
necessary  for  the  formation  both  of  cellular  tissue  and  of  fat. 


LETTER  XI 

MY  DEAR  SIR  : 

In  the  immense,  yet  limited  expanse  of  the  ocean,  the  animal  and  vegetable 
kingdoms  are  mutually  dependent  upon,  and  successive  to,  each  other.  The  animals 
obtain  their  constituent  elements  from  the  plants,  and  restore  them  to  the  water  in 
their  original  form,  when  they  again  serve  as  nourishment  to  a  new  generation  of 
plants. 

The  oxygen,  which  marine  animals  withdraw  in  their  respiration  from  the  air, 
dissolved  in  sea-water,  is  returned  to  the  water  by  the  vital  processes  of  sea  plants ; 
that  air  is  richer  in  oxygen  than  atmospheric  air,  containing  thirty-two  to  thirty- 
three  per  cent.,  while  the  latter  contains  only  twenty-one  per  cent.  Oxygen  also 
combines  with  the  products  of  the  putrefaction  "of  dead  animal  bodies,  changes  their 
carbon  into  carbonic  acid,  their  hydrogen  into  water,  and  their  nitrogen  assumes 
again  the  form  of  ammonia. 

Thus  we  observe  in  the  ocean  a  circulation  takes  place  without  the  addition  or 
abstraction  of  any  element,  unlimited  in  duration,  although  limited  in  extent, 
inasmuch  as  in  a  confined  space  the  nourishment  of  plants  exists  in  a  limited 
quantity. 


32  FAMILIAR  LETTERS  ON  CHEMISTRY. 

We  well  know  that  marine  plants  cannot  derive  a  supply  of  humus  for  their 
nourishment  through  their  roots.  Look  at  the  great  sea-tang,  the  Fucus  Gigantius: 
this  plant,  according  to  Cook,  reaches  a  height  of  three  hundred  and  sixty  feet,  and 
a  single  specimen,  with  its  immense  ramifications,  nourishes  thousands  of  marine 
animals;  yet  its  root  is  a  small  body,  no  larger  than  the  fist.  What  nourishment 
can  this  draw  from  a  naked  rock,  upon  the  surface  of  which  there  is  no  perceptible 
change?  It  is  quite  obvious  that  these  plants  require  only  a  hold — a  fastening  to 
prevent  a  change  of  place — as  a  counterpoise  to  their  specific  gravity,  which  is  less 
than  that  of  the  medium  in  which  they  float.  That  medium  provides  the  necessary 
nourishment,  and  presents  it  to  the  surface  of  every  part  of  the  plant.  Sea-water 
contains  not  only  carbonic  acid  and  ammonia,  but  the  alkaline  and  earthy  phos- 
phates and  carbonates  required  by  these  plants  for  their  growth,  and  which  we 
always  find  as  constant  constituents  of  their  ashes. 

All  experience  demonstrates  that  the  conditions  of  the  existence  of  marine  plants 
are  the  same  which  are  essential  to  terrestrial  plants.  But  the  latter  do  not  live 
like  sea  plants,  in  a  medium  which  contains  all  their  elements,  and  surrounds  with 
appropriate  nourishment  every  part  of  their  organs ;  on  the  contrary,  they  require 
two  media,  of  which  one,  namely  the  soil,  contains  those  essential  elements  which 
are  absent  from  the  medium  surrounding  them,  that  is,  the  atmosphere. 

Is  it  possible  that  we  could  ever  be  in  doubt  respecting  the  office  which  the  soil 
and  its  component  parts  subserve  in  the  existence  and  growth  of  vegetables  ? — that 
there  should  have  been  a  time  when  the  mineral  elements  of  plants  were  not 
regarded  as  absolutely  essential  to  their  vitality  ?  Has  not  the  same  circulation  been 
observed  on  the  surface  of  the  earth,  which  we  have  just  contemplated  in  the 
ocean — the  same  incessant  change,  disturbance,  and  restitution  of  equilibrium? 

Experience  in  agriculture  shows  that  the  production  of  vegetables  on  a  given  sur- 
face increases  with  the  supply  of  certain  matters,  originally  parts  of  the  soil  which 
had  been  taken  up  from  it  by  plants — the  excrements  of  man  and  animals.  These 
are  nothing  more  than  matters  derived  from  vegetable  food,  which  in  the  vital  pro- 
cesses of  animals,  or  after  their  death,  assume  again  the  form  under  which  they 
originally  existed,  as  parts  of  the  soil.  Now,  we  know  that  the  atmosphere  contains 
none  of  these  substances,  and,  therefore,  can  replace  none;  and  we  know  that  their 
removal  from  a  soil  destroys  its  fertility,  which  may  be  restored  and  increased  by  a 
new  supply. 

Is  it  possible,  after  so  many  decisive  investigations  into  the  origin  of  the  elements 
of  animals  and  vegetables,  the  use  of  the  alkalies,  of  lime  and  the  phosphates, 
any  doubt  can  exist  as  to  the  principles  upon  which  a  rational  agriculture  depends  ? 
Can  the  art  of  agriculture  be  based  upon  any  thing  but  the  restitution  of  a  dis- 
turbed equilibrium  ?  Can  it  be  imagined,  that  any  country,  however  rich  and 
fertile,  with  a  flourishing  commerce,  which  for  centuries  exports  its  produce  in  the 
shape  of  grain  and  cattle,  will  maintain  its  fertility,  if  the  same  commerce  does  not 
restore,  in  some  form  of  manure,  those  elements  which  have  been  removed  from  the 
soil,  and  which  cannot  be  replaced  by  the  atmosphere?  Must  not  the  same  fate 
await  every  such  country  which  has  actually  befallen  the  once  prolific  soil  of  Vir- 
ginia, now  in  many  parts  no  longer  able  to  grow  its  former  staple  productions- 
wheat  and  tobacco  ? 

In  the  large  towns  of  England  the  produce  both  of  English  and  foreign  agricul- 
ture is  largely  consumed  ;  elements  of  the  soil,  indispensable  to  plants,  do  not 
return  to  the  fields — contrivances  resulting  from  the  manners  and  customs  of  Eng- 
lish people,  and  peculiar  to  them,  render  it  difficult,  perhaps  impossible,  to  collect 
the  enormous  quantity  of  the  phosphates,  which  are  daily,  as  solid  and  liquid  excre- 
ments, carried  into  the  rivers.  These  phoshates,  although  present  in  the  soil  in  the 
smallest  quantity,  are  its  most  important  mineral  constituents.  It  was  observed 
that  many  English  fields  exhausted  in  that  manner,  immediately  doubled  their 
produce,  as  if  by  a  miracle,  when  dressed  with  bone-earth  imported  from  the  conti- 
nent. But  if  the  export  of  bones  from  Germany  is  continued  to  the  extent  it  has 
hitherto  reached,  our  soil  must  be  gradually  exhausted,  and  the  extent  of  our  loss 
may  be  estimated,  by  considering  that  one  pound  of  bones  contains  as  much  phos- 
phoric acid  as  a  hundred  weight  of  grain. 

The  imperfect  knowledge  of  nature,  and  the  properties  and  relations  of  matter, 
possessed  by  the  alchemists,  gave  rise,  in  their  time,  to  an  opinion  that  metals  as 
well  as  plants  could  be  produced  from  a  -seed.  The  regular  forms  and  ramifications 
seen  in  crystals,  they  imagined  to  be  the  leaves  and  branches  of  metal  plants ;  and 
as  they  saw  the  seed  of  plants  grow,  producing  root,  stem,  and  leaves,  and  again 
blossoms,  fruits,  and  seeds,  apparently  without  receiving  any  supply  of  appropriate 
material,  they  deemed  it  worthy  of  zealous  inquiry  to  discover  the  seed  of  gold,  and 
the  earth  necessary  for  its  development.  If  the  metal  seeds  were  once  obtained, 


FAMILIAR  LETTERS  OX  CHEMISTRY 


might  they  not  entertain  hope  of  their  growth?  Such  ideas  could  only  be  enter- 
tained when  nothing  was  known  of  the  atmosphere,  and  its  participation  with  tho 
earth,  in  administering  to  the  vital  processes  of  plants  and  animals.  Modern 
chemistry,  indeed,  produces  the  elements  of  water,  and  combining  them,  forms 
water  anew ;  but  it  does  not  create  those  elements — it  derives  them  from  water ;  the 
new-formed  artificial  water  has  been  water  before. 

Many  of  our  farmers  are  like  the  alchemists  of  old — they  are  searching  for  the 
miraculous  seed — the  means,  which,  without  any  further  supply  of  nourishment  to 
a  soil  scarcely  rich  enough  to  be  sprinkled  with  indigenous  plants,  shall  produce 
crops  of  grain  a  hundred  fold. 

The  experience  of  centuries,  nay,  of  thousands  of  years,  is  insufficient  to  guard 
men  against  these  fallacies;  our  only  security  from  these  and  similar  absurdities 
must  be  derived  from  a  correct  knowledge  of  scientific  principles. 

In  the  first  period  of  natural  philosophy  organic  life  was  supposed  to  be  derived 
from  water  only ;  afterward,  it  was  admitted  that  certain  elements  derived  from  the 
air  must  be  superadded  to  the  water ;  but  we  now  know  that  other  elements  must 
be  supplied  by  the  earth,  if  plants  are  to  thrive  and  multiply. 

The  amount  of  materials  contained  in  the  atmosphere,  suited  to  the  nourishment 
of  plants,  is  limited ;  but  it  must  be  abundantly  sufficient  to  cover  the  whole  surface 
of  the  earth  with  a  rich  vegetation.  Under  the  tropics,  and  in  those  parts  of  our 
globe  where  the  most  genial  conditions  of  fertility  exist — a  suitable  soil,  a  moist 
atmosphere,  and  a  high  temperature — vegetation  is  scarcely  limited  by  space ;  and, 
where  the  soil  is  wanting,  it  is  gradually  supplied  by  the  decaying  leaves,  bark,  and 
branches  of  plants.  It  is  obvious  there  is  no  deficiency  of  atmospheric  nourishment 
for  plants  in  those  regions,  nor  are  these  wanting  in  our  own  cultivated  fields :  all 
which  plants  require  for  their  development  is  conveyed  to  them  by  the  incessant 
motions  of  the  atrnoshere.  The  air  between  the  tropics  contains  no  more  than  that 
of  the  arctic  zones ;  and  yet  how  different  is  the  amount  of  produce  of  an  equal 
surface  of  land  in  the  two  situations ! 

This  is  easily  explicable.  All  the  plants  of  tropical  climates,  the  oil  and  wax 
palms,  the  sugar  cane,  &c.,  contain  only  a  small  quantity  of  the  elements  of  the 
blood  necessary  to  the  nutrition  of  animals,  as  compared  with  our  cultivated  plants. 

The  tubers  of  the  potato  in  Chili,  its  native  country,  where  the  plant  resembles  a 
shrub,  if  collected  from  an  acre  of  land,  would  scarcely  suffice  to  maintain  an  Irish 
family  for  a  single  day  (Darwin.)  The  result  of  cultivation  in  those  plants  which 
serve  as  food  is  to  produce  in  them  those  constituents  of  the  blood.  In  the  absence 
of  the  elements  essential  to  these  in  the  soil,  starch,  sugar,  and  woody  fibre,  are, 
perhaps,  formed ;  but  no  vegetable  fibrine,  albumen,  or  caseine.  If  we  intend  to 
produce  on  a  given  surface  of  soil  more  of  these  latter  matters  than  the  plants  can 
obtain  from  the  atmosphere,  or  receive  from  the  soil  of  the  same  surface  in  its 
uncultivated  and  normal  state,  we  must  create  an  artificial  atmosphere,  and  add  the 
needed  elements  to  the  soil. 

The  nourishment  which  must  be  supplied  in  a  given  time  to  different  plants,  in 
order  to  admit  a  free  and  unimpeded  growth,  is  very  unequal. 

On  pure  sand,  on  calcareous  soil,  on  naked  rocks,  only  a  few  genera  of  plants 
prosper,  and  these  are,  for  the  most  part,  perennial  plants.  They  require,  for  their 
slow  growth,  only  such  minute  quantities  of  mineral  substances  as  the  soil  can 
furnish,  which  may  be  totally  barren  for  other  species.  Annual,  and  especially 
summer  plants,  grow  and  attain  their  perfection  in  a  comparative  short  time ;  they 
therefore  do  not  prosper  on  a  soil  which  is  poor  in  those  mineral  substances  neces- 
sary to  their  development.  To  attain  a  maximum  in  height  in  the  short  period  of 
their  existence  the  nourishment  contained  in  the  atmosphere  is  not  sufficient.  If 
the  end  of  cultivation  is  to  be  obtained  we  must  create  in  the  soil  an  artificial 
atmosphere  of  carbonic  acid  and  ammonia ;  and  this  surplus  of  nourishment,  which 
the  leaves  cannot  appropriate  from  the  air,  must  be  taken  up  by  the  corresponding 
organs,  that  is,  the  roots,  from  the  soil.  But  the  ammonia,  together  with  the  car- 
bonic acid,  are  alone  insufficient  to  become  part  of  a  plant  destined  to  the  nourish- 
ment of  animals.  In  the  absence  of  the  alkalies,  the  phosphates  and  other  earthy 
salts,  no  vegetable  fibrine,  no  vegetable  easeine,  can  be  formed.  The  phosphoric  acid 
of  the  phosphate  of  lime,  indispensable  to  the  ceralia  and  other  vegetables  in  the 
formation  of  their  seeds,  is  separated  as  an  excrement,  in  great  quantities,  by  the 
rind  and  bark  of  ligneous  plants. 

How  different  are  the  evergreen  plants,  the  oleaginous  plants,  the  mosses,  the 
ferns,  and  the  pines,  from  our  annual  grasses,  the  ceralia  and  leguminous  vegetables  ! 
The  former,  at  every  time  of  the  day  during  winter  and  summer,  obtain  carbon 
through  their  leaves  by  absorbing  carbonic  acid  which  is  not  furnished  by  the 
barren  soil  on  which  they  grow ;  water  is  also  absorbed  and  retained  by  their 

3 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


coriaceous  or  fleshy  leaves  with  great  force.  They  lose  very  little  by  evaporation, 
compared  with  other  plants.  On  the  other  hand,  how  very  small  is  the  quantity  of 
mineral  substances  which  they  withdraw  from  the  soil  during  their  almost  constant 
growth  in  one  year,  in  comparison  with  the  quantity  which  one  crop  of  wheat  of  an 
equal  weight  receives  in  three  months  ! 

It  is  by  means  of  moisture  that  plants  receive  the  necessary  alkalies  and  salts 
from  the  soil.  In  dry  summers  a  phenomenon  is  observed,  which,  when  the  import- 
ance of  mineral  elements  to  the  life  of  a  plant  was  unknown,  could  not  be 
explained.  The  leaves  of  plants  first  developed  and  perfected,  and,  therefore, 
nearer  the  surface  of  the  soil,  shrivel  up  and  become  yellow,  lose  their  vitality,  and 
fall  off  while  the  plant  is  in  an  active  state  of  growth,  without  any  visible  cause. 
This  phenomenon  is  not  seen  in  moist  years,  nor  in  evergreen  plants,  and  but 
rarely  in  plants  which  have  long  and  deep  roots,  nor  is  it  seen  in  perennials  in 
autumn  and  winter. 

The  cause  of  this  premature  decay  is  now  obvious.  The  perfectly  developed 
leaves  absorb  continually  carbonic  acid  and  ammonia  from  the  atmosphere,  which 
are  converted  into  elements  of  new  leaves,  buds,  and  shoots  ;  but  this  metamorphosis 
cannot  be  effected  without  the  aid  of  the  alkalies,  and  other  mineral  substances.  If 
the  soil  is  moist,  the  latter  are  continually  supplied  to  an  adequate  amount,  and  the 
plant  retains  its  lively  green  color;  but  if  this  supply  ceases  from  a  want  of 
moisture  to  dissolve  the  mineral  elements,  a  separation  takes  place  in  the  plant 
jtself.  The  mineral  constituents  of  the  juice  are  withdrawn  from  the  leaves 
already  formed,  and  are  used  for  the  formation  of  the  young  shoots  ;  and  as  soon 
as  the  seeds  are  developed,  the  vitality  of  the  leaves  completely  ceases.  These 
withered  leaves  contaiu  only  minute  traces  of  soluble  salts,  while  the  buds  and 
ghoots  are  very  rich  in  them. 

On  the  other  hand,  it  has  been  observed,  that  where  a  soil  is  too  highly  impreg- 
nated with  soluble  saline  materials,  these  are  separated  upon  the  surface  of  the 
leaves.  This  happens  to  culinary  vegetables  especially,  whose  leaves  become 
covered  with  a  white  crust.  In  consequence  of  these  exudations  the  plant  sickens, 
its  organic  activity  decreases,  its  growth  is  disturbed  ;  and  if  this  state  continues 
long,  the  plant  dies.  This  is  most.frequently  seen  in  foliaceous  plants,  the  large 
surfaces  of  which  evaporate  considerable  quantities  of  water.  Carrots,  pumpkins, 
peas,  &c.,  are  frequently  thus  diseased,  when,  after  dry  weather,  the  plant  being 
near  its  full  growth,  the  soil  is  moistened  by  short  showers,  followed  again  by  dry 
weather.  The  rapid  evaporation  carries  off  the  water  absorbed  by  the  root,  and  this 
leaves  the  salts  in  the  plant  in  a  far  greater  quantity  than  it  can  assimilate.  These 
salts  effloresce  upon  the  surface  of  the  leaves,  and  if  they  are  herbaceous  and  juicy, 
produce  an  effect  upon  them  as  if  they  had  been  watered  with  a  solution  containing 
a  greater  quantity  of  salts  than  their  organism  can  bear. 

Of  two  plants  of  the  same  species,  this  disease  befalls  that  which  is  nearest  its 
perfection  ;  if  one  should  have  been  planted  later,  or  be  more  backward  in  its 
development,  the  same  external  cause  which  destroys  the  one  will  contribute  to  the 
growth  of  the  other. 


LETTER  XII. 

MY  DEAR  SIR: 

Having  now  occupied  several  letters  with  the  attempt  to  unravel,  by  means  of 
chemistry,  some  of  the  most  curious  functions  of  the  animal  body,  and,  as  I  hope, 
made  clear  to  yeu  the  distinctions  between  the  two  kinds  of  constituent  elements 
in  food,  and  the  purposes  they  severally  subserve  in  sustaining  life,  let  me  now 
direct  your  attention  to  a  scarcely  less  interesting  and  equally  important  subject — 
the  means  of  obtaining  from  a  given  surface  of  the  earth  the  largest  amount  of 
produce  adapted  to  the  food  of  man  and  animals. 

Agriculture  is  both  a  science  and  an  art.  The  knowledge  of  all  the  conditions  of 
the  life  of  vegetables,  the  origin  of  their  elements,  and  the  sources  of  their  nourish- 
ment, form  its  scientific  basis. 

From  this  knowledge  we  derive  certain  rules  for  the  exercise  of  the  ART,  the 
principles  upon  which  the  mechanical  operations  of  farming  depend,  the  usefulness 
or  necessity  of  these  for  preparing  the  soil  to  support  the  growth  of  plants,  and  for 


FAMILIAR  LETTERS  OX  CHEMISTRY. 


35 


removing  every  obnoxious  influence.  No  experience,  drawn  from  the  exercise  of 
the  art,  can  be  opposed  to  true  scientific  principles,  because  the  latter  should  include 
all  the  results  of  practical  operations,  and  are  in  some  instances  solely  derived  there- 
from. Theory  must  correspond  with  experience,  because  it  is  nothing  more  than 
the  reduction  of  a  series  of  phenomena  to  their  last  causes. 

A  field,  in  which  we  cultivate  the  same  plant  for  several  successive  years,  becomes 
barren  for  that  plant  in  a  period  varying  with  the  nature  of  the  soil :  in  one  field  it 
will  be  in  three,  in  another  in  seven,  in  a  third  in  twenty,  in  a  fourth  in  a  hundred 
years.  One  field  bears  wheat,  and  no  peas ;  another  beans  and  turnips,  but  no 
tobacco  ;  a  third  gives  a  plentiful  crop  of  turnips,  but  will  not  bear  clover.  What 
is  the  reason  that  a  field  loses  its  fertility  for  one  plant,  the  same  which  at  first 
flourished  there  ?  What  is  the  reason  one  kind  of  plant  succeeds  in  a  field  where 
another  fails  ? 

These  questions  belong  to  science. 

What  means  are  necessary  to  preserve  to  a  field  its  fertility  for  one  and  the  same 
plant? — what  to  render  one  field  fertile  for  two,  for  three,  for  all  plants? 

These  last  questions  are  put  by  Art,  but  they  cannot  be  answered  by  Art. 

If  a  farmer,  without  the  guidance  of  just  scientific  principles,  is  trying  experi- 
ments to  render  a  field  fertile  for  a  plant  which  it  otherwise  will  not  bear,  his 
prospect  of  success  is  very  small.  Thousands  of  farmers  try  such  experiments  in 
various  directions,  the  result  of  which  is  a  mass  of  practical  experience  forming  a 
method  of  cultivation  which  accomplishes  the  desired  end  for  certain  places ;  but 
the  same  method  frequently  does  not  succeed — it  indeed  ceases  to  be  applicable  to 
a  second  or  third  place  in  the  immediate  neighborhood.  How  large  a  capital,  and 
how  much  power,  are  wasted  in  these  experiments !  Very  different,  and  far  more 
secure,  is  the  path  indicated  by  SCIENCE  ;  it  exposes  us  to  no  danger  of  failing,  but 
on  the  contrary,  it  furnishes  us  with  every  guarantee  of  success.  If  the  cause  of 
failure — of  barrenness  in  the  soil  for  one  or  two  plants — has  been  discovered,  means 
to  remedy  it  may  readily  be  found. 

The  most  exact  observations  prove  that  the  method  of  cultivation  must  vary  with 
the  geognostical  condition  of  the  subsoil.  In  basalt,  graywacke,  porphyry,  sand- 
stone, limestone,  &c.,  are  certain  elements  indispensable  to  the  growth  of  plants,  and 
the  presence  of  which  renders  them  fertile.  This  fully  explains  the  difference  in 
the  necessary  methods  of  culture  for  different  places ;  since  it  is  obvious  that  the 
essential  elements  of  the  soil  must  vary  with  the  varieties  of  composition  of  the 
rocks,  from  the  disintegration  of  which  they  originated, 

Wheat,  clover,  turnips,  for  example,  each  require  certain  elements  from  the  soil ; 
they  will  not  flourish  where  the  appropriate  elements  are  absent.  Science  teaches 
us  what  elements  are  essential  to  every  species  of  plants  by  an  analysis  of  their 
ushes.  If,  therefore,  a  soil  is  found  wanting  in  any  of  those  elements,  we  dis- 
cover at  once  the  cause  of  its  barrenness,  and  its  removal  may  now  be  readily 
accomplished. 

The  empiric  attributes  all  his  success  to  the  mechanical  operations  of  agriculture  ; 
he  experiences  and  recognises  their  value,  without  inquiring  what  are  the  causes  of 
their  utility,  their  mode  of  action  :  and  yet  this  scientific  knowledge  is  of  the  highest 
importance  for  regulating  the  application  of  power  and  the  expenditure  of  capital 
— for  insuring  its  economical  expenditure  and  the  prevention  of  waste.  Can  it  be 
imagined  that  the  mere  passing  of  the  ploughshare,  or  the  harrow,  through  the  soil 
— the  mere  contact  of  the  iron — can  impart  fertility  miraculously  ?  Nobody,  per- 
haps, seriously  entertains  such  an  opinion.  Nevertheless,  the  modus  operandi  of 
these  mechanical  operations  is  by  no  means  generally  understood.  The  fact  is 
quite  certain,  that  careful  ploughing  exerts  the  most  favorable  influence :  the  sur- 
face is  thus  mechanically  divided,  changed,  increased,  and  renovated :  but  the 
ploughing  is  only  auxiliary  to  the  end  sought. 

In  the  effects  of  time,  in  what  in  Agriculture  are  technically  called  fallows — the 
repose  of  the  fields— we  recognise  by  science  certain  chemical  actions,  which  are 
continually  exercised  by  the  elements  of  the  atmosphere  upon  the  whole  surface  of 
our  globe.  By  the  action  of  its  oxygen  and  its  corbonic  acid,  aided  by  water,  rain, 
changes  of  temperature,  &c.,  certain  elementary  constituents  of  rocks,  or  of  their 
ruins,  which  form  the  soil  capable  of  cultivation,  are  rendered  soluble  in  water,  and 
consequently  become  separable  from  all  their  insoluble  parts. 

These  chemical  actions,  poetically  denominated  the  "  tooth  of  time,"  destroy  all 
the  works  of  man,  and  gradually  reduce  the  hardest  rocks  to  the  condition  of  dust. 
By  their  influence  the  necessary  elements  of  the  soil  become  fitted  for  assimilation 
by  plants ;  and  it  is  precisely  the  end  which  is  obtained  by  the  mechanical  opera- 
tions of  farming.  They  accelerate  the  decomposition  of  the  soil,  in  order  to  provide 
a  new  generation  of  plants  with  the  necessary  elements  in  a  condition  favorable  to 


36  FAMILIAR  LETTERS  ON  CHEMISTRY 

their  assimilation.  It  is  obvious  that  the  rapidity  of  the  decomposition  of  a  solid 
body  must  increase  with  the  extension  of  its  surface ;  the  more  points  of  contact 
we  offer  in  a  given  time  to  the  external  chemical  agent,  the  more  rapid  will  be  its 
action. 

The  chemist,  in  order  to  prepare  a  mineral  for  analyis,  to  decompose  it,  or  to 
increase  the  solubility  of  its  elements,  proceeds  in  the  same  way  as  the  farmer  deals 
with  his  fields — he  spares  no  labor  in  order  to  reduce  it  to  the  finest  powder;  he 
separates  the  impalpable  from  the  coarser  parts  by  washing,  and  repeats  his  me- 
chanical bruising  and  trituration,  being  assured  his  whole  process  will  fail  if  he  is 
inattentive  to  this  essential  and  preliminary  part  of  it. 

The  influence  which  the  increase  of  surface  exercises  upon  the  disintegration  of 
rocks,  and  upon  the  chemical  action  of  air  and  moisture,  is  strikingly  illustrated 
upon  a  large  scale  in  the  operations  pursued  in  the  gold  mines  of  Yaquil,  in  Chili. 
These  are  described  in  a  very  interesting  manner  by  Darwin.  The  rock  containing 
the  gold  ore  is  pounded  by  mills  into  the  finest  powder;  this  is  subjected  to  wash- 
ing, which  separates  the  lighter  particles  from  the  metallic ;  the  gold  sinks  to  the 
bottom,  while  a  stream  of  water  carries  away  the  lighter  earthy  parts  into  ponds, 
where  it  subsides  to  the  bottom  as  mud.  When  this  deposit  has  gradually  filled  up 
the  pond,  this  mud  is  taken  out  and  piled  in  heaps,  and  left  exposed  to  the  action 
of  the  atmosphere  and  moisture.  The  washing  completely  removes  all  the  soluble 
part  of  the  disintegrated  rock ;  the  insoluble  part,  moreover,  cannot  undergo  any 
further  change  while  it  is  covered  with  water,  and  so  excluded  from  the  influence 
of  the  atmoshere  at  the  bottom  of  the  pond.  But,  being  exposed  at  once  to  the  air 
and  moisture,  a  powerful  chemical  action  takes  place  in  the  whole  mass,  which 
becomes  indicated  by  an  efflorescence  of  salts  covering  the  whole  surface  of  the 
heaps  in  considerable  quantity.  After  being  exposed  for  two  or  three  years,  the 
mud  is  again  subjected  to  the  same  process  of  washing,  and  a  considerable  quantity 
of  gold  is  obtained,  this  having  been  separated  by  the  chemical  process  of  decom- 
position in  the  mass.  The  exposure  and  washing  of  the  same  mud  is  repeated  six 
or  seven  times,  and  at  every  washing  it  furnishes  a  new  quantity  of  gold,  although 
its  amount  diminishes  every  time. 

Precisely  similar  is  the  chemical  action  which  takes  place  in  the  soil  of  our  fields  ; 
and  we  accelerate  and  increase  it  by  the  mechanical  operations  of  agriculture.  By 
these  we  sever  and  extend  the  surface,  and  endeavor  to  make  every  atom  of  the  soil 
accessible  to  the  action  of  the  carbonic  acid  and  oxygen  of  the  atmosphere.  We 
thus  produce  a  stock  of  soluble  mineral  substances,  which  serve  as  nourishment  to 
a  new  generation  of  plants,  and  which  are  indispensable  to  their  growth  and 
prosperity. 


LETTER   XIII. 

MY  DEAR  SIR  : 

Having  in  my  last  letter  spoken  of  the  general  principles  upon  which  the 
science  and  art  of  agriculture  must  be  based,  let  me  now  direct  your  attention  to 
some  of  those  particulars,  which  will  more  forcibly  exhibit  the  connexion  between 
chemistry  and  agriculture,  and  demonstrate  the  impossibility  of  perfecting  the 
important  art  of  rearing  food  for  man  and  animals  without  a  profound  knowledge 
of  our  science. 

All  plants,  cultivated  as  food,  require  for  their  healthy  sustenance  the  alkalies 
and  alkaline  earths,  each  in  a  certain  proportion ;  and  in  addition  to  these,  the 
ceralia  do  not  succeed  in  a  soil  destitute  of  silica  in  a  soluble  condition.  The  com- 
binations of  this  substance,  found  as  natural  productions,  namely,  the  silicates, 
differ  greatly  in  the  degree  of  facility  with  which  they  undergo  decomposition,  in 
consequence  of  the  unequal  resistance  opposed  by  their  integral  parts  to  the  dissolv- 
ing power  of  the  atmospheric  agencies.  Thus,  the  granite  of  Corsica  degenerates 
into  a  powder  in  a  time  which  scarcely  suffices  to  deprive  the  polished  granite  of 
Heidelberg  of  its  lustre. 

Some  soils  abound  in  silicates  so  readily  decomposable,  that  in  every  one  or  two 
years,  as  much  silicate  of  potash  becomes  soluble  and  fitted  for  assimilation  as  is 
required  by  the  leaves  and  straw  of  a  crop  of  wheat.  In  Hungary,  extensive  dis- 
tricts are  not  uncommon  where  wheat  and  tobacco  have  been  grown  alternately 


FAMILIAR  LETTERS  ON  CHEMISTRY.  37 

upon  the  same  soil  for  centuries,  the  land  never  receiving  back  any  of  those  mineral 
elements  which  were  withdrawn  in  the  grain  and  straw.  On  the  other  hand,  there 
are  fields  in  which  the  necessary  amount  of  soluble  silicate  of  potash  for  a  single 
crop  of  wheat  is  not  separated  from  the  insoluble  masses  in  the  soil  in  less  than 
two,  three,  or  even  more  years. 

The  term  fallow,  in  Agriculture,  designates  that  period  in  which  the  soil,  left  to 
the  influence  of  the  atmosphere,  becomes  enriched  with  those  soluble  mineral  con- 
stituents. Fallow,  however,  does  not  generally  imply  an  entire  cessation  of  cultiva- 
tion, but  only  an  interval  in  the  growth  of  the  ceralia.  That  store  of  silicates  and 
alkalies  which  is  the  principal  condition  of  their  success  is  obtained,  if  potatoes  or 
turnips  are  grown  upon  the  same  fields  in  the  intermediate  periods,  since  these  crops 
do  not  abstract  a  particle  of  silica,  and  therefore  leave  the  field  equally  fertile  for 
the  following  crop  of  wheat. 

The  preceding  remarks  will  render  it  obvious  to  you,  that  the  mechanical  work- 
ing of  the  soil  is  the  simplest  and  cheapest  method  of  rendering  the  elements  of 
nutrition  contained  in  it  accessible  to  plants. 

But  it  may  be  asked,  Are  there  not  other  means  of  decomposing  the  soil  besides 
its  mechanical  subdivision  ? — are  there  not  substances,  which,  by  their  chemical 
operation,  shall  equally  well  or  better  render  its  constituents  suitable  for  entering 
into  vegetable  organisms?  Yes:  we  certainly  possess  such  substances,  and  one  of 
them,  namely,  quick-lime,  has  been  employed  for  the  last  century  past  in  England 
for  this  purpose ;  and  it  would  be  difficult  to  find  a  substance  better  adapted  to  this 
service,  as  it  is  simple,  and  in  almost  all  localities  cheap  and  easily  accessible. 

In  order  to  obtain  correct  views  respecting  the  effect  of  quick-lime  upon  the  soil, 
let  me  remind  you  of  the  first  process  employed  by  the  chemist  when  he  is  desirous 
of  analysing  a  mineral,  and  for  this  purpose  wishes  to  bring  its  elements  into  a 
soluble  state.  Let  the  mineral  to  be  examined  be,  for  instance,  feldspar ;  this  sab- 
stance,  taken  alone,  even  when  reduced  to  the  finest  powder,  requires  for  its  solution 
to  be  treated  with  an  acid  for  weeks  or  months ;  but  if  we  first  mix  it  with  quick-lime, 
and  expose  the  mixture  to  a  moderately  strong  heat,  the  lime  enters  into  chemical 
combination  with  certain  elements  of  the  feldspar,  and  its  alkali  (potass)  is  set  free. 
And  now,  the  acid,  even  without  heat,  dissolves  not  only  the  lime,  but  also  so  much 
of  the  silica  of  the  feldspar  as  to  form  a  transparent  jelly.  The  same  effect  which 
the  lime  in  this  process,  with  the  acid  of  heat,  exerts  upon  the  feldspar,  it  produces 
when  it  is  mixed  with  the  alkaline  argillaceous  silicates,  and  they  are  for  a  long 
time  kept  together  in  a  moist  state. 

Common  potters'  clay,  or  pipe-clay,  diffused  through  water,  and  added  to  milk  of 
lime,  thickens  immediately  upon  mixing;  and  if  the  mixture  is  kept  for  some  months, 
and  then  treated  with  acid,  the  clay  becomes  gelatinous,  which  it  would  not  have 
done  without  the  admixture  with  the  lime.  The  lime,  in  combining  with  the  elements 
of  the  clay  liquifies  it ;  and,  what  is  more  remarkable,  liberates  the  greater  part  of 
its  alkalies.  These  interesting  facts  were  first  observed  by  Fuchs,  at  Munich :  they 
have  not  only  led  to  a  more  intimate  knowledge  of  the  nature  and  properties  of  the 
hydraulic  cements,  but,  what  is  far  more  important,  they  explain  the  effects  of 
caustic  lime  upon  the  soil,  and  guide  the  agriculturist  in  the  application  of  an 
invaluable  means  of  opening  it,  and  setting  free  its  alkalies — substances  so  im- 
portant, nay,  so  indispensable  to  his  crop. 

In  the  month  of  October  the  fields  of  Yorkshire  and  Oxfordshire  look  as  if  they 
were  covered  with  snow.  Whole  square  miles  are  seen  whitened  over  with  quick- 
lime, which,  during  the  moist  winter  months,  exercises  its  beneficial  influence  upon 
the  stiff,  clayey  soil,  of  those  counties. 

According  to  the  humus  theory,  quicklime  ought  to  exert  the  most  noxious 
influence  upon  the  soil,  because  all  organic  matters  contained  in  it  are  destroyed 
by  it,  and  rendered  incapable  of  yielding  their  humus  to  a  new  vegetation.  The 
facts  are  indeed  directly  contrary  to  this  now  abandoned  theory :  the  fertility  of  the 
soil  is  increased  by  the  lime. 

The  ceralia  require  the  alkalies  and  alkaline  silicates,  which  the  action  of  the 
lime  renders  fit  for  assimilation  by  the  plants.  If,  in  addition  to  these,  there  is  any 
decaying  organic  matter  present  in  the  soil  supplying  carbonic  acid,  it  may  facili- 
tate their  development ;  but  it  is  not  essential  to  their  growth.  If  we  furnish  the 
soil  with  ammonia,  and  the  phosphates,  which  are  indispensable  to  the  ceralia,  with 
the  alkaline  silicates,  we  have  all  the  conditions  necessary  to  ensure  an  abundant 
harvest.  The  atmosphere  is  an  inexhaustible  store  of  carbonic  acid. 

A  no  less  favorable  influence  than  that  of  lime  is  exercised  upon  the  soil  of  peaty 
land  by  the  mere  act  of  burning  it:  this  greatly  enhances  its  fertility.  We  have 
not  long  been  acquainted  with  the  remarkable  change  which  the  properties  of  clay 
undergo  by  burning.  The  observation  was  first  made  in  the  process  of  analysing 


3g  FAMILIAR  LETTERS  ON  CHEMISTRY. 

the  clay  silicates.  Many  of  these,  in  their  natural  state,  are  not  acted  on  by  acids, 
but  they  become  perfectly  soluble  if  heated  to  redness  before  the  application  of  the 
acid.  This  property  belongs  to  potters'  clay,  pipe-clay,  loam,  and  many  different 
modifications  of  clay  in  soils.  In  their  natural  state  they  may  be  boiled  in  con- 
centrated sulphuric  acid,  without  sensible  change  ;  but  if  freely  burned,  as  is  done 
with  the  pipe-clay  in  many  alum  manufactories,  they  dissolve  in  the  acid  with  the 
greatest  facility,  the  contained  silica  being  separated  like  a  jelly  in  a  soluble  state. 
Potters'  clay  belongs  to  the  most  sterile  kinds  of  soil,  and  yet  it  contains  within  itself 
all  the  constituent  elements  essential  to  a  most  luxurious  growth  of  plants ;  but 
their  mere  presence  is  insufficient  to  secure  this  end.  The  soil  must  be  accessible 
to  the  atmosphere,  to  its  oxygen,  to  its  carbonic  acid  ; — these  must  penetrate  it,  in 
order  to  secure  the  conditions  necessary  to  a  happy  and  vigorous  development  of 
the  roots.  The  elements  present  must  be  brought  into  that  peculiar  state  of  com- 
bination which  will  enable  them  to  enter  into  plants.  Plastic  clay  is  wanting  in 
these  properties  ;  but  they  are  imparted  to  it  by  a  feeble  calcination. 

At  Hardwicke  Court,  near  Gloucester,  I  have  seen  a  garden  (Mr.  Baker's)  con- 
sisting of  a  stiff  clay,  which  was  perfectly  sterile,  become,  by  mere  burning, 
extremely  fertile.  The  operation  was  extended  to  a  depth  of  three  feet.  This  was 
an  expensive  process,  certainly ;  but  it  was  effectual. 

The  great  difference  in  the  properties  of  burnt  and  unburnt  clay  is  illustrated 
by  what  is  seen  in  brick  houses,  built  in  moist  situations.  In  the  towns  of  Flan- 
ders, for  instance,  where  most  buildings  are  of  brick,  efflorescences  of  salts  cover 
the  surfaces  of  the  walls,  like  a  white  nap,  within  a  few  days  after  they  are  erected. 
If  this  saline  incrustation  is  washed  away  by  the  rain,  it  soon  reappears ;  and  this 
is  even  observed  on  walls  which,  like  the  gateway  of  Lisle,  have  been  erected  for 
centuries.  These  saline  incrustations  consist  of  carbonates  and  sulphates,  with 
alkaline  bases ;  and  it  is  well  known  these  act  an  important  part  in  vegetation. 
The  influence  of  lime  in  their  production  is  manifested  by  their  appearing  first  at 
the  place  where  the  mortar  and  brick  come  into  contact. 

It  will  now  be  obvious  to  you,  that  in  a  mixture  of  clay  with  lime,  all  the  condi- 
tions exist  for  the  solution  of  the  silicated  clay,  and  the  solubility  of  the  alkaline 
silicates.  The  lime  gradually  dissolving  in  water  Charged  with  carbonic  acid,  acts 
like  milk  of  lime  upon  the  clay.  This  explains  also  the  favorable  influence  which 
marl  (by  which  term  all  those  varieties  of  clay  rich  in  lime  are  designated)  exerts 
upon  most  kinds  of  soil.  There  are  marly  soils  wjiich  surpass  all  others  in  fertility 
for  all  kinds  of  plants ;  but  I  believe  marl  in  a  burnt  etate  must  be  far  more 
effective,  as  well  as  other  materials  possessing  a  similar  composition ;  as,  for 
instance,  those  species  of  limestone  which  are  adapted  to  the  preparation  of 
hydraulic  cements — for  these  carry  to  the  soil  not  only  the  alkaline  bases  useful  to 
plants,  but  also  silica  in  a  state  capable  of  assimilation. 

The  ashes  of  coals  and  lignite  are  also  excellent  means  of  ameliorating  the  soil, 
and  they  are  used  in  many  places  for  this  purpose.  The  most  suitable  may  be 
readily  known  by  their  property  of  forming  a  gelatinous  mass  when  treated  with 
acids,  or  by  becoming,  when  mixed  with  cream  of  lime,  like  hydraulic  lime — solid 
and  hard  as  stone. 

I  have  now,  I  trust,  explained  to  your  satifaction,  that  the  mechanical  operations 
of  agriculture — the  application  of  lime  and  chalk  to  lands,  and  the  burning  of 
clay — depend  upon  one  and  the  same  scientific  principle :  they  are  means  of  acce- 
lerating the  decomposition  of  the  alkaline  clay  silicates,  in  order  to  provide  plants, 
at  the  beginning  of  a  new  vegetation,  with  certain  inorganic  matters  indispensable 
for  their  nutrition. 


LETTER   XIV. 

MY  DBA*  SIR  t 

I  treated,  in  my  last  letter,  of  the  means  of  improving  the  condition  of  the  soil 
for  agricultural  purposes  by  mechanical  operations  and  mineral  agents.  I  have 
now  to  speak  of  the  uses  and  effects  of  animal  exuviae,  and  vegetable  matters  or 
manures — properly  so  called. 

In  order  to  understand  the  nature  of  these,  and  the  peculiarity  of  their  influence 


FAMILIAR  LETTERS  ON  CHEMISTRY.  39 

upon  our  fields,  it  is  highly  important  to  keep  in  mind  the  source  whence  they  are 
derived. 

It  is  generally  known,  that  if  we  deprive  an  animal  of  food,  the  weight  of  its 
body  diminishes  during  every  moment  of  its  existence.  If  this  abstinence  is  con- 
tinued for  some  time,  the  diminution  becomes  apparent  to  the  eye ;  all  the  fat  of 
the  body  disappears,  the  muscles  decrease  in  firmness  and  bulk,  and,  if  the  animal 
is  allowed  to  die  starved,  scarcely  any  thing  but  skin,  tendon,  and  bones,  remain. 
This  emaciation  which  occurs  in  a  body  otherwise  healthy,  demonstrates  to  us,  that 
during  the  life  of  an  animal  every  part  of  its  living  substance  is  undergoing  a  per- 
petual change ;  all  its  component  parts,  assuming  the  form  of  lifeless  compounds, 
are  thrown  off  by  the  skin,  lungs,  and  urinary  system,  altered  more  or  less  by  the 
secretory  organs.  This  change  in  the  living  body  is  intimately  connected  with  the 
process  of  respiration ;  it  is,  in  truth,  occasioned  by  the  oxygen  of  the  atmosphere 
in  breathing,  which  combines  with  all  the  various  matters  within  the  body.  At 
every  inspiration  a  quantity  of  oxygen  passes  into  the  blood  in  the  lungs,  and 
unites  with  its  elements  ;  but  although  the  weight  of  the  oxygen  thus  daily  entering 
into  the  body  amounts  to  thirty-two  or  more  ounces,  yet  the  weight  of  the  body  is 
not  thereby  increased.  Exactly  as  much  oxygen  as  is  imbibed  in  inspiration  passes 
off  in  expiration,  in  the  form  of  carbonic  acid  and  water ;  so  that  with  every  breath 
the  amount  of  carbon  and  hydrogen  in  the  bodjr  is  diminished.  But  the  emacia- 
tion— the  loss  of  weight  by  starvation — does  not  simply  depend  upon  the  separation 
of  the  carbon  and  hydrogen  ;  but  all  the  other  substances  which  are  in  combination 
with  these  elements  in  the  living  tissues  pass  off  in  the  secretions.  The  nitrogen 
undergoes  a  change,  and  is  thrown  out  of  the  system  by  the  kidneys.  Their 
secretion,  the  urine,  contains  not  only  a  compound  rich  in  nitrogen,  namely  urea, 
but  the  sulphur  of  the  tissues  in  the  form  of  a  sulphate,  all  the  soluble  salts  of  the 
blood  and  animal  fluids,  common  salt,  the  phosphates,  soda,  and  potash.  The  car- 
bon and  hydrogen  of  the  blood  of  the  muscular  fibre,  and  of  all  the  animal  tissues 
which  can  undergo  change,  return  into  the  atmosphere.  The  nitrogen,  and  all  the 
soluble  inorganic  elements,  are  carried  to  the  earth  in  the  urine. 

These  changes  take  place  in  the  healthy  animal  body  during  every  moment  of 
life ;  a  waste  and  loss  of  substance  proceeds  continually ;  and  if  this  loss  is  to  be 
restored,  and  the  original  weight  and  substance  repaired,  an  adequate  supply  of 
materials  must  be  furnished  whence  the  blood  and  wasted  tissues  may  be  regene- 
rated. This  supply  is  obtained  from  the  food. 

In  an  adult  person  in  a  normal  or  healthy  condition,  no  sensible  increase  or 
decrease  of  weight  occurs  from  day^to  day.  In  youth  the  weight  of  the  body 
increases,  while  in  old  age  it  decreases.  There  can  be  no  doubt  that  in  the  adult 
the  food  has  exactly  replaced  the  loss  of  substance:  it  has  supplied. just  so  much 
carbon,  hydrogen,  nitrogen,  and  other  elements,  as  have  passed  through  the  skin, 
lungs,  and  urinary  organs.  In  youth  the  supply  is  greater  than  the  waste.  Part 
of  the  elements  of  the  food  remain  to  augment  the  bulk  of  the  body.  In  old  age 
the  waste  is  greater  than  the  supply,  and  the  body  diminishes.  It  is  unquestionable, 
that,  with  the  exception  of  a  certain  quantity  of  carbon  and  hydrogen,  which  are 
secreted  through  the  skin  and  lungs,  we  obtain,  in  the  solid  and  fluid  excrements 
of  man  and  animals,  all  the  elements  of  their  food. 

We  obtain  daily,  in  the  form  of  urea,  all  the  nitrogen  taken  in  the  food  both  of 
the  young  and  the  adult ;  and  further,  in  the  urine,  the  whole  amount  of  the  alkalies, 
soluble  phosphates  and  sulphates  contained  in  all  the  various  aliments.  In  the  solid 
excrements  are  found  all  those  substances  taken  in  the  food  which  have  undergone 
no  alteration  in  the  digestive  organs,  all  indigestible  matters,  such  as  woody  fibre, 
the  green  coloring  matter  of  leaves  (chlorophyle,)  wax,  &c. 

Physiology  teaches  us  that  the  process  of  nutrition  in  animals,  that  is,  their 
increase  of  bulk,  or  the  restoration  of  wasted  parts,  proceeds  from  the  blood.  In 
the  stomach  and  intestines,  therefore,  all  those  substances  in  the  food  capable  of 
conversion  into  blood  are  separated  from  its  other  constituents ;  in  other  words, 
during  the  passage  of  the  food  through  the  intestinal  canal  there  is  a  constant 
absorption  of  its  nitrogen,  since  only  azotized  substances  are  capable  of  conversion 
into  blood ;  and,  therefore,  the  solid  excrements  are  destitute  of  that  element,  except 
only  a  small  portion,  in  the  constitution  of  that  secretion  which  is  formed  to  facili- 
tate their  passage.  With  the  solid  excrements,  the  phosphates  of  lime  and  magnesia, 
which  were  contained  in  the  food  and  not  assimilated,  are  carried  off,  these  salts  being 
insoluble  in  water,  and  therefore  not  entering  the  urine. 

We  may  obtain  a  clear  insight  into  the  chemical  constitution  of  the  solid  excre- 
ments without  further  investigation,  by  comparing  the  faeces  of  a  dog  with  his  food. 
We  give  that  animal  flesh  and  bones — substances  rich  in  azotized  matter — and  we 
obtain,  as  the  last  product  of  its  digestion,  a  perfectly  white  excrement,  solid  while 


40  FAMILIAR  LETTERS  ON  CHEMISTRY. 

moist,  but  becoming  in  the  dry  air  a  powder.  This  is  the  phosphate  of  lime  of  the 
bones,  with  scarcely  one  per  cent,  of  foreign  organic  matter. 

Thus  we  see  that  in  the  solid  and  fluid  excrements  of  man  and  animals,  all  the 
nitrogen — in  short,  all  the  constituent  ingredients  of  the  consumed  food,  soluble  and 
insoluble,  are  returned ;  and  as  food  is  primarily  derived  from  the  fields,  we  possess 
in  those  excrements  all  the  ingredients  which  we  have  taken  from  it  in  the  form  of 
seeds,  roots,  or  herbs. 

One  part  of  the  crops  employed  for  fattening  sheep  and  cattle  is  consumed  by 
man  as  animal  food ;  another  part  is  taken  directly — as  flour,  potatoes,  green  vege- 
tables, &c. ;  a  third  portion  consists  of  vegetable  refuse,  and  straw  employed  as 
litter.  We  can,  it  is  obvious,  get  back  all  its  constituent  parts  which  have  been 
withdrawn  therefrom,  as  fruits,  grain,  and  animals,  in  the  fluid  and  solid  excre- 
ments of  man,  and  the  bones,  blood,  and  skins  of  the  slaughtered  animals.  It 
depends  upon  ourselves  to  collect  carefully  all  these  scattered  elements,  and  to 
restore  the  disturbed  equilibrium  of  composition  in  the  soil.  We  can  calculate 
exactly  how  much  and  which  of  the  component  parts  of  the  soil  we  export  in  a 
sheep  or  an  ox,  in  a  quarter  of  barley,  wheat,  or  potatoes,  and  ^ve  can  discover,  from 
the  known  composition  of  the  excrements  of  man  and  animals,  how  much  we  have 
to  supply  to  restore  what  is  lost  to  our  fields. 

If,  however,  we  could  procure  from  other  sources,  the  substances  which  give  to 
the  exuviae  of  man  and  animals  their  value  in  agriculture,  we  should  not  need  the 
latter.  It  is  quite  indifferent  for  our  purpose  whether  we  supply  the  ammonia  (the 
source  of  nitrogen)  in  the  form  of  urine,  or  in  that  of  a  salt  derived  from  coal-tar ; 
whether  we  derive  the  phosphate  of  lime  from  bones,  apatite,  or  fossil  excrements 
(the  coprolithes.) 

The  principal  problem  for  agriculture  is,  how  to  replace  those  substances  which 
have  been  taken  from  the  soil,  and  which  cannot  be  furnished  by  the  atmosphere. 
If  the  manure  supplies  an  imperfect  compensation  for  this  loss,  the  fertility  of  a 
field,  or  of  a  country,  decreases ;  if,  on  the  contrary,  more  are  given  to  the  fields, 
their  fertility  increases. 

An  importation  of  urine,  or  of  solid  excrements,  from  a  foreign  country,  is  equiva- 
lent to  an  importation  of  grain  and  cattle.  In  a  certain  time,  the  elements  of  those 
substances  assume  the  form  of  grain,  or  of  fodder,  then  become  flesh  and  bones, 
enter  into  the  human  body,  and  return  again  day  by  day  to  the  form  they  originally 


The  only  real  loss  of  elements  we  are  unable  to  prevent  is  of  the  phosphates, 
and  these,  in  accordance  with  the  customs  of  all  modern  nations,  are  deposited  in 
the  grave.  For  the  rest,  every  part  of  that  enormous  quantity  of  food  which  a  man 
consumes  during  his  lifetime  (say  in  sixty  or  seventy  years,}  which  was  derived 
from  the  fields,  can  be  obtained  and  returned  to  them.  We  know,  with  absolute 
certainty,  that  in  the  blood  of  a  young  or  growing  animal  there  remains  a  certain 
quantity  of  phosphate  of  lime  and  of  the  alkaline  phosphates,  to  be  stored  up  and 
minister  to  the  growth  of  the  bones  and  general  bulk  of  the  body,  and  that,  with 
the  exception  of  this  very  small  quantity,  we  receive  back,  in  the  solid  and  fluid 
excrements,  all  the  salts  and  alkaline  bases,  all  the  phosphate  of  lime  and  mag- 
nesia, and  consequently  all  the  inorganic  elements  which  the  animal  consumes  in 
its  food. 

We  can  thus  ascertain  precisely  the  quantity,  quality,  and  composition  of  animal 
excrements,  without  the  trouble  of  analysing  them.  If  we  give  a  horse  daily  4£ 
pounds'  weight  of  oats,  and  fifteen  pounds  of  hay,  and  knowing  that  oats  give  four 
per  cent,  and  hay  nine  per  cent,  of  ashes,  we  can  calculate  that  the  daily  excre- 
ments of  the  horse  will  contain  twenty-one  ounces  of  inorganic  matter  which  was 
drawn  from  the  fields.  By  analysis  we  can  determine  the  exact  relative  amount 
of  silica,  of  phosphates,  and  of  alkalies,  contained  in  the  ashes  of  the  oats  and  of 
the  hay. 

You  will  now  understand  that  the  constituents  of  the  solid  parts  of  animal 
excrements,  and  therefore  their  qualities  as  manure,  must  vary  with  the  nature  of 
the  creature's  food.  If  we  feed  a  cow  upon  beetroot,  or  potatoes,  without  hay, 
straw,  or  grain,  there  will  be  no  silica  in  her  solid  excrements,  but  there  will  be 
phosphate  of  lime  and  magnesia.  Her  fluid  excrements  will  contain  carbonate  of 
potash  and  soda,  together  with  compounds  of  the  same  bases  with  inorganic  acids. 
In  one  word,  we  have  in  the  fluid  excrements,  all  the  soluble  parts  of  the  ashes  of 
the  consumed  food ;  and  in  the  solid  excrements,  all  those  parts  of  the  ashes  which 
are  insoluble  in  water. 

If  the  food,  after  burning,  leaves  behind  ashes  containing  soluble  alkaline  phos- 
phates, as  is  the  case  with  bread,  seeds  of  all  kinds,  and  flesh,  we  obtain  from  the 
animal  by  which  they  are  consumed  a  urine  holding  in  solution  these  phosphates.  If, 


FAMILIAR  LETTERS  ON  CHEMISTRY.  4} 

however,  the  ashes  of  food  contain  no  alkaline  phosphates,  but  abound  in  insoluble 
earthy  phosphates,  as  hay,  carrots,  and  potatoes,  the  urine  will,  be  free  from  alka- 
line phosphates,  but  the  earthy  phosphates  will  be  found  in  the  faeces.  The  urine 
of  man,  of  carnivorous  and  graminivorous  animals,  contains  alkaline  phosphates; 
that  of  herbivorous  animals  is  free  from  the  salts. 

The  analysis  of  the  excrements  of  man,  of  the  piscivorous  birds  (as  the  guano,) 
of  the  horse,  and  of  cattle,  furnishes  us  with  the  precise  knowledge  of  the  salts 
they  contain,  and  demonstrates,  that  in  those  excrements,  we  return  to  the  fields 
the  ashes  of  the  plants  which  have  served  as  food — the  soluble  and  insoluble  salts 
and  earths  indispensable  to  the  development  of  cultivated  plants,  and  which  must 
be  furnished  to  them  by  a  fertile  soil. 

There  can  be  no  doubt  that,  in  supplying  these  excrements  to  the  soil,  we  return 
to  it  those  constituents  which  the  crops  have  removed  from  it,  and  we  renew  ita 
capability  of  nourishing  new  crops :  in  one  word,  we  restore  the  disturbed  equili- 
brium ;  and,  consequently,  knowing  that  the  elements  of  the  food  derived  from  the 
soil  enter  into  the  urine  and  solid  excrements  of  the  animals  it  nourishes,  we  can, 
with  the  greatest  facility,  determine  the  exact  value  of  the  different  kinds  of  ma- 
nure. Thus,  the  excrements  of  pigs,  which  we  have  fed  with  peas  and  potatoes, 
are  principally  suited  for  manuring  crops  of  potatoes  and  peas.  In  feeding  a  cow 
upon  hay  and  turnips,  we  obtain  a  manure  containing  the  inorganic  elements  of 
grasses  and  turnips,  and  which  is,  therefore,  preferable  for  manuring  turnips.  The 
excrement  of  pigeons  contains  the  mineral  elements  of  grain;  that  of  rabbits,  the 
elements  of  herbs  and  kitchen  vegetables.  The  fluid  and  solid  excrements  of  man, 
however,  contain  the  mineral  elements  of  grain  and  seeds  in  the  greatest  quantity. 


LETTER   XV. 

MY  DEAR  SIR: 

You  are  now  acquainted  with  my  opinions  respecting  the  effects  of  the  appli- 
cation of  mineral  agents  to  our  cultivated  fields,  arid  also  the  rationale  of  the 
influence  of  the  various  kinds  of  manure;  you  will,  therefore,  now  readily  under- 
stand what  I  have  further  to  say  of  the  sources  whence  the  carbon  and  nitrogen, 
indispensable  to  the  growth  of  plants,  are  derived. 

The  growth  of  forests,  and  the  produce  of  meadows,  demonstrate  that  an  inex- 
haustible quantity  of  carbon  is  furnished  for  vegetation  by  the  carbonic  acid  of 
the  atmosphere. 

We  obtain  from  an  equal  surface  of  forest,  or  meadow-land,  where  the  necessary 
mineral  elements  of  the  soil  are  present  in  a  suitable  state,  and  to  which  no  carbo- 
naceous matter  whatever  is  furnished  in  manures,  an  amount  of  carbon,  in  the 
shape  of  wood  arid  hay,  quite  equal,  and  ofttimes  more  than  is  produced  by  our 
fields,  in  grain,  roots,  and  straw,  upon  which  abundance  of  manure  has  been 
heaped. 

It  is  perfectly  obvious  that  the  atmosphere  must  furnish  to  our  cultivated  fields 
as  much  carbonic  acid,  as  it  does  to  an  equal  surface  of  forest  or  meadow,  and  that 
the  carbon  of  this  carbonic  acid  is  assimilated,  or  may  be  assimilated  by  the 
plants  growing  there,  provided  the  conditions  essential  to  its  assimilation,  and  be- 
coming a  constituent  element  of  vegetables,  exist  in  the  soil  of  these  fields. 

In  many  tropical  countries  the  produce  of  the  land  in  grain  or  roots,  during  the 
whole  year,  depends  upon  one  rain  in  the  spring.  If  this  rain  is  deficient  in  quan- 
tity, or  altogether  wanting,  the  expectation  of  an  abundant  harvest  is  diminished 
01  destroyed. 

Now  it  cannot  be  the  water  merely  which  produces  this  enlivening  and  fertilizing 
effect  observed,  and  which  lasts  for  weeks  and  months.  The  plant  receives,  by  means 
of  this  water,  at  the  time  of  its  first  development,  the  alkalies,  alkaline  earths,  and 
phosphates  necessary  to  its  organization.  If  these  elements,  which  are  necessary 
previous  to  its  assimilation  of  atmospheric  nourishment,  be  absent,  its  growth  is 
retarded.  In  fact,  the  development  of  a  plant  is  in  a  direct  ratio  to  the  amount  of 
the  matters  it  takes  up  from  the  soil.  If,  therefore,  a  soil  is  deficient  in  these 
mineral  constituents,  required  by  plants,  they  will  not  flourish  even  with  an  abun- 
dant supply  of  water. 

The  produce  of  carbon  on  a  meadow,  or  an  equal  surface  of  forest  land,  is  inde- 


42  FAMILIAR  LETTERS  ON  CHEMISTRY. 

pendent  of  a  supply  of  carbonaceous  manure,  but  it  depends  upon  the  presence  of 
certain  elements  of  the  soil  which  in  themselves  contain  no  carbon,  together  with 
the  existence  of  conditions  under  which  their  assimilation  by  plants  can  be  effected. 
We  increase  the  produce  of  our  cultivated  fields,  in  carbon,  by  a  supply  of  lime, 
ashes,  and  marl,  substances  which  cannot  furnish  carbon  to  the  plants,  and  yet  it 
is  indisputable — being  founded  upon  abundant  experience — that  in  these  substances 
we  furnish  to  the  fields  elements  which  greatly  increase  the  bulk  of  their  produce, 
and  consequently  the  amount  of  carbon. 

If  we  admit  these  facts  to  be  established,  we  can  no  longer  doubt  that  a  deficient 
produce  of  carbon,  or  in  other  words,  the  barrenness  of  a  field  does  not  depend 
upon  carbonic  acid,  because  we  are  able  to  increase  the  produce,  to  a  certain  degree, 
by  a  supply  of  substances  which  do  not  contain  any  carbon.  The  same  source, 
when  the  meadow  and  the  forest  are  furnished  with  carbon,  is  also  open  to  our  cul- 
tivated plants.  The  great  object  of  agriculture,  therefore,  is  to  discover  the  means 
best  adapted  to  enable  these  plants  to  assimilate  the  carbon  of  the  atmosphere  which 
exists  in  it  as  carbonic  acid.  In  furnishing  plants,  therefore,  with  mineral  elements, 
we  give  them  the  power  to  appropriate  carbon  from  a  source  which  is  inexhaustible ; 
while  in  the  absence  of  these  elements  the  most  abundant  supply  of  carbonic  acid, 
or  of  decaying  vegetable  matter,  would  not  increase  the  produce  of  a  field. 

With  an  adequate  and  equal  supply  of  these  essential  mineral  constituents  in  the 
soil,  the  amount  of  carbonic  acid  absorbed  by  a  plant  from  the  atmosphere  in  a 
given  time  is  limited  by  the  quantity  which  4s  brought  into  contact  with  its  organs 
of  absorption. 

The  withdrawal  of  carbonic  acid  from  the  atmosphere  by  the  vegetable  organism 
takes  place  chiefly  through  its  leaves ;  this  absorption  requires  the  contact  of  the 
carbonic  acid  with  their  surface,  or  with  the  part  of  the  plant  by  which  it  is 
absorbed. 

The  quantity  of  carbonic  acid  absorbed  in  a  given  time  is  in  direct  proportion  to 
the  surface  of  the  leaves,  and  the  amount  of  carbonic  acid  contained  in  the  air ; 
that  is,  two  plants  of  the  same  kind,  and  the  same  extent  of  surface  of  absorp- 
tion, in  equal  times  and  under  equal  conditions,  absorb  one  and  the  same  amount 
of  carbon. 

In  an  atmosphere  containing  a  double  proportion  of  carbonic  acid,  a  plant 
absorbs,  under  the  same  condition,  twice  the  quantity  of  carbon.  Boussingault 
observed,  that  the  leaves  of  the  vine,  enclosed  in  a  vessel,  withdrew  all  the  carbonic 
acid  from  a  current  of  air  which  was  passed  through  it,  however  great  its  velocity. 
(Dumas  Le9on,  p.  23.)  If,  therefore,  we  supply  double  the  quantity  of  carbonic  acid 
to  one  plant,  the  extent  of  the  surface  of  which  is  only  half  that  of  another 
living  in  ordinary  atmospheric  air,  the  former  will  obtain  and  appropriate  as  much 
carbon  as  the  latter.  Hence  results  the  effects  of  humus,  and  all  decaying  organic 
substances,  upon  vegetation.  If  we  suppose  all  the  conditions  for  the  absorption 
of  carbonic  acid  present,  a  young  plant  will  increase  in  mass,  in  a  limited  time, 
only  in  proportion  to  its  absorbing  surface  ;  but  if  we  create  in  the  soil  a  new  source 
of  carbonic  acid,  by  decaying  vegetable  substances,  and  the  roots  absorb  in  the  same 
time  three  times  as  much  carbonic  acid  from  the  soil  as  the  leaves  derive  from  the 
atmosphere,  the  plant  will  increase  in  weight  fourfold.  This  fourfold  increase 
extends  to  the  leaves,  buds,  stalks,  &c.,  and  in  the  increased  extent  of  surface,  the 
plant  acquires  an  increased  power  of  absorbing  nourishment  from  the  air,  which 
continues  in  action  far  beyond  the  time  when  its  derivation  of  carbonic  acid  through 
the  roots  ceases.  Humus,  as  a  source  of  carbonic  acid  in  cultivated  lands,  is  not 
only  useful  as  a  means  of  increasing  the  quantity  of  carbon — an  effect  which  in  most 
cases  may  be  very  indifferent  for  agricultural  purposes — but  the  mass  of  the  plant 
having  increased  rapidly  in  a  short  time,  space  is  obtained  for  the  assimilation  of 
the  elements  of  the  soil  necessary  for  the  formation  of  new  leaves  and  branches. 

Water  evaporates  incessantly  from  the  surface  of  the  young  plant ;  its  quantity 
is  in  direct  proportion  to  the  temperature  and  the  extent  of  the  surface.  The 
numerous  radical  fibrilliae  replace,  like  so  many  pumps,  the  evaporated  water ;  and 
so  long  as  the  soil  is  moist,  or  penetrated  with  water,  the  indispensable  elements 
of  the  soil,  dissolved  in  the  water,  are  supplied  to  the  plant.  The  water  absorbed 
by  the  plant  evaporating  in  an  aeriform  state,  leaves  the  saline  and  other  mineral 
constituents  within  it.  The  relative  proportion  of  these  elements  taken  up  by  a 
plant,  is  greater  the  more  extensive  the  surface  and  more  abundant  the  supply  of 
water ;  where  these  are  limited,  the  plant  soon  reaches  its  full  growth,  while  if  their 
supply  is  continued,  a  greater  amount  of  elements,  necessary  to  enable  it  to  appro- 
priate atmospheric  nourishment  being  obtained,  its  development  proceeds  much 
further.  The  quantity,  or  mass  of  seed  produced,  will  correspond  to  the  quantity 
of  mineral  constituents  present  in  the  plant.  That  plant,  therefore,  containing  the 


FAMILIAR  LETTERS  ON  CHEMISTRY.  43 

most  alkaline  phosphates  and  earthy  salts,  will  produce  more  or  a  greater  weight  of 
seeds  than  another  which,  in  an  equal  time,  has  absorbed  less  of  them.  We  con- 
sequently observe,  in  a  hot  summer,  when  a  further  supply  of  mineral  ingredient! 
from  the  soil  ceases  through  want  of  water,  that  the  height  and  strength  of  plants, 
as  well  as  the  development  of  their  seeds,  are  in  direct  proportion  to  its  absorption 
of  the  elementary  parts  of  the  soil  in  the  preceding  epochs  of  its  growth. 

The  fertility  of  the  year  depends  in  general  upon  the  temperature,  and  the 
moisture  or  dryness  of  the  spring,  if  all  the  conditions  necessary  to  the  assimilation 
of  the  atmospheric  nourishment  be  secured  to  our  cultivated  plants.  The  action 
of  humus,  then,  as  we  have  explain-ed  it  above,  is  chiefly  of  value  in  gaining  time. 
In  agriculture,  this  must  ever  be  taken  into  account ;  and  in  this  respect  humus  is 
of  importance  in  favoring  the  growth  of  vegetables,  cabbages,  &c. 

But  the  ceralia,  and  plants  grown  for  their  roots,  meet  on  our  fields,  in  the 
remains  of  the  preceding  crop,  with  a  quantity  of  decaying  vegetable  substances 
corresponding  to  their  contents  of  mineral  nutriment  from  the  soil,  and  consequently 
with  a  quantity  of  carbonic  acid  adequate  to  their  accelerated  development  in  the 
spring.  A  further  supply  of  carbonic  acid,  therefore,  would  be  quite  useless,  with- 
out a  corresponding  increase  of  mineral  ingredients. 

From  a  morgen  of  good  meadow  land,  two  thousand  five  hundred  pounds  weight 
of  hay,  according  to  the  best  agriculturists,  are  obtained  on  an  Average.  This 
amount  is  furnished  without  any  supply  of  organic  substances,  without  manure 
containing  carbon  or  nitrogen.  By  irrigation,  and  the  application  of  ashes  or 
gypsum,  double  that  amount  will  be  grown.  But  assuming  two  thousand  five 
hundred  pounds  weight  of  hay  to  be  the  maximum,  we  may  calculate  the  amount 
of  carbon  and  nitrogen  derived  from  the  atmosphere  by  the  plants  of  meadows. 

According  to  elementary  analysis,  hay,  dried  at  a  temperature  of  one  hundred 
degrees  of  Reaumur,  contains  45.8  per  cent,  of  carbon,  and  1.5  per  cent,  of  nitrogen. 
Fourteen  per  cent,  of  water  retained  by  the  hay,  dried  at  common  temperatures,  is 
driven  off  at  one  hundred  degrees.  Two  thousand  five  hundred  pounds  weight  of 
hay,  therefore,  corresponds  to  two  thousand  one  hundred  and  fifty  pounds,  dried  at 
one  hundred  degrees.  This  shows  us,  that  nine  hundred  and  eighty-four  pounds 
of  carbon,  and  32,2  pounds  weight  of  nitrogen,  have  been  obtained  in  the  produce 
of  one  morgen  of  meadow-land.  Supposing  that  this  nitrogen  has  been  absorbed 
by  the  plants  in  the  form  of  ammonia,  the  atmosphere  contains  39.1  pounds  weight 
of  ammonia  to  every  three  thousand  six  hundred  and  forty  pounds  weight  of 
carbonic  acid  (=984  carbon,  or  27  per  cent.);  or,  in  other  words,  to  every 
thousand  pounds  weight  of  carbonic  acid,  10/jths  pounds  of  ammonia,  that  is,  to 
about  Tirs'ffff^h  the  weight  of  the  air,  or  ^^^^th  of  its  volume. 

For  every  hundred  parts  of  carbonic  acid  absorbed  by  the  surface  of  the  leaves, 
the  plant  receives  from  the  atmosphere  somewhat  more  than  one  part  of  ammonia. 

With  every  thousand  pounds  of  carbon,  we  obtain — 

From  a  meadow        .        .        .    32T\ths  pounds  of  nitrogen. 
From  cultivated  fields — 

In  wheat  ,    21.5 


Oats 

%e       , 

Potatoes 
Beetroot 
Clover 
Peas 


22.3 

15.2 

34.1 

39.1 

44 

62 


Boussingault  obtained  from  his  farm  at  Bechelbronn,  in  Alsace,  in  five  years,  in 
the  shape  of  potatoes,  wheat,  clover,  turnips,  and  oats,  8383  of  carbon,  and  250.7 
nitrogen.  In  the  following  five  years,  as  beetroot,  wheat,  clover,  turnips,  oats, 
and  rye,  8,192  of  carbon,  and  284.2  of  nitrogen.  In  a  further  course  of  six  years, 
potatoes,  wheat,  clover,  turnips,  peas,  and  rye,  10,949  of  carbon,  356,6  of  nitrogen ; 
in  sixteen  years,  27,424  carbon,  858,5  nitrogen :  which  gives,  for  every  1,000  carbon, 
31.3  nitrogen. 

From  these  interesting  and  unquestionable  facts,  we  may  deduce  some  conclusions 
of  the  highest  importance  in  their  application  to  agriculture. 

1.  We  observe  that  the  relative  proportions  of  carbon  and  nitrogen,  stand  in  a 
fixed  relation  to  the  surface  of  the  leaves.     Those  plants  in  which  all  the  nitrogen 
may  be  said  to  be  concentrated  in  the  seeds,  as  the  ceralia,  contain  on  the  whole 
less  nitrogen  than  the  leguminous  plants,  peas  and  clover. 

2.  The  produce  of  nitrogen  on  a  meadow  which  receives  no  nitrogenized  manure, 
is  greater  than  that  of  a  field  of  wheat  which  has  been  manured. 


44  FAMILIAR  LETTERS  ON  CHEMISTRY. 

3.  The  produce  of  nitrogen  in  clover  and  peas,  which  agriculturists  will  acknow- 
ledge require  no  nitrogenized  manure,  is  far  greater  than  that  of  a  potato  or  turnip 
field,  which  is  abundantly  supplied  with  such  manures. 

Lastly  :  and  this  is  the  most  curious  deduction  to  be  derived  from  the  above  facts. 
If  we  plant  potatoes,  wheat,  turnips,  peas,  and  clover  (plants  containing  potash, 
lime,  and  silex),  upon  the  same  land,  three  times  manured,  we  gain  in  sixteen 
years,  for  a  given  quantity  of  carbon,  the  same  proportion  of  nitrogen  which  we 
receive  from  a  meadow  which  has  received  no  nitrogenized  manure. 

On  a  morgen  of  meadow  land,  we  obtain  in  plants,  containing  silex,  lime,  and 
potash,  984  carbon,  32.2  nitrogen.  On  a  morgen  of  cultivated  land,  in  an  average 
of  sixteen  years,  in  plants  containing  the  same  mineral  elements,  silex,  lime,  and 
potash,  857  carbon,  26.8  nitrogen. 

If  we  add  the  carbon  and  nitrogen  of  the  leaves  of  the  beetroot,  and  the  stalks 
and  leaves  of  the  potatoes,  which  have  not  been  taken  into  account,  it  still  remains 
evident  that  the  cultivated  fields,  notwithstanding  the  supply  of  carbonaceous  and 
nitrogenized  manures,  produced  no  more  carbon  and  nitrogen  than  an  equal  surface 
of  meadow  land  supplied  only  with  mineral  elements. 

What,  then,  is  the  rationale  of  the  effect  of  manure — of  the  solid  and  fluid  excre- 
ments of  animals  ? 

This  question  can  now  be  satisfactorily  answered :  that  effect  is  the  restoration 
of  the  elementary  constituents  of  the  soil  which  have  been  gradually  drawn  from 
it  in  the  shape  of  grain  and  cattle.  If  the  land  I  am  speaking  of  had  not  been 
manured  during  those  sixteen  years,  not  more  than  one  half,  or  perhaps  than  one 
third  part  of  the  carbon  and  nitrogen  would  have  been  produced.  We  owe  it  to 
the  animal  excrements,  that  it  equalled  in  production  the  meadow-land,  and  this, 
because  they  restored  the  mineral  ingredients  of  the  soil  removed  by  the  crops. 
All  that  the  supply  of  manure  accomplished,  was  to  prevent  the  land  from  becoming 
poorer  in  these,  than  the  meadow  which  produces  two  thousand  five  hundred  pounds 
of  hay.  We  withdraw  from  the  meadow  in  this  hay  as  large  an  amount  of  mineral 
substances  as  we  do  in  one  harvest  of  grain,  and  we  know  that  the  fertility  of  the 
meadow  is  just  as  dependent  upon  the  restoration  of  these  ingredients  to  its  soil, 
as  the  cultivated  land  is  upon  manures.  Two  meadows  of  equal  surface,  containing 
unequal  quantities  of  inorganic  elements  of  nourishment — other  conditions  being 
equal — are  very  unequally  fertile ;  that  which  possesses  most,  furnishes  most  hay. 
If  we  do  not  restore  to  a  meadow  the  withdrawn  elements,  its  fertility  decrease's. 
But  its  fertility  remains  unimpaired,  with  a  due  supply  of  animal  excrements,  fluid 
and  solid,  and  it  not  only  remains  the  same,  but  may  be  increased  by  a  supply  of 
mineral  substances  alone,  such  as  remain  after  the  combustion  of  ligneous  plants 
and  other  vegetables  ;  namely,  ashes.  Ashes  represent  the  whole  nourishment 
which  vegetables  receive  from  the  soil.  By  furnishing  them  in  sufficient  quantities 
to  our  meadows,  we  give  to  the  plants  growing  on  them  the  power  of  condensing 
and  absorbing  carbon  and  nitrogen  by  their  surface.  May  not  the  effect  of  the 
solid  and  fluid  excrements,  which  are  the  ashes  of  plants  and  grains,  which  have 
undergone  combustion  in  the  bodies  of  animals  and  of  man,  be  dependent  upon  the 
eame  cause  ?  Should  not  the  fertility,  resulting  from  their  application,  be  altogether 
independent  of  the  ammonia  they  contain  ?  Would  not  their  effect  be  precisely  the 
same  in  promoting  the  fertility  of  cultivated  plants,  if  we  had  evaporated  the  urine, 
and  dried  and  burned  the  solid  excrements  ?  Surely  the  ceralia  and  leguminous 
plants  which  we  cultivate  must  derive  their  carbon  and  nitrogen  from  the  same 
source  whence  the  graminea  and  leguminous  plants  of  the  meadows  obtain  them  ! 
No  doubt  can  be  entertained  of  their  capability  to  do  so. 

In  Virginia,  upon  the  lowest  calculation,  twenty-two  pounds  weight  of  nitrogen 
were  taken  on  the  average,  yearly,  from  every  morgen  of  the  wheat-fields.  This 
would  amount,  in  one  hundred  years,  to  two  thousand  two  hundred  pounds  weight. 
If  this  were  derived  from  the  soil,  every  morgen  of  it  must  have  contained  the 
equivalent  of  one  hundred  and  ten  thousand  pounds  weight  of  animal  excrements 
(assuming  the  latter,  when  dried,  at  the  temperature  of  boiling  water,  to  contain 
two  per  cent.). 

In  Hungary,  as  I  remarked  in  a  former  letter,  tobacco  and  wheat  have  been 

frown  upon  the  same  field  for  centuries,  without  any  supply  of  nitrogenized  manure. 
s  it  possible  that  the  nitrogen  essential  to,  and  entering  into,  the  composition  of 
these  crops,  could  have  been  drawn  from  the  soil  ? 

Every  year  renews  the  foliage  and  fruits  of  our  forests  of  beech,  oaks,  and  chest- 
nuts; the  leaves,  the  acorns,  the  chestnuts,  are  rich  in  nitrogen;  so  are  cocoa-nuts, 
bread-fruit,  and  other  tropical  productions.  This  nitrogen  is  not  supplied  by  man. 
Can  it,  indeed,  be  derived  from  any  other  source  than  the  atmosphere? 

In  whatever  form  the  nitrogen  supplied  to  plants  may  be  contained  in  the  atmo- 


FAMILIAR  LETTERS  ON  CHEMISTR 


sphere,  in  whatever  state  it  may  be  when  absorbed,  from  the  atmosphere  it  must 
have  been  derived.  Did  not  the  fields  of  Virginia  receive  their  nitrogen  from  the 
same  source  as  wild  plants  ? 

Is  the  supply  of  nitrogen  in  the  excrements  of  animals  quite  a  matter  of  indiffer- 
ence, or  do  we  receive  back  from  our  fields  a  quantity  of  the  elements  of  blood 
corresponding  to  this  supply? 

The  researches  of  Boussingault  have  solved  this  problem  in  the  most  satisfactory 
manner.  If,  in  his  grand  experiments,  the  manure  which  he  gave  to  his  fields  was 
in  the  same  state,  that  is,  dried  at  110°  in  a  vacuum,  as  it  was  when  analysed,  these 
fields  received,  in  sixteen  years,  thirteen  hundred  pounds  of  nitrogen. '  But  we 
know  that  by  drying  all  the  nitrogen  escapes  which  is  contained  in  solid  animal 
excrements,  as  volatile  carbonate  of  ammonia.  In  this  calculation  the  nitrogen  of 
the  urine,  which  by  decomposition  is  converted  into  carbonate  of  ammonia,  has  not 
been  included.  If  we  suppose  it  amounted  to  half  as  much  as^  that  in  the  dried 
excrements,  this  would  make  the  quantity  of  nitrogen  supplied  to  the  fields  one 
thousand  nine  hundred  and  fifty  pounds. 

In  sixteen  years,  however,  as  we  have  seen,  only  one  thousand  five  hundred  and 
seventeen  pounds  of  nitrogen  was  contained  in  their  produce  of  grain,  straw,  roots, 
etcetera — that  is,  far  less  than  was  supplied  in  the  manure;  and  in  the  same 
period,  the  same  extent  of  surface  of  good  meadow-land  (one  hectare=a  Hessian 
morgen,)  which  received  no  nitrogen  in  manure,  two  thousand  and  sixty  pounds  of 
nitrogen. 

It  is  well  known  that  in  Egypt,  from  the  deficiency  of  wood,  the  excrement  of 
animals  is  dried,  and  forms  the  principal  fuel,  and  that  the  nitrogen  from  the  soot 
of  this  excrement  was,  for  many  centuries,  imported  into  Europe  in  the  form  of  sal 
ammoniac,  until  a  method  of  manufacturing  this  substance  was  discovered  at  the 
end  of  the  last  century  by  Gravenhorst  of  Brunswick.  The  fields  in  the  Delta  of  the 
Nile  are  supplied  with  no  otber  animal  manure  than  the  ashes  of  the  burnt  excre- 
ments, and  yet  they  have  been  proverbially  fertile  from  a  period  earlier  than  the 
first  dawn  of  history,  and  that  fertility  continues  to  the  present  day  as  admirable 
as  it  was  in  the  earliest  times.  These  fields  receive,  every  year,  fronr  the  inunda- 
tion of  the  Nile,  a  new  soil,  in  its  mud  deposited  over  their  surface,  rich  in  those 
mineral  elements  which  have  been  withdrawn  by  the  crops  of  the  previous  harvest. 
The  mud  of  the  Nile  contains  as  little  nitrogen,  as  the  mud  derived  from  the  Alps 
of  Switzerland,  which  fertilises  our  fields  after  the  inundations  of  the  Rhine.  If 
this  fertilising  mud  owed  this  property  to  nitrogenised  matters;  what  enormous 
beds  of  animal  and  vegetable  exuviae  and  remains  ought  to  exist  in  the  mountains 
of  Africa,  in  heights  extending  beyond  the  limits  of  perpetual  snow,  where  no  bird, 
no  animal  finds  food,  from  the  absence  of  all  vegetation  ? 

Abundant  evidence  in  support  of  the  important  truth  we  are  discussing,  may  be 
derived  from  oth<y  well  known  facts.  Thus,  the  trade  of  Holland  in  cheese  may 
be  adduced  in  proof  and  illustration  thereof.  We  know  that  cheese  is  derived  from 
the  plants  which  serve  as  food  for  cows.  The  meadow-lands  of  Holland  derive  the 
nitrogen  of  cheese  from  the  same  source  as  with  us ;  that  is,  the  atmosphere.  The 
milch  cows  of  Holland  remain  day  and  night  on  the  grazing-grounds,  and  therefore, 
in  their  fluid  and  solid  excrements  return  directly  to  the  soil  all  the  salts  and  earthy 
elements  of  their  food :  a  very  insignificant  quantity  only  is  exported  in  the  cheese. 
The  fertility  of  these  meadows  can,  therefore,  be  as  little  impaired  as  our  own 
fields,  to  which  we  restore  all  the  elements  of  the  soil,  as  manure,  which  have  been 
withdrawn  in  the  crops.  The  only  difference  is,  in  Holland  they  remain  on  the 
field,  while  we  collect  them  at  home,  and  carry  them,  from  time  to  time  to  the  fields. 

The  nitrogen  of  the  fluid  and  solid  excrements  of  cows,  is  derived  from  the 
meadow-plants,  which  receive  it  from  the  atmosphere ;  the  nitrogen  of  the  cheese 
also  must  be  drawn  from  the  same  source.  The  meadows  of  Holland  have,  in  the 
lapse  of  centuries,  produced  millions  of  hundred  weights  of  cheese.  Thousands  of 
hundred  weights  are  annually  exported,  and  yet  the  productiveness  of  the  meadows 
is  in  no  way  diminished,  although  they  never  receive  more  nitrogen  than  they  origi- 
nally contained. 

Nothing,  then,  can  be  more  certain  than  the  fact,  that  an  exportation  of  nitrogenised 
products  does  not  exhaust  the  fertility  of  a  country ;  inasmuch  as  it  is  not  the  soil, 
but  the  atmosphere,  which  furnishes  its  vegetation  with  nitrogen.  It  follows,  con- 
sequently, that  we  cannot  increase  the  fertility  of  our  fields  by  a  supply  of  nitro- 
genised manure,  or  by  salts  of  ammonia,  but  rather  that  their  produce  increases  or 
diminishes  in  a  direct  ratio  with  the  supply  of  mineral  elements  capable  of  assimi- 
lation. The  formation  of  the  constituent  elements  of  blood — that  is,  of  the  nitro- 
genised principles  in  our  cultivated  plants— depends  upon  the  presence  of  inorganic 
matters  in  the  soil,  without  which  no  nitrogen  can  be  assimilated,  even  when  there 


45  FAMILIAR  LETTERS  ON  CHEMISTRY. 

is  a  most  abundant  supply.  The  ammonia  contained  in  animal  excrements  exer- 
cises a  favorable  effect,  inasmuch  as  it  is  accompanied  by  the  other  substances 
necessary  to  accomplish  its  transition  into  the  elements  of  blood.  If  we  supply  am- 
monia associated  with  all  the  conditions  necessary  to  its  assimilation,  it  ministers 
to  the  nourishment  of  the?  plants ;  but  if  this  artificial  supply  is  not  given,  they  can 
derive  all  the  needed  nitrogen  from  the  atmosphere — a  source,  every  loss  from  which 
is  restored  by  the  decomposition  of  the  bodies  of  dead  animals  and  the  decay  of 
plants.  Ammonia  certainly  favors  and  accelerates  the  growth  of  plants  in  all  soils, 
wherein  all  the  conditions  of  its  assimilation  are  united  ;  but  it  is  altogether  without 
effect,  as J  respects  the  production  of  the  elements  of  blood  where  any  of  these  con- 
ditions are  wanting.  We  can  suppose  that  asparagin,  the  active  constituent  of 
asparagus,  the  mucilaginous  root -o^  the  marsh-mallow,  the  nitrogenised  and  sul- 
phurous ingredients  of  mustard-seed,  and  of  all  cruciferous  plants,  may  originate  with- 
out the  aid  of  the  mineral  elements  of  the  soil.  But  if  the  principles  of  those 
vegetables,  which  serve  as  food,  could  be  generated  without  the  co-operation  of  the 
mineral  elements  of  blood,  without  potash,  soda,  phosphate  of  soda,  phosphate  of 
lime,  they  would  be  useless  to  us  and  to  herbivorous  animals  as  food ;  they  would 
not  fulfil  the  purpose  for  which  the  wisdom  of  the  Creator  has  destined  them.  In 
the  absence  of  alkalies  and  the  phosphates,  no  blood,  no  milk,  no  muscular  fibre, 
can  be  formed.  Without  phosphate  of  lime,  our  horses,  sheep,  and  cattle,  would  be 
•without  bones. 

In  the  urine  and  in  the  solid  excrements  of  animals  we  carry  ammonia,  and  con- 
sequently nitrogen,  to  our  cultivated  plants,  and  this  nitrogen  is  accompanied  by 
all  the  mineral  elements  of  food  exactly  in  the  same  proportions  in  which  both  are 
contained  in  the  plants  which  served  as  food  to  the  animals,  or,  what  is  the  same, 
in  those  proportions  in  which  both  can  serve  as  nourishment  to  a  new  generation  of 
plants,  to  which  both  are  essential. 

The  effect  of  an  artificial  supply  of  ammonia,  as  a  source  of  nitrogen,  is,  there- 
fore, precisely  analogous  to  that  of  humus  as  a  source  of  carbonic  acid — it  is 
limited  to  a  gain  of  time  ;  that  is,  it  accelerates  the  development  of  plants.  This  is 
of  great  importance,  and  should  always  be  taken  into  account  in  gardening,  espe- 
cially in  the  treatment  of  the  kitchen  garden  ;  and  as  much  as  possible  in  agriculture 
on  a  large  scale,  where  the  time  occupied  in  the  growth  of  the  plants  cultivated  is 
of  importance. 

When  we  have  exactly  ascertained  the  quantity  of  ashes  left  after  the  combustion 
of  cultivated  plants  which  have  grown  upon  all  varieties  of  soil,  and  have  obtained 
correct  analysis  of  these  ashes,  we  shall  learn  with  certainty  which  of  the  consti- 
tuent elements  of  the  plants  are  constant  and  which  are  changeable,  and  we  shall 
arrive  at  an  exact  knowledge  of  the  sum  of  all  the  ingredients  we  withdraw  from 
the  soil  in  the  different  crops. 

With  this  knowledge  the  farmer  will  be  able  to  keep  an  exact  record  of  the  pro- 
duce of  his  fields  in  harvest,  like  the  account-book  of  a  well  regulated  manufactory ; 
and  then,  by  a  simple  calculation,  he  can  determine  precisely  the  substances  he  must 
supply  to  each  field,  and  the  quantity  of  these,  in  order  to  restore  their  fertility. 
He  will  be  able  to  express,  in  pounds  weight,  how  much  of  this  or  that  element  he 
must  give  to  the  soil  in  order  to  augment  its  fertility  for  any  given  kind  of  plants. 

These  researches  and  experiments  are  the  great  desideratum  of  the  present  time. 
To  the  united  efforts  of  the  chemists  of  all  countries  we  may  confidently  look  for  a 
solution  of  these  great  questions,  and  by  the  aid  of  enlightened  agriculturists  we 
shall  arrive  at  a  rational  system  of  gardening,  horticulture,  and  agriculture,  appli- 
cable to  every  country  and  all  kinds  of  soil,  and  which  will  be  based  upon  the 
immutable  foundation  of  observed  facts  and  philosophical  inductions. 


LETTER   XVI 

MY  DEAR  SIR  : 

My  recent  .researches  into  the  constituent  ingredients  of  our  cultivated  fields 
have  led  me  to  the  conclusion  that,  of  all  the  elements  furnished  to  plants  by  the  soil 
and  ministering  to  their  nourishment,  the  phosphate  of  lime,  or,  rather,  the  phos- 
phates generally,  must  be  regarded  as  the  most  important. 

In  order  to  furnish  you  with  a  clear  idea  of  the  importance  of  the  phosphates,  it 


FAMILIAR  LETTERS  ON  CHEMISTRY.  47 

may  be  sufficient  to  remind  you  of  the  fact,  that  the  blood  of  man  and  animals, 
beside  common  salt,  always  contains  alkaline  and  earthy  phosphates.  If  we  burn 
blood  and  examine  the  ashes  which  remain,  we  find  certain  parts  of  them  soluble 
in  water,  and  others  insoluble.  The  soluble  parts  are,  common  salt  and  alkaline 
phosphates  ;  the  insoluble  consist  of  phosphate  of  lime,  phosphate  of  magnesia,  and 
oxide  of  iron. 

These  mineral  ingredients  of  the  blood — without  the  presence  of  which  in  the 
food  the  formation  of  blood  is  impossible — both  man  and  animals  derive,  either 
immediately  or  mediately,  through  other  animals,  from  vegetable  substances  used 
as  food ;  they  had  been,  constituents  of  vegetables,  they  had  been  parts  of  the  soil 
upon  which  the  vegetable  substances  were  developed. 

If  we  compare  the  amount  of  the  phosphates  in  different  vegetable  substances 
"with  each  other,  we  discover  a  great  variety,  while  there  is  scarcely  any  ashes  of 
plants  altogether  devoid  of  them,  and  those  parts  of  plants  which  experience  has 
taught  us  are  the  most  nutritious,  contain  the  largest  proportion.  To  these  belong 
all  seeds  and  grain,  especially  the  varieties  of  bread-corn,  peas,  beans,  and  lentils. 

It  is  a  most  curious  fact  that,  if  we  incinerate  grain  or  its  flour,  peas,  beans,  and 
lentils,  we  obtain  ashes,  which  are  distinguished  from  the  ashes  of  all  other  parts 
of  vegetables  by  the  absence  of  alkaline  carbonates.  The  ashes  of  these  seeds,  when 
recently  prepared,  do  not  effervesce  with  acids;  their  soluble  ingredients  consist 
solely  of  alkaline  phosphates,  the  insoluble  parts  of  phosphate  of  lime,  phosphate 
of  magnesia,  and  oxide  of  iron;  consequently,  of  the  very  same  salts  which  are 
contained  in  blood,  and  which  are  absolutely  indispensable  to  its  formation.  We 
are  thus  brought  to  the  further  indisputable  conclusion,  that  no  seed  suitable  to 
become  food  for  man  and  animals  can  be  formed  in  any  plant  without  the  presence 
and  co-operation  of  the  phosphates.  A  field,  in  which  phosphate  of  lime,  or  the 
alkaline  phosphates  form  no  part  of  the  soil,  is  totally  incapable  of  producing  grain, 
peas,  or  beans. 

An  enormous  quantity  of  these  substances,  indispensable  to  the  nourishment  of 
plants,  is  annually  withdrawn  from  the  soil  and  carried  into  great  towns,  in  the 
shape  of  flour,  cattle,  et  cetera.  It  is  certain  that  this  incessant  removal  of  the 
phosphates  must  tend  to  exhaust  the  land  and  diminish  'its  capability  of  producing 
grain.  The  fields  of  Great  Britain  are  in  a  state  of  progressive  exhaustion  from 
this  cause,  as  is  proved  by  the  rapid  extension  of  the  cultivation  of  turnips  and 
mangel-wurzel — plants  which  contain  the  least  amount  of  the  phosphates,  and  there- 
fore require  the  smallest  quantity  for  their  development.  These  roots  contain  80° 
to  92°  per  cent,  of  water.  Their  great  bulk  makes  the  amount  of  produce  fallacious, 
as  respects  their  adaptation  to  the  food  of  animals,  inasmuch  as  their  contents  of  the 
ingredients  of  the  blood — that  is,  of  substances  which  can  be  transformed  into 
flesh — stands  in  a  direct  ratio  to  their  amount  of  phosphates,  without  which  neither 
blood  nor  flesh  can  be  formed. 

Our  fields  will  become  more  and  more  deficient  in  these  essential  ingredients  of 
food,  in  all  localities  where  custom  and  habits  do  not  admit  the  collection  of  the 
fluid  and  solid  excrements  of  man,  and  their  application  to  the  purposes  of  agricul- 
ture. In  a  former  letter  I  showed  you  how  great  a  waste  of  phosphates  is 
unavoidable  in  England,  and  referred  to  the  well  known  fact,  that  the  importation 
of  bones  restored  in  a  most  admirable  manner  the  fertility  of  the  fields  exhausted 
from  this  cause.  In  the  year  1827,  the  importation  of  bones  for  manure  amounted 
to  forty  thousand  tons,  and  Huskisson  estimated  their  value  to  be  from  one  hundred 
thousand  to  two  hundred  thousand  pounds  sterling.  The  importation  is  still  greater 
at  present,  but  it  is  far  from  being  sufficient  to  supply  the  waste. 

Another  proof  of  the  efficacy  of  the  phosphates  in  restoring  fertility  to  exhausted 
land  is  afforded  by  the  use  of  the  guano — a  manure  which,  although  of-  recent 
introduction  into  England,  has  found  such  general  and  extensive  application. 

We  believe  that  the  importation  of  one  hundred  weight  of  guano  is  equivalent  to 
the  importation  of  eight  hundred  weight  of  wheat — the  hundred  weight  of  guano 
assumes,  in  a  time  which  can  be  accurately  estimated,  the  form  of  a  quantity  of 
food  corresponding  to  eight  hundred  weight  of  wheat.  The  same  estimate  is  appli- 
cable in  the  valuation  of  bones. 

If  it  were  possible  to  restore  to  the  soil  of  England  and  Scotland  the  phosphates 
which  during  the  last  fifty  years  have  been  carried  to  the  sea  by  the  Thames  and 
the  Clyde,  it  would  be  equivalent  to  manuring  with  millions  of  hundred  weights  of 
bones,  and  the  produce  of  the  land  would  increase  one-third,  or,  perhaps,  double 
itself,  in  five  or  ten  years. 

We  cannot  doubt  that  the  same  result  would  follow,  if  the  price  of  the  guano 
admitted  the  application  of  a  quantity  to  the  surface  of  the  fields,  containing  aa 
much  of  the  phosphates  as  have  been  withdrawn  from  them  in  the  same  period. 


FAMILIAR  LETTERS  ON  CHEMISTRY. 


If  a  rich  and  cheap  source  of  phosphate  of  lime  and  the  alkaline  phosphates 
were  open  to  England,  there  can  be  no  question  that  the  importation  of  foreign  corn 
might  be  altogether  dispensed  with  after  a  short  time.  For  these  materials  Eng- 
land is  at  present  dependent  upon  foreign  countries,  and  the  high  price  of  guano 
and  of  bones  prevents  their  general  application,  and  in  sufficient  quantity.  Every 
year  the  trade  in  these  substances  must  decrease,  'or  their  price  will  rise  as  the 
demand  for  them  increases. 

According  to  these  premises,  it  cannot  be  disputed  that  the  annual  expense  of 
Great  Britain  for  the  importation  of  bones  and  guano  is  equivalent  to  a  duty  on 
corn — with  this  difference  only,  that  the  amount  is  paid  to  foreigners  in  money. 

To  restore  the  disturbed  equilibrium  of  constitution  of  the  soil — to  fertilize  her 
fields — England  requires  an  enormous  supply  of  animal  excrements ;  and  it  must, 
therefore,  excite  considerable  interest  to  learn  that  she  possesses,  beneath  her  soil, 
beds  of  fossil  guano,  strata  of  animal  excrements,  in  a  state  which  will  probably 
allow  of  their  being  employed  as  a  manure  at  a  very  small  expense. 

The  coprolithes,  discovered  by  Dr.  Buckland  (a  discovery  of  the  highest  interest 
to  Geology,)  are  these  excrements;  and  it  seems  extremely  probable  that  in  these 
strata  England  possesses  the  means  of  supplying  the  place  of  recent  bones,  and, 
therefore,  the  principal  conditions  of  improving  agriculture — of  restoring  and 
exalting  the  fertility  of  her  fields. 

In  the  autumn  of  1842,  Dr.  Buckland  pointed  out  to  me  a  bed  of  coprolithes  in 
the  neighborhood  of  Clifton,  from  half  to  one  foot  thick,  enclosed  in  a  limestone 
formation,  extending  as  a  brown  stripe  in  the  rocks,,  for  miles  along  the  banks  of 
the  Severn.  The  limestone  marl,  of  Lyme  Eegis,  consists,  for  the  most  part,  of  one- 
fourth  part  of  fossil  excrements  and  bones.  The  same  are  abundant  in  the  lias  of 
Bath,  Eastern  and  Broadway  Hill,  near  Eversham.  Dr.  Buckland  mentions  beds, 
several  miles  in  extent,  the  substance  of  which  consists,  in  many  places,  of  a  fourth 
part  of  coprolithes. 

Pieces  of  the  limestone  rock  of  Clifton,  near  Bristol,  which  is  rich  in  coprolithes 
and  organic  remains,  fragments  of  bones,  teeth,  &c.,  were  subjected  to  analysis,  and 
were  found  to  contain  above  eighteen  per  cent,  of  phosphate  of  lime.  If  this  lime- 
stone is  burned,  and  brought  in  that  state  to  the  fields,  it  must  be  a  ;  perfect  sub- 
stitute for  bones,  the  efficacy  of  which,  ms  a  manure,  does  not  depend,  as  has  been 
generally  but  erroneously  supposed,  upon  the  nitrogenised  matter  which  they  con- 
tain, but  on  their  phosphate  of  lime. 

The  osseous  breccia  found  in  many  parts  of  England  deserves  especial  attention,  as 
it  is  highly  probable  that  in  a  short  time  it  will  become  an  important  article  of 
commerce.  \ 

What  a  curious  and  interesting  subject  for  contemplation  I  In  the  remains  of 
an  extinct  animal  world,  England  is  to  find  the  means  of  increasing  her  wealth  in 
agricultural  produce,  as  she  has  already  found  the  great  support  of  her  manufac- 
turing industry  in  fossil  fuel — the  preserved  matter  of  primeval  forests — the  remains 
of  a  vegetable  world.  May  this  expectation  be  realized!  and  may  her  excellent 
population  be  thus  redeemed  from  poverty  and  misery. 


THE  END. 


RESEARCHES    ON    THE 


MOTION  OF  THE 


JUICES  IN  THE  ANIMAL  BODY; 

* 

AND  THE  EFFECT  OF  EVAPORATION  IN  PLANTS. 


TOGETHER  WITH  AN  ACCOUNT  OF  THE 


ORIGIN  OF  THE  POTATO  DISEASE; 


WITH  FULL  AND  INGENIOUS  DIRECTIONS  FOR  THE  PROTECTION 
AND  ENTIRE  PREVENTION  OF  THE 


POTATO   PLANT  AGAINST  ALL  DISEASES. 
BY  JUSTUS  LIEBIG,  M.D.,  PH.D.,  F.B.S.,  M.R.I.A. 

PROFESSOR  OP  CHEMISTRY  IN  THE  UNIVERSITY  OP  GIESSEN. 

ILLUSTRATED  WITH  FIFTEEN  FINE  ENGRAVINGS. 


EDITED  FROM  THE  MANUSCRIPT  OF  THE  AUTHOR,  BY 

WILLIAM  GEEGORY,  M.  D., 

PROFESSOR  OF  CHEMISTRY  IN  THE  UNIVERSITY  OF  EDINBURQ. 


f)l)Uabd;pl)ta: 

T.  B.  PETERSON,  No.  102  CHESTNUT  STREET. 


EDITOR'S  PREFACE. 


IN  the  Editor's  Preface  to  Baron  Liebig's  "  Researches  on  the  Chemistry 
of  Food,"  in  which  the  Author  gave  the  results  of  his  investigation  into  the 
constituents  of  the  juice  of  the  flesh,  I  mentioned  that  Baron  Liebig  had 
been  led  to  study  the  subject  of  Endosmosis  experimentally.  The  results 
of  this  investigation  are  contained  in  the  following  pages ;  and  the  reader 
will,  I  trust,  be  satisfied  that  the  motions  of  the  animal  juices  depend  on 
something  more  than  mere  Endosmosis  or  Exosmosis,  and  that  the  pressure 
of  the  atmosphere,  as  well  as  its  hygrometric  state,  by  influencing  the 
transpiration  from  the  skin  and  lungs,  are  essentially  concerned  in  pro- 
ducing these  motions.  At  the  same  time,  the  present  work  is  to  be  regarded, 
not  as  exhausting  the  subject,  but,  on  the  contrary,  as  only  pointing  out 
the  direction  in  which  inquiry  is  likely  to  lead  to  the  most  valuable 
results. 

While  it  is  proved  that  the  mechanical  causes  of  pressure  and  evapora- 
tion, and  the  chemical  composition  of  the  fluids  and  membranes,  have  a 
more  direct,  constant,  and  essential  influence  on  the  motion  of  the  animal 
fluids,  and,  consequently,  on  the  state  of  the  health,  than  has  been  usually 
supposed,  it  is  evident  that  very  much  remains  to  be  done  in  tracing  that 
influence  under  the  ever  varying  circumstances  of  the  animal  body,  and 
in  applying  the  knowledge  thus  acquired  to  the  purposes  of  hygiene 
and  therapeutics.  But  it  is  equally  obvious,  that  the  above-mentioned 
mechanical  and  chemical  causes  are  not  alone  sufficient  to  explain  the 
phenomena  of  animal  life,  since  they  are  present  equally  in  a  dead  and  in  a 
living  body ;  so  that  while  every  advance  in  physiology  enables  us  to  explain 
more  facts  on  chemical  and  mechanical  principles,  something  always 

(3) 


iv  EDITOR'S  PREFACE. 

remains,  which,  for  the  present,  is  beyond  our  reach,  and  which  may  for- 
ever remain  so.  However  this  may  be,  the  facts  established  in  this  and 
in  the  preceding  work  of  the  Author  have  very  materially  extended  the 
application  of  the  well-known  laws  of  physics  and  of  chemistry  to  physio- 
logy, and  have  also  furnished  a  number  of  the  most  beautiful  instances  of 
that  infinitely  wise,  but  exquisitely  simple  adaptation  of  means  to  ends, 
which  characterizes  all  the  works  of  the  omnipotent  Creator ;  but  which  is 
no  where  more  admirably  displayed,  than  in  the  arrangements,  imperfectly 
known  as  they  hitherto  are,  by  which  life  is  maintained. 

In  connection  with  the  Author's  remarks  on  the  effects  of  evaporation 
in  plants,  and  the  consequences  of  its  suppression,  and  with  his  opinions 
as  to  the  origin  of  the  potato  disease,  I  beg  to  refer  the  reader  to  the 
Appendix  for  a  very  ingenious  and  apparently  well  founded  plan  for  the 
protection  of  the  potato  plant  against  the  terrible  scourge  under  which  it 
has  lately  suffered.  The  views  of  Dr.  Klotzsch,  the  author  of  this  plan, 
as  to  the  nature  of  the  disease,  coincide  remarkably  with  those  of  Baron 
Liebig,  as  explained  in  the  present  work. 

WILLIAM  GREGORY. 

EDINBURGH,  3d  March,  1852. 


PEEFACE. 


THE  present  little  work  contains  a  series  of  experiments  the  object  of 
which  is  to  ascertain  the  law  according  to  which  the  mixture  of  two  liquids, 
separated  by  a  membrane,  takes  place.  The  reader  will,  I  trust,  perceive 
in  these  researches  an  effort  to  attain,  experimentally,  to  a  more  exact 
expression  of  the  conditions  under  which  the  apparatus  of  the  circulation 
acquires  all  the  properties  of  an  apparatus  of  absorption. 

In  the  course  of  this  investigation,  the  more  intimate  study  of  the 
phenomena  of  Endosmosis  impressed  on  me  the  conviction  that,  in  the 
organism  of  many  classes  of  animals,  causes  of  the  motion  of  the  juices 
were  in  operation,  far  more  powerful  than  that  to  which  the  name  of  Endos- 
mosis has  been  given. 

The  passage  of  the  digested  food  through  the  membranes  of  the  intes- 
tinal canal,  and  its  entrance  into  the  blood ;  the  passage  of  the  nutrient 
fluid  outwards  from  the  blood  vessels,  and  its  motion  towards  the  parts 
where  its  constituents  acquire  vital  properties, — these  two  fundamental 
phenomena  of  organic  life  cannot  be  explained  by  a  simple  law  of  mixture. 

The  Experiments  described  in  the  following  pages  will,  perhaps,  be  found 
to  justify  the  conviction  that  these  organic  movements  depend  on  the 
transpiration  and  on  the  atmospheric  pressure. 

The  importance  of  the  transpiration  for  the  normal  vital  process  has, 
indeed,  been  acknowledged  by  physicians  ever  since  Medicine  had  an 
existence ;  but  the  law  of  the  dependance  of  the  state  of  health  on  the 
quality  of  the  atmosphere,  on  its  barometric  pressure,  and  its  hygrometric 
condition,  has  been  hitherto  but  little  investigated. 

By  the  researches  contained  in  my  examination  of  the  constituents  of 
the  juice  of  flesh,  as  well  as  by  those  described  in  the  present  work,  the 
completion  of  the  second  part  of  my  Animal  Chemistry  has  been  delayed ; 
but  I  did  not  consider  myself  justified  in  continuing  that  work  until  I  had 
examined  the  questions  suggested  by,  and  connected  with  those  researches, 

DR.  JUSTUS  LIEBIG. 


,  February,  1852. 

(5) 


CONTENTS. 


PAQ1 

On  the  phenomena  accompanying  the  mixture  of  two  liquids  separated  by  a  mem- 
brane    9 

Relation  of  porous  bodies  to  water  and  other  liquids 9 

The  moistening  of  porous  bodies  depends  on  capillary  attraction 10 

Pressure  required  to  cause  liquids  to  pass  through  membranes 11 

The  pressure  varies  with  different  liquids •  •  •  • 11 

The  absorbent  power  of  the  membrane  has  a  share  in  the  effect 11 

Action  of  brine,  oil,  alcohol,  &c.,  on  moist  membranes 12 

Cause  of  the  shrivelling  of  membranes  when  strewed  with  salt 13 

Animal  tissues  are  permeable  to  all  liquids 14 

Saline  solutions,  alcohol,  &c.,  mix  with  water  through  membranes 15 

Change  of  volume  when  two  dissimilar  liquids  mix  through  a  membrane ;  Endosmosis  15 

This  change  of  volume  does  not  depend  alone  on  the  different  densities 15 

Phenomena  of  the  mixture  of  two  liquids  through  a  membrane 16 

The  mixture  is  the  result  of  chemical  attraction 18 

Chemical  attraction  is  every  where  active 19 

Examples. — Crystallization 19 

Action  of  solids  on  dissolved  matters 19 

Lawa  of  the  mixture  of  two  dissimilar  liquids 21 

Effect  of  the  interposition  of  a  membrane 22 

The  change  of  volume  in  two  liquids  which  mix  through  a  membrane  is  the  result 

of  chemical  affinity  modifying  capillary  attraction 23 

Effect  of  evaporation  on  liquids  confined  by  membranes 24 

Views  of  MAGNUS  on  Endosmosis 24 

Remarks  on  his  theory 24 

The  nature  of  the  membrane  has  an  important  influence 25 

Unequal  attraction  of  membranes  for  different  liquids 2§ 

The  action  of  two  liquids,  separated  by  a  membrane,  is  equivalent  to  pressure,  un- 
equal on  opposite  sides 27 

Causes  which  influence  the  mixture  of  two  liquids  separated  by  a  membrane 29 

These  causes  produce,  in  the  animal  body,  absorption  of  the  fluids  of  the  intestines 

into  the  blood 30 

Effects  of  drinking  water  and  saline  solutions  of  different  strengths 30 

Influence  of  the  cutaneous  evaporation  on  the  motion  of  the  animal  juices 31 

(7) 


8  CONTENTS. 


PAGE 

Experiments 32 

Influence  of  the  atmospheric  pressure 33 

Water  passes  through  membranes  more  easily  than  air  does 34 

Experiments  on  evaporation  through  membranes 34 

Importance  of  the  cutaneous  transpiration 35 

By  it  the  fluids  acquire  a  motion  towards  the  skin  and  lungs 35 

Effects  of  dry  and  moist  air,  and  of  elevation,  on  the  health 35 

Causes  of  the  efflux  of  sweat 36 

Fishes  die  in  air,  because  the  due  distribution  of  the  fluids  is  prevented 36 

Experiments  of  HALES  on  the  motion  of  the  sap  in  plants 36 

This  motion  is  caused  by  evaporation 37 

Force  with  which  the  sap  rises 37 

The  atmospheric  pressure  is  the  active  force 38 

The  sap  absorbs  gases 38 

The  evaporation  supplies  food  to  the  plant 38 

Influence  of  suppressed  evaporation  on  hop  vines 39 

Observations  of  HALES  on  the  blight  in  hops,  &c 39 

Fire-blasts  in  hops 39 

HALES  recognized  the  influence  of  evaporation  on  the  life  of  plants 39 

The  origin  of  the  potato  disease  is  probably  similar  to  that  of  the  blight  in  hops. . .  40 

The  disease  long  known 40 

It  is  due,  not  to  a  degeneration  of  the  plant,  but  to  a  combination  of  external  cir- 
cumstances    40 

It  is  connected  with  the  weather,  and  particularly  with  the  temperature  and  hygro- 

metric  state  of  the  atmosphere 41 

The  life  of  plants  is  dependent  chiefly  on  four  external  causes 41 

Only  one  of  which,  namely,  the  quality  of  the  soil,  is  in  the  power  of  the  agriculturist  41 

Effects  of  suppressed  evaporation 41 

The  fungi  and  putrefaction  follow  the  death  of  the  plant 41 

Observations  of  HALES  on  the  rise  of  the  spring  sap  in  perennial  plants 41 

Views  of  DUTROCHET  . . .  t 42 

Objections  to  these  views 42 

The  cause  of  the  rise  of  the  sap  is  transient,  and  depends  on  external  influences. . .  42 

It  exists,  not  merely  in  the  spongioles,  but  in  all  parts  of  the  plant 42 

Experiments  of  HALES 43 

His  conclusions 43 

Gas  is  given  off  by  the  sap 44 

The  rise  may  therefore  be  due  to  the  disengagement  of  gas 44 

The  gas  is  probably  carbonic  acid 44 

APPENDIX 

Account  of  a  plan  proposed  by  Dr.  KLOTZSCH,  of  Berlin,  protecting  potato  plants 

from  disease 45 

This  plan  published  by  authority  of  the  Minister  of  the  Interior  of  Prussia,  on  the 

favorable  report  of  the  President  of  the  College  of  Kural  Economy  at  Berlin ....  47 

Conditions  on  which  the  reward,  claimed  for  his  plan,  if  found  effectual,  by  Dr. 

KLOTZSCH,  has  been  granted , 47 


ON 

THE  PHENOMENA 

ACCOMPANYING 

THE  MIXTURE  OF  TWO  LIQUIDS 

SEPARATED    BY 

A  MEMBRANE. 


THE  constituents  of  the  food,  which  have  assumed  a  soluble  form  in  the  alimentary 
canal,  are  thereby  endowed  with  the  property  of  yielding  to  the  influence  of  every 
cause  which,  in  acting  on  them,  tends  to  change  their  place  or  the  position  which 
they  occupy.*  They  are  conveyed  into  the  blood  vessels,  and  from  thence  are 
distributed  to  all  parts  of  the  body. 

The  movement  and  distribution  of  these  fluids,  and  of  all  the  substances  dissolved 
in  them,  exclusive  of  the  mechanical  cause  of  the  contraction  of  the  heart,  by 
which  the  circulation  of  the  blood  is  effected,  depend,  1,  on  the  permeability  of  the 
walls  of  all  vessels  to  these  fluids  ;  2,  on  the  pressure  of  the  atmosphere  ;  and  3, 
on  the  chemical  attraction  which  the  various  fluids  of  the  body  exert  on  each  other.t 
The  motion  of  all  fluids  in  the  body  is  effected  by  means  of  water :  and  all  parts 
of  the  animal  system  contain,  in  the  normal  state,  a  certain  amount  of  water. 

Animal  membranes,  tendons,  muscular  fibres,  cartilaginous  ligaments,  the  yellow 
ligaments  of  the  vertebral  column,  the  cornea,  transparent  and  opaque,  &c.,  all 
contain,  in  the  fresh  state,  more  than  half  their  weight  of  water,  which  they  lose, 
more  or  less  completely,  in  dry  air.J 

On  the  presence  of  this  water  depend  several  of  their  physical  properties. 
The  fresh,  opaque,  milk-white  cartilagesof  the  ear  become,  when  dried,  translucent, 
and  acquire  a  reddish  yellow  color.  Tendons,  when  fresh,  are  in  a  high  degree 
flexible  and  elastic  and  possess  a  silky  lustre,  which  they  lose  when  dried.  By  the 
same  loss  of  water  they  become,  further,  hard,  horny,  and  translucent,  and  when 
bent,  split  into  whitish  bundles  of  fibres.  The  sclerotic  coat  is  milk-white  when 
fresh,  and  becomes  transparent  by  desiccation. 

When  these  substances,  after  having  lost,  by  drying,  a  part  of  the  properties 
which  they  possess  in  the  fresh  state,  are  again  placed  in  contact  with  pure  water, 
they  take  up,  in  24  hours,  the  whole  original  amount  of  water,  and  recover  per- 
fectly those  properties  which  they  had  lost.  The  opaque  cornea,  or  sclerotic  coat, 
which  had  become  transparent  by  desiccation,  again  becomes  milk-white,  while  the 
transparent  cornea,  which  had  been  rendered  opaque  by  drying,  now  becomes 
again  transparent.  The  tendons,  which,  when  dried,  had  become  horny,  hard, 
and  translucent,  now  again  become  flexible  and  elastic,  and  recover  their  silky 

*  The  food  becomes  soluble,  and  the  fluids  of  the  body  are  sent  to  all  parts. 
tGeneral  causes  of  their  moti>n.  J  Relation  of  animal  tissues  to  water. 

3  (9) 


10  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

lustre.  The  fibrine  and  the  cartilages  of  the  ear,  which  desiccation  had  rendered 
horny  and  transparent,  again  become  milk-white  and  elastic. 

The  power  which  the  solids  of  the  animal  body  possess  of  taking  up  water 
into  their  substance,  and  of  being  penetrable  to  water,  extends  to  all  fluids  allied  to 
water,  that  is  miscible  with  it.*  In  the  dried  state,  the  animal  solids  take  up  fluids 
of  the  most  diverse  natures,  such  as  fatty  and  volatile  oils,  ether,  bisulphuret  of 
carbon,  &c.  This  permeability  to  fluids  is  possessed  by  animal  tissues  in  common 
with  all  porous  bodies ;  and  no  doubt  can  be  entertained,  that  this  property  is 
determined  by  the  same  cause  which  produces  the  ascent  of  fluids  in  narrow  tubes, 
or  in  the  pores  of  a  sponge  ;  phenomena,  which  we  are  accustomed  to  include 
under  the  name  of  capillary  action. 

One  condition,  essential  to  the  permeability  of  porous  bodies  for  fluids  (or  their 
power  of  absorption),  is  their  capability  of  being  moistened ;  or  the  attraction 
which  the  particles  of  the  fluid  and  the  walls  of  the  pores  or  tubes  have  towards 
each  other.t  A  second  condition  is  the  attraction  which  one  particle  of  the  fluid 
has  to  another.  We  have  no  means  of  estimating  the  absolute  size  of  the  particles 
or  molecules  of  a  fluid,  such  as  water,  but  they  are  certainly  infinitely  smaller  than 
the  measurable  diameter  of  a  tube,  or  of  the  pores  of  a  porous  body.  It  is  obvious, 
therefore,  that  in  the  interior  of  a  capillary  tube  or  pore,  filled  with  a  fluid,  only  a 
certain  number  of  the  fluid  molecules  are  in  contact  with  the  walls  of  the  tube,  and 
attracted  by  them  ;  while  in  the  middle  of  the  tube,  and  from  thence  towards  its 
parietes,  fluid  molecules  must  exist  which  only  retain  their  place  in  virtue  of  the 
attraction  which  the  molecules,  attracted  .by  the  parietes,  exert  on  those  not  so 
attracted ;  that  is,  by  the  cohesive  attraction  of  the  fluid. 

Liquids  flow  out  of  capillary  tubes,  which  are  filled  with  them,  only  when  some 
other  force  or  cause  acts,  because  capillary  attraction  cannot  produce  motion 
beyond  the  limits  of  the  solid  body  which  determines  the  capillary  action. 

The  penetration  of  a  fluid  into  the  pores  of  a  porous  body,  is  the  result  of 
capillary  attraction ;  its  expulsion  can  be  affected  by  a  mechanical  pressure ;  and 
may  be  accelerated  by  increasing  this  pressure,  and  by  all  such  causes  as  diminish 
the  mutual  attraction  of  the  fluid  molecules,  or  the  attraction  of  the  walls  of  the 
pores  for  those  molecules.  The  condition  most  favorable  to  the  passage  of  a 
fluid  through  the  pores  of  a  porous  substance  under  pressure,  is  when  one  fluid 
molecule  can  be  displaced  so  as  to  glide  away  over  another. 

The  slightest  pressure  suffices  to  expel  the  displaceable  particles  of  water  from 
a  sponge ;  a  higher  pressure  is  required  to  express  the  same  fluid  from  bibulous 
paper ;  and  a  pressure  much  higher  still  is  necessary  in  order  to  cause  water  to  flow 
out  of  moist  wood.^;  We  may  form  some  idea  of  the  force  with  which  porous  organic 
substances,  such  as  dry  wood,  absorb  and  retain  water,  if  we  remember,  that  by 
inserting  of  wedges  of  dry  wood  in  proper  cuts,  and  subsequently  moistening  them, 
rocks  may  be  split  and  fractured. 

When  we  compare  with  the  properties  just  enumerated,  which  belong  to  all 
porous  bodies,  those  properties  which  are  observed  in  animal  substances  under  the 
same  circumstances,  it  appears  plainly  that  these  animal  substances  have  pores  in 
certain  directions  ;§  although  these  openings  are  so  minute  that  they  are  not,  in  the 
case  of  most  tissues,  perceptible,  even  with  the  aid  of  the  best  microscopes. 

It  has  been  mentioned  that  tendons,  ligaments,  cartilages,  &c.,  contain,  in  the  fresh 
state,  a  certain  amount  of  water,  which,  according  to  all  experiments  made  on  the 
subject,  is  invariable ;  and  that  several  of  their  properties  depend  on  the  presence 
of  this  water. ||  (CHEVREUL.)  When  these  substances,  wrapped  in  bibulous  paper, 
are  subjected  to  a  powerful  pressure,  a  certain  proportion  of  this  water  is  expelled. 
Fresh  and  flexible  vessels  lose,  in  this  way,  37.6  per  cent.,  and  the  yellow  liga- 
ments of  the  vertebrae  lose  35  per  cent,  of  water.  This  property,  namely,  that  of 
losing  water  under  pressure,  is  only  found  in  porous  substances.  It  is  obvious  that 
by  pressure,  that  is,  by  diminution  of  the  size  of  the  pores,  only  that  portion  of 

•The  tissues  absorb  other  fluids.  fThe  moistening  of  porous  bodies. 

{Prodigious  force  with  which  porous  bodies  absorb  water. 

i  Animal  tissues  are  porous. 

lAmount  of  water  expelled  by  pressure  from  tissues. 


ABSORBENT  POWER   OF   MEMBRANES.  11 

water  can  be  pressed  out  which  is  not  retained  by  chemical  attraction.*  It  is  in 
the  highest  degree  worthy  of  notice,  that  this  water,  not  chemically  combined,  seems 
to  have  the  greatest  share  in  the  properties  which  these  animal  substances  possess 
in  the  fresh  state,  for  the  pressed  tendons  and  yellow  ligaments  become  transparent ; 
the  former  lose  their  flexibilty,  the  latter  their  elasticity  ;  and  if  laid  in  water,  they 
recover  these  properties  perfectly.  In  the  pores  of  a  porous  substance,  the  fluid 
molecules  are  retained  by  two  kinds  of  attraction,  namely,  by  the  affinity  which  is 
exerted  between  the  walls  of  the  pores  and  the  molecules  of  the  fluid,  and  by  the 
cohesion  which  acts  between  the  molecules  of  the  fluid  itself.  It  would  appear  as 
if  the  molecules  of  water  were  thus  brought  into  different  states,  and  this  seems  to 
be  the  cause  of  the  differences  observed  in  the  properties  of  these  animal  substances 
when  they  contain  different  proportions  of  water.  fig.  i. 

t  If  the  wide  opening  of  the  tube,  Fig.  1,  be  tied  over  with  a  por- 
tion of  bladder,  and  water  poured  into  the  wide  part  of  the  tube,  as 
far  as  the  mark  «,  we  shall  find  that,  when  mercury  is  poured  into 
the  upright  narrow  part  of  the  tube,  to  a  certain  height,  the  whole 
external  surface  of  the  bladder  becomes  covered  with  minnte  drops, 
which,  if  the  column  of  mercury  be  made  a  few  lines  higher,  unite, 
so  as  to  form  large  drops.  These  continue  to  flow  out  uninter- 
ruptedly, if  mprcury  be  added,  so  as  to  keep  the  column  at  the  same 
height,  till  at  last  the  wide  part  of  the  tube  is  emptied  of  water  and 
filled  with  mercury. 

Solution  of  salt,  fat  oil,  alcohol,  &c.,  behave  exactly  as  water  does ; 
under  a  certain  pressure  these  fluids  pass  through  an  animal  mem- 
brane, just  as  water  does  through  a  paper  filter. 

The  pressure  required  to  cause  these  liquids  to  flow  through  the 
pores  of  animal  textures  depends  on  the  thickness  of  the  membrane, 
as  well  as  on  the  chemical  nature  of  the  different  liquids. 

Through  ox-bladder,  y^th  of  a  line  (TJ^th  of  an  inch)  thick, 
water  flows  under  a  pressure  of  12  inches  of  mercury.^  A  saturated 
solution  of  sea  salt  requires  from  18  to  20  inches  ;  and  oil  (mar- 
row oil)  only  flows  out  under  a  pressure  of  34  inches  of  mercury. 

When  the  membrane  used  is  the  peritoneum  of  the  ox,  ^th  of  a  line,  (^J-^th  of 
an  inch)  in  thickness,  water  is  forced  through  it  by  8  to  10  inches,  brine  by  12  to 
16  inches,  oil  by  22  to  24  inches,  and  alcohol  by  36  to  40  inches  of  mercury. 

The  same  membrane  from  the  calf,  gjgth  of  a  line  (y^^d  of  an  inch)  in  thick- 
ness, allows  water  to  pass  through  under  the  pressure  of  a  column  of  water  4  inches 
high  ;  brine  passes  under  a  pressure  of  8  to  10  inches  of  brine,  and  oil  under  a 
pressure  of  3  inches  of  mercury. 

In  making  experiments  of  this  nature,  we  observe  that,  after  they  have  continued 
for  some  time,  the  pressure  required  to  force  the  liquid  through  the  membrane  does 
not  continue  equal.  If  during  the  first  6  hours  a  pressure  of  12  inches  of  mer- 
cury were  necessary,  we  often  find  that  after  24  or  36  hours,  8,  or  even  6  inches 
will  suffice  to  produce  the  same  effect,  obviously  because  by  long-continued  con- 
tact with  water,  the  membrane  undergoes  an  alteration,  in  consequence  of  which 
the  pores  are  widened. 

From  these  experiments  it  appears,  that  the  power  of  a  liquid  to  filter  through 
an  animal  membrane  bears  no  relation  to  the  mobility  of  its  particles  ;§  for  under  a 
pressure  which  causes  water,  brine,  or  oil  to  pass  through,  the  far  more  mobile 
alcohol  does  not  pass. 

The  capacity  of  the  animal  membrane  for  being  moistened  by,  and  its  power  of 
absorbing,  the  liquid,  have  a  certain  share  in  producing  the  result  of  its  filtration 
through  the  membrane. || 

The  following  table  will  show  this  fact : 

*  The  portion  of  water  not  chemically  combined,  has  the  greatest  share  in  the  properties  of 
the  tissues. 

t  Pressure  required  to  cause  water  and  any  other  liquids  to  pass  through  membranes. 
t  The  pressure  varies  with  different  liquids. 

$  The  passage  of  liquids  through  membranes  not  in  proportion  to  their  fluidity. 
H  The  absorbent  power  of  the  membrane  for  the  liquid  has  a  share  in  the  effect. 


12  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

100  parts,  by  weight,  of  dry  ox-bladder,  take  up  in  24  hours,  — 

of  pure  water    ..........................  268  volumes 

„  saturated  solution  of  sea  salt  (brine)    .  .  .  133        „ 
,,  alcohol  of  84  per  cent  .................    38        „ 

„  oil  of  marrow*   .......................     17         „ 

100  parts,  by  weight,  of  ox-bladder,  take  up  in  48  hours,  — 


of  pure  water 
of  a  mixture  c 
»            »> 
»            »> 
»>            >» 
>»            » 

310  pai 

rts  by  weight 
» 
» 

p 
» 
» 

>f  £  water  anc 
» 

H 

i    alcohol 

*                »> 

I  ^  brine 
A  

....  219 
.  .  .  .    235 

^  

288 

A  . 

60 

181 

j  . 

,.  290 

100  parts  of  dry  pig's  bladder  take  up  in  24  hours,— 

of  pure  water  ...........................  356  volumes 

„  brine    ................................  159       „ 

„  oil  of  marrow  ........................    14       „ 

From  these  experiments  it  appears  that  the  absorptive  power  of  animal  mem- 
branes for  different  liquids  is  very  different.  Of  all  liquids,  pure  water  is  taken 
up  in  the  largest  quantity  ;  and  the  absorptive  power  for  solution  of  salt  diminishes 
in  a  certain  ratio  as  the  proportion  .  of  salt  increases.  A  similar  relation  holds 
between  the  membranes  and  alcohol  ;  for  a  mixture  of  alcohol  and  water  is  taken 
up  more  abundantly  the  less  alcohol  it  contains.1 

(')  In  regard  to  this  property,  membranes  differ  in  no  respect  from  other  animal 
textures,  as  was  long  ago  proved  by  Chevreul.  This  distinguished  philosopher  found 
that  the  following  substances  absorbed,  in  24  hours,  of  water,  brine,  and  oil,  — 

Cubic 

Centimetres       C.  C.       C.  C. 
Water.  Brine.         Oil. 

100  grammes  of  cartilage  of  the  ear  .......     231            125  — 

100           „           tendons    .................     178            114  8.6 

100           „           yellow  ligaments  of  spine  .  .     148              30  7.2 

100           „           cornea  ...............  '...     461            370  9.1 

100           „           cartilaginous  ligaments  ....     319             —  3.2 

100          „  dry  fibrine  absorbed  .  .....     301  of  water  and  148 

of  alcohol  of  69  per 
cent.     (Liebig.) 

100          „  „  „         .......     184  parts  by  weight 

or  154  by  volume  of 
brine  » 

Animal  membranes  do  not  acquire,  by  absorbing  alcohol  or  oil,  those  properties 
which  they  exhibit  when  saturated  with  water.t  A  dried  bladder  continues 
hard  and  brittle  in  alcohol  and  oil  ;  its  flexibility  is  in  no  degree  increased  by 
absorbing  these  liquids.  When  tendons,  ligaments  (CHEVREUL,)  the  yellow  liga- 
ments of  the  spine,  or  bladder,  saturated  with  oil,  are  placed  in  water,  the  oil  is 
completely  expelled,  and  they  take  up  as  much  water  as  if  they  had  not  previously 
been  in  contact  with  oil. 

It  has  been  mentioned,  that  100  parts  of  animal  membrane  (dry  ox-bladder) 
absorb  in  24  hours  268,  in  48  hours  310  volumes  of  water,  and  only  133  of 
saturated  solution  of  salt.  It  follows,  of  course,  that  when  the  bladder,  saturated 
with  water  by  48  hours'  contact,  z  id  well  dried  in  bibulous  paper,  without  pressure, 
to  remove  superfluous  water,  is  trevved  with  salt,  there  is  formed,  at  all  points 
where  salt  comes  in  contact  with  be  water  filling  the  open  pores,  a  saturate  d  solu- 

*  Absorption  of  different  liqvids. 

+  Effects  of  oil,  salt,  &c.,  on    aerr  lirar      when  dry,  and  when  in  the  moist  state. 


MEMBRANES  SATURATED  WITH  WATER.  13 

tion  of  salt,  the  salt  contained  in  which  diffuses  itself  equally  in  the  water  of  the 
bladder.  Of  the  310  volumes  of  water  which  become  thus  saturated  with  salt, 
only  133  volumes  are  retained  in  the  bladder;  and  in  consequence  of  this  diminu- 
tion of  the  absorbent  power  of  the  bladder  for  the  brine,  177  volumes  of  liquid  are 
expelled,  and  run  off  in  drops  from  the  surface  of  the  bladder. 

Membranes,  fibrine,  or  a  mass  of  flesh,  behave  exactly  in  a  similar  manner  when 
in  contact  with  alcohol.  If  placed  in  alcohol  in  the  fresh  state,  that  is,  when  they 
?re  thoroughly  charged  with  water,  there  are  formed,  at  all  points  where  water  and 
alcohol  meet,  mixtures  of  the  two,  and  as, the  animal  texture  absorbs  much  less  of 
an  alcoholic  mixture  than  of  pure  water,  more  water  is,  of  course,  expelled,  than 
alcohol  taken  up. 

9-17  grammes  of  bladder,  fresh,  that  is  saturated  with  water  (in  which  are  con- 
tained 6'95  grammes  of  water,  and  2-22  of  dry  substance,)  when  placed  in  40 
cubic  centimetres  of  alcohol,  weigh,  at  the  end  of  24  hours,  4'73  grammes,  and 
have,  consequently,  lost  4'44  grammes.*  In  the  4-73  grammes  which  remain,  are 
2-22  grammes  of  dry  bladder,  and,  of  course,  2-51  grammes  of  liquid.  If  we 
assume  that  this  liquid  has  the  same  composition  as  the  surrounding  mixture 
(which  is  found  to  contain  84  parts  of  alcohol  to  16  of  water,)  it  will  consist  of 
2-11  grammes  of  alcohol  and  0-40  of  water;  and  consequently,  of  the  6-95  gram- 
mes of  water  originally  present,  6-45  grammes  have  been  expelled,  and  replaced 
by  2-11  grammes  of  alcohol.  For  1  volume  of  alcohol,  therefore,  retained  by  the 
bladder,  rather  more  than  3  volumes  of  water  have  been  expelled  from  it. 

t  Since,  in  this  case,  so  much  more  water  is  expelled  than  is  taken  up  of  alcohol, 
the  first  result  is  a  shrinking  of  the  animal  substance^1) 

If  the  bladder  could  take  up  or  absorb  equal  volumes  of  brine  and  water,  or  of 
alcohol  and  water,  then  when  the  fresh  bladder  was  strewed  with  salt,  or  laid  in 
alcohol,  the  volume  of  the  absorbed  liquid  would  be  unaltered,  and  an  equal  volume 
of  saline  solution,  or  of  diluted  alcohol,  would  be  retained  by  the  animal  tissue. 
But  since  the  absorbent  power  of  the  tissue  for  water  is  diminished  by  the  addition 
of  salt,  or  of  alcohol,  it  follows  plainly,  that  a  certain  quantity  of  water  must  be 
expelled  as  soon  as  its  character  is  changed  by  the  addition  of  one  of  these 
substances. 

The  relation  of  bladder,  fibrine,  and  other  animal  substances,  when  saturated 
with  water,  to  alcohol  and  brine,  proves,  that  the  shrinking  (diminution  of  volume') 
of  these  tissues  does  not  depend  on  a  simple  abstraction  of  water  in  virtue  of  the 
affinity  of  alcohol  and  of  salt  for  that  liquid  ;  for  it  is  quite  certain  that  the  attrac- 
tion of  alcohol  to  water,  and  that  of  water  to  alcohol,  are  respectively  equal.J  The 
attraction  of  the  water  within  the  tissue  for  the  alcohol  without,  is  just  as  strong  as 
the  power  of  the  alcohol  without  to  combine  with  the  water  within.  Less  alcohol 
is  taken  up,  and  more  water  given  out,  because  the  animal  tissue  has  less  attraction 
for  the  mixture  of  alcohol  and  water  than  for  pure  water  alone.  The  alcohol  with- 
out becomes  diluted,  the  water  within  becomes  mixed  with  a  certain  proportion  of 
alcohol,  and  this  exchange  is  only  arrested  when  the  attraction  of  the  water  for  the 
animal  tissue,  and  its  attraction  for  alcohol,  come  to  counterpoise  each  other. 

If  we  regard  a  piece  of  skin,  or  bladder,  or  fibrine  as  formed  of  a  system  of  capil 
lary  tubes,  the  pores  or  minute  tubes  are,  in  the  fresh  state,  filled  with  a  watery 
liquid,  which  is  prevented  from  flowing  out  by  capillary  attraction. 

But  the  liquid  contained  in  these  capillary  tubes  flows  out  of  them  as  soon  as  its 
composition  is  altered  by  the  addition  of  salt,  alcohol,  or  other  bodies. 

(})  Fibrine  and  other  animal  matters  exhibit  results  quite  similar  to  those  obtained 
with  bladder.  26'02  grammes  of  fibrine  saturated  with  water  (containing  6*48  grammes 
of  dry  fibrine  and  19'54  of  water)  were  reduced,  in  45  grammes  of  absolute  alcohol,  to 
16-12  grammes,  losing,  therefore,  9'90  grammes.  Admitting  the  absorbed  liquid  to  have 
the  composition  of  the  unabsorbed  residue  (70  per  cent,  of  alcohol,)  it  appears,  that  for 
1  volume  of  alcohol  absorbed  by  fibrine  rather  more  than  2£  volumes  of  water  are 
separated. 

*  Amount  of  water  expelled  from  bladder  by  alcohol. 

tMoist  membranes  shrink  when  strewed  with  salt,  or  placed  in  alcohol. 

J  The  cause  of  this  is  the  less  affinity  of  the  tissue  for  alcohol,  &c.,  than  for  water. 


14  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

If  we  lay  together,  one  over  the  other,  two  portions  of  bladder,  saturated  with 
solution  of  salt  of  sp.  g.  1-204,  and  over  the  upper  one  another  piece  of  bladder  of 
equal  size,  saturated  with  water,  and  if  we  allow  them  to  remain  thus,  without 
pressure,  we  find,  after  some  minutes,  when  the  two  pieces  saturated  with  solution 
of  salt  are  separated,  that  drops  of  saline  solution  appear  between  them,  of  which 
no  trace  could  previously  be  perceived.  If  the  piece  of  bladder  saturated  with  water 
contained  5  volumes  of  water,  and  the  next  piece  3  volumes  of  saline  solufion, 
there  must  be  produced,  by  the  mixture  of  both,  8  volumes  of  diluted  saline  solufion, 
of  which  each  piece  of  bladder  must  contain  one  half,  or  4  volumes,  if  the  absorbent 
power  of  the  portion  saturated  with  the  original  saline  solution  were  increased  by 
the  addition  of  water  in  the  same  ratio  as  the  absorbent  power  of  the  portion  satu- 
rated with  water  was  diminished  by  the  addition  of  salt.  The  saline  liquid  would 
have  given  up  1^  volume  of  saline  solution  to  the  other,  and  would  have  received 
from  it  2£  volumes  of  water.  In  this  case,  the  mixture  in  the  two  upper  pieces 
of  bladder  would  occupy  the  same  space  which  its  constituents,  water  and  saline 
solution,  occupied  in  each  singly.  But  the  efflux  of  the  liquid  towards  the  third  or 
lowest  piece  of  bladder  saturated  with  saline  solution,  proves,  that  the  two  uj>per 
pieces  retain  a  smaller  volume  of  the  mixture  newly  formed  in  their  pores,  than  the 
one  piece  absorbed  of  water  alone,  and  the  other  of  saline  solution  alone.  The 
power  of  retaining  water  is  diminished  by  the  addition  of  salt  to  the  bladder 
saturated  with  water ;  liquid  is  expelled ;  but  by  the  addition  of  this  water  to  the 
bladder  moistened  with  saline  solution,  the  absorbent  power  of  this  piece  of  blad- 
der is  increased,  not  in  the  same  ratio  according  to  which  the  proportion  of  salt  is 
diminished,  but  in  a  less  ratio. 

The  experiments  above  described  show  that  the  attraction  of  the  porous  sub- 
stances for  the  water  which  they  have  absorbed  does  not  prevent  the  mixture  of  this 
water  with  other  liquids. 

The  permeability  of  animal  tissues  to  liquids  of  every  kind,  and  the  miscibility 
of  the  absorbed  liquids  with  others  which  are  brought  in  contact  with  the  tissues, 
may  be  demonstrated  by  the  simplest  experiments.* 

If  we  moisten  one  side  of  a  thin  membrane  with  ferrocyanide,  of  potassium,  and 
the  opposite  side  with  chloride  of  iron  in  solution,  we  perceive  in  the  substance  of 
the  membrane  a  spot  of  Prussian  blue  immediately  deposited.  (JoH.  MTLLER.) 

All  fluids  which,  when  brought  together,  suffer  a  change  in  their  nature  cr  in 
their  properties,  exhibit,  when  only  separated  by  an  animal  membrane,  exactly 
analogous  results  ;  they  mix  in  the  pores  of  the  membrane,  and  the  decomposition 
commences  in  its  substance. 

If  we  tie  up  one  end  of  a  cylindrical  glass  tube  with  bladder,  and  fill  it  to  the 
height  of  3  or  4  inches  with  water  or  strong  brine,  neither  the  water  nor  the  brine 
flows  out  through  the  pores  of  the  bladder/under  this  slight  pressure. 

But  if  we  leave  the  tube  containing  brine  exposed  to  evaporation  in  the  air,  the 
side  of  the  bladder  exposed  to  the  air  is  soon  covered  with  crystals  of  salt,  which 
gradually  increase,  so  as  to  form  a  thick  crust.t  It  is  obvious  that  the  pores  of  the 
bladder  become  fluid  with  brine ;  that,  on  the  side  exposed  to  the  air,  the  water 
evaporates ;  its  place  is  supplied  by  fresh  brine,  and  the  dissolved  salt  is  deposited 
at  the  external  minute  openings  of  the  pores,  in  the  form  of  crystals.  If  the  tube 
be  filled  originally  with  dilute  saline  solution,  the  crust  of  salt  is  not  formed  on  the 
outer  surface  of  the  bladder  until  the  solution  in  the  tube  has  reached,  by  evapora- 
tion, the  maximum  of  saturation.  Before  this  takes  place,  we  can  perceive  in  the  tube, 
if  we  set  the  liquid  in  motion,  two  strata,  a  heavier  and  a  lighter,  the  latter  swim- 
ming on  the  former.  When  these  strata  can  no  longer  be  observed,  the  liquid  is 
in  every  part  saturated  with  salt;  and  now,  by  further  evaporation,  crystals  are 
deposited  on  the  outer  surface  of  the  bladder.  This  last  circumstance  proves  that 
the  amount  of  salt  in  the  liquid  is  uniformly  distributed  from  below  upwards,  from 
the  specifically  heavier  to  the  specifically  lighter  part. 

If  we  immerse  the  tube  closed  with  bladder,  and  filled  with  saline  solution,  in 
pure  water,  the  latter  acquires  the  property  of  precipitating  nitrate  of  s'lver,  even 

*  Animal  tissues  are  permeable  to  liquids  of  every  kind,  which  act  on  each  othe:  in  the  sub- 
•taace  of  the  tissues, 
t  Deposition  of  salt  on  the  outside  of  bladder  from  brine  on  the  inside. 


MIXTURE  OF  THE  LIQUIDS.  15 

when  the  contact  has  lasted  only  the  fraction  of  a  second.*  The  brine  filling  th-; 
open  pores  of  the  membrane  mixes  with  the  pure  water,  and  the  latter  acquires  a 
certain  quantity  of  salt. 

In  like  manner,  the  pure  water  acquires  a  saline  impregnation,  when  it  is  placed 
in  the  tube  instead  of  brine,  and  the  outer  surface  of  the  bladder  is  placed  in  con- 
tact with  solution  of  salt. 

When  the  tube,  closed  with  bladder,  and  filled  with  brine,  is  left  for  a  long  time 
with  the  closed  end  immersed  in  pure  water,  the  amount  of  salt  in  the  latter 
increases,  while  that  of  the  brine  diminishes,  till  at  last  the  two  liquids,  separated 
by  the  bladder,  contain  the  same  relative  proportions  of  salt  and  water. 

If  the  liquid  in  the  tube  contain,  dissolved,  other  substances  which  give  to  it 
properties  different  from  those  of  pure  water,  and  if  these  solutions  be  miscible  with 
water,  the  mixture  of  them  with  the  water  takes  place  exactly  as  in  the  case  of 
brine.t  This  is  true  of  saline  solutions  of  every  kind  ;  of  bile,  milk,  urine,  serum 
of  blood,  syrup,  solution  of  gum,  &c.,  on  the  one  side,  and  pure  water  on  the  other. 
The  concentrated  liquid  loses,  the  water  or  diluted  liquid  gains,  in  regard  to  saline 
impregnation. 

If  we  fill  the  tube  with  water,  and  place  it  in  a  vessel  with  alcohol,  the  water 
becomes  charged  with  alcohol,  while  the  alcohol  becomes  diluted  with  water. 

There  is  observed,  in  these  circumstances,  that  is,  when  two  dissimilar  liquids, 
separated  by  a  membrane,  mix  together,  a  phenomenon  of  a  peculiar  kind;  namely, 
in  most  cases  a  change  of  volume  in  both  liquids,  while  the  mixture  goes  on.J 
The  one  liquid  increases  in  bulk,  and  rises ;  the  other  diminishes  in  the  same 
degree,  and  consequently  sinks  below  its  original  level. 

This  phenomenon  of  mixture  through  a  membrane,  accompanied  with  change 
of  volume,  has  been  distinguished  by  DUTROCHET,  under  the  name  of  ENDOSMOSIS 
and  EXOSMOSIS  ;  endosmose  is  the  name  given  when  the  volume  increases — exos- 
mose,  when  it  diminishes.§  Very  generally,  however,  we  attach  to  these  terms 
the  idea  of  the  unknown  cause  or  group  of  causes  which,  in  the  given  case*  produce 
the  change  of  volume  ;  in  the  same  sense  as  that  in  which  the  term  capillary  action 
includes  the  causes  which  determine  the  ascent  of  liquids  in  narrow  tubes. 

In  all  cases^  the  increase  in  volume  of  the  one  liquid  is  exactly  equal  to  the 
decrease  in  volume  of  the  other,  after  making  allowance  for  the  contraction  which 
the  liquids  undergo  by  simple  mixture  (as  in  the  case  of  alcohol  and  water,  oil  of 
vitriol  and  water,  &c.,)  as  well  as  by  evaporation.  The  unequal  concentration,  or 
the  unequal  density  of  the  two  liquids,  has  a  decided  influence  on  the  rapidity  with 
which  the  change  of  volume  takes  place  ;  but  this  cannot  be  viewed  as  the  cause 
of  that  phenomenon.  In  most  cases  the  denser  liquid  increases  in  volume,  in  others 
the  reverse  occurs. 

When,  for  example,  the  tube  contains  brine,  and'  the  outer  vessel  pure  water, 
the  brine,  that  is  the  denser  liquid,  increases  in  volume  ;[|  but  when  the  tube  con- 
tains water,  and  the  outer  vessel  alcohol,  the  water,  that  is,  the  denser  liquid, 
diminishes  in  volume. 

With  regard  to  the  mixture  of  the  liquids,  the  bladder  takes  a  distinct  share  in 
the  process,  inasmuch  as  it  has  pores,  through  which  the  two  liquids  are  brought 
in  contact. 

With  reference  to  the  porosity  of  the  bladder,  the  rapidity  of  the  mixture  of 
the  two  liquids  is  directly  proportional  to  the  number  of  particles,  which,  in  a 
given  time,  come  into  contact ;  it  depends  also  on  the  surface  (the  size  of  the  mem- 
brane,) and  on  the  specific  gravity  of  the  liquids. 

The  influence  of  extent  of  surface  on  the  time  required  for  mixture  requires  no- 
particular  elucidation ;  that  of  the  unequal  specific  gravity  is  rendered  evident  by 
the  following  experiments.^ 

*  Saline  solutions  pass  very  rapidly  through  bladder. 
fThe  same  is  true  of  bile,  milk,  urine,  serum,  &c. 

t  Change  of  volume  when  two  dissimilar  liquids  mix  through  a  bladder. 
$  Endosmosis  and  Exosmosis. 

J  The  change  of  volume  does  not  depend  alone  on  the  relative  density  of  the  liquids. 
f  Influence  of  the  unequal  density  of  the  two  liquids,  when  the  lighter  liquid  is  above  the 
membrane!. 


16 


MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 


Fig.  2.  If  the  bent  tube  a  b  (Fig.  2,)  one  end  of  which  is  tied  over  with 

bladder,  and  the  other  open,  be  filled  with  brine  colored  blue^1)  and 
if  pure  water  be  placed  in  the  tube  c,  there  is  soon  perceived  under 
the  bladder  a  colorless  or  nearly  colorless  stratum  of  liquid,  which 
continues  for  hours  to  float  in  the  same  place.  If  the  bent  tube  a  b 
be  filled  with  colorless  brine,  while  c  is  filled  with  pure  water  colored 
blue,  there  is  found,  after  a  time,  above  the  bladder,  a  colorless  or 
nearly  colorless  stratum  of  liquid. 

It  appears  from  this,  that  an  exchange  of  both  liquids  goes  on 
through  the  substance  of  the  bladder ;  in  the  first  experiment  color- 
less water  passes  from  the  tube  c  to  the  colored  brine  in  the  tube 
a  b  ;  in  the  second,  colorless  brine  passes  from  the  tube  a  b  to  the 
colored  water  in  the  tube  c. 

It  is  obvious  that  the  brine  in  the  tube  a  #,  which  is  in  contact 
with  the  bladder,  becomes  diluted  by  the  addition  of  water  from  the 
tube  c  ;  but  this  diluted  brine  is  specifically  lighter  than  the  original  brine  which 
is  below  it,  and  remains  therefore  floating  at  its  surface. 

On  the  other  hand,  the  water  in  the  tube  c,  when  mixed  with  brine  from  the 
tube  a  b,  becomes  heavier  than  the  pure  water,  and  rests,  therefore,  on  the  upper 
surface  of  the  bladder,  or  that  which  is  turned  towards  the  water. 

Hence  it  follows,  that  from  the  moment  when  these  two  strata  have  been  formed 
above  and  below  the  bladder,  neither  concentrated  brine  nor  pure  water  comes  any 
longer  in  contact  with  the  bladder. 

From  the  bladder  downwards,  in  the  tube  a  b  are  strata  of  liquid,  containing 
successively  more  salt ;  from  the  bladder  upwards  in  the  tube  c  are  strata  containing 
successively  more  water. 

In  the  beginning  of  this  experiment  we  observe,,  that  the  volume  of  the  water 
and  of  the  brine  changes  in  both  tubes  ;  the  liquid  in  the  limb  b  rises  from  1  to  2 
lines  ;  but  as  soon  as  the  strata  above  mentioned  have  been  distinctly  formed  above 
and  below  the  bladder,  hardly  any  further  rise  is  perceptible,  although  the  mixture 
of  the  liquid  proceeds,  and  the  water  in  c  becomes  constantly  more  charged  with 
salt,  while  the  brine  in  a  b  loses  salt. 

If  we  reverse  the  positions  of  the  two  liquids  in  the  apparatus 
fig.  o.  Yig.  2,  or  what  is  simpler,  if  we  close  with  bladder  a  tube 

1   centimetre  (TVhs  °f  an  inch)  wide,  fill  it  with  brine,  and 
immerse  the  end  closed  with  the  bladder  in  a  wider  vessel 
filled  with  pure  water,  giving  to  the  tube  an   inclination  of 
about   45°,    we    may    observe    (most   distinctly   when   both 
liquids  contain  some  fine  particles  of  indigo  suspended)  in 
both  liquids  a  continual  motion.*     We  see  in  the  tube  (Fig. 
a  current  of  liquid  rising  from  the  bladder  in  the  direction 
the  arrow,  and  flowing  down  again  on  the  opposite  side. 
A  similar  circulation  is  observable  in  the  vessel  of  water. 

If  the  tube  a,  with  brine,  is  about  2  centimetres  (fths  of  an 
inch)  wide,  and  if  we  support  it  vertically  in  the  vessel  b  of 
water,  the  motion  proceeds  from  the  middle,  and  in  both  the 
tube  and  the  vessel  we  perceive  currents  in  opposite  directions. 
(Fig.  4.) 

These  currents  hardly  require  explanation.  To  the  brine  in 
the  tube  «,  pure  water  passes  through  the  bladder ;  there  is  formed 
above  the  bladder  a  mixture  containing  less  salt,  and  therefore 
specifically  lighter  than  the  brine  ;  this  mixture  rises,  and  the 
denser  brine  descends  to  occupy  its  place. 

On  the  other  hand,  the  pure  water  receives  through  the  bladder 
salt,  and  becomes  thereby  specifically  heavier;  while  it  sinks  to 
the  bottom  of  the  vessel,  its  place  is  supplied  by  water  containing 


( ')  For  this  purpose  it  is  best  to  take  a  solution  of  indigo  in  sulphuric  acid,  diluted, 
*  When  the  heavier  liquid  is  above  the  membrane. 


MIXTURE  OF  TWO  LIQUIDS  THROUGH  A  MEMBRANE. 


17 


less  or  no  salt,  and  therefore  specifically  lighter,  which  again  comes  in  contact  with 
the  bladder.  As  long  as  the  motions  just  described  are  perceptible,  we  observe  a 
constant  increase  in  the  volume  of  the  brine  in  the  tube  a  (Fig.  4,)  or  a  diminution 
in  the  volume  of  the  pure  water  in  the  vessel  6.  When  the  motions  cease,  the 
rise  of  liquid  in  the  tube  is  arrested,  and  when  this  takes  place,  the  two  liquids 
are  found  to  possess  almost  exactly  the  same  specific  gravity. 

When  the  two  strata  of  liquid  on  either  side  of  the  bladder  are  little  different  in 
composition  (as  soon  comes  to  pass  in  the  experiment  (Fig.  2)  where  the  saline 
contents  of  the  liquid  which  fills  the  pores  of  the  bladder  can  hardly  vary  from 
that  of  the  next  stratum,)  the  mixture  of  the  liquids  takes  place,  but  without  further 
change  of  volume.  But  when  an  exchange  of  the  mixtures  on  the  opposite  sides 
of  the  bladder  can  occur  in  consequence  of  their  different  specific  gravity,  and 
when  a  continued  difference  between  the  strata  on  opposite  sides  of  the  bladder  is 
thus  determined,  then,  so  long  as  (in  the  case  of  brine  and  water,  for  example)  one 
side  of  the  bladder  is  in  contact  with  a  concentrated,  the  other  with  a  more  diluted 
solution,  the  change  of  volume  in  the  two  liquids  continues. 

As  appears  from  these  experiments,  the  change  of  volume  depends  on  a  difference 
in  the  character  of  the  two  liquids  which  are  connected  through  the  bladder ;  and 
the  time  during  which  change  of  volume  occurs  is  in  direct  proportion  to  the  time 
during  which  this  difference  in  character  subsists.  The  greater  the  difference  in 
character  and  composition  between  the  liquids,  and  the  more  rapidly  this  difference 
is  renewed  by  the  exchange  between  the  strata  in  contact  with  the  opposite  sides 
of  the  bladder,  the  more  rapidly  does  the  one  liquid  increase,  and  the  other 
diminish  in  volume. 

The  following  apparatus  is  very  conv-enient  for  measuring  the 
change  in  volume,  caused  by  the  mixture  of  two  liquids  separated  by 
a  membrane.* 

The  tubes  a  and  6,  (Fig.  5)  are  of  equal  width,  and  are  best  takea 
from  the  same  tube ;  a  is  closed  with  bladder,  and  filled  up  to  a  cer- 
tain point  with  the  liquid  whose  increase  in  volume  is  to  be 
determined.  It  is  then  fitted  by  means  of  a  good  cork  into  the  wider 
tube  c,  which  contains  distilled  water,  care  being  taken  to  exclude  all 
air  bubbles.  At  d  lies  a  small  lead  drop,  which  acts  as  a  valve  in 
shutting  the  opening  of  the  capillary  tube  connecting  c  with  b. 
Pure  water  is  now  poured  into  6,  and  in  order  to  keep  in  equili- 
brium the  lead  drop  at  c?,  rather  more  water  is  added  than  exactly 
suffices  to  bring  the  liquids  to  the  same  level  in  both  tubes. 

The  liquid  in  a  increases  in  volume,  and  the  height  to  which  it 
rises  may  be  read  off  by  means  of  any  division  into  equal  parts 
by  measure  ;  the  level  of  the  liquid  in  b  sinks  in  an  equal  ratio.  If 
we  keep  the  liquid  in  6,  by  the  addition  of  fresh  water,  at  the 
original  level,  and  if  we  ascertain  the  weight  of  the  added  water, 
by  pouring  it  out  of  a  dropping  bottle,  and  determining  the  loss  of 
weight  in  the  dropping  bottle,  we  learn,  at  the  same  time,  the 
•weight  and  the  volume  of  the  water  which  has  risen  from  c  into  a. 


Fig.  5. 


This  apparatus  admits,  of  course,  of  a  number  of  variations  and  improvements. 
I  have  employed  it  to  determine  the  relation  between  brine  and  water,  under  the 
circumstances  just  described.  It  appeared,  among  other  things,  that  when  the 
tube  a  is  filled  with  saturated  solution  of  sea  salt,  the  volume  of  the  liquid  increased 
by  nearly  one  half;  that  is,  200  volumes  of  such  a  solution  increased  to  300. 
These  determinations  are,  however,  not  the  object  of  the  present  investigation,  and 
therefore  I  pass  them  over  entirely. 

The  following  arrangement,  (Fig.  6)  will  probably  be  found  preferable  to  the 
one  just  described,  in  many  cases.  Its  construction  depends  on  the  observation, 
that  for  the  phenomenon  itself,  and  for  the  result  of  the  experiment,  it  is  entirely  a 

and  after  adding  subacetate  of  lead  as  long  as  sulphoindigotate  and  sulphate  of  lead  are 

precipitated,  to  separate  the  precipitate  by  filtration  and  dry  up  the  filtered  liquid  in  the 

water  bath.   A  mere  trace  of  the  blue  residue  suffices  to  color  blue  large  masses  of  liquid* 

*  The  change  in  volume  may  be  measured. 

3 


18 


MOTION  OF   THE  JUICES  OF  THE  ANIMAL  BODY. 


matter  of  indifference    whether    the  tube  be   closed    with   a  single,      Fig. 
double,  or  treble  layer  of  bladder.  (*)     For  experiments  on  very  thin         a 
membranes  which  are  permeable  to  liquids  imder  a  very  low  pressure, 
the  apparatus  (Fig.  5)  is  obviously  better  adapted.     For  the  explana- 
tion of  the  phenomenon  we  have  to  distinguish — 

1.  The  mixture  of  different  liquids. 

2.  The  change  in  their  volume. 

As  to  the  mixture  of  two  liquids  of  dissimilar  nature  and  characters, 
this  always  depends  on  a  chemical  attraction.*  In  a  mixture  of 
alcohol  and  water,  or  of  brine  and  water,  there  is  in  every  part  the 
same  proportion  of  particles  of  alcohol  and  water,  or  of  salt  and 
water.  If  in  the  former,  the  lighter  particles  of  alcohol  lying  at  the 
bottom  of  the  vessel  were  not  retained,  in  the  place  and  arrangement 
which  they  occupy,  by  the  surrounding  particles  of  water,  they  would 
undoubtedly  rise  towards  the  surface.  In  like  manner,  the  particles  of 
salt  in  the  brine  are  sustained  and  prevented  from  sinking  by  the  lighter 
particles  of  water  which  surround  them. 

Without  an  attraction,  which  all  the  particles  of  alcohol  or  of  salt 
must  have  towards  all  the  particles  of  water,  or  all  the  particles  of 
water  must  have  for  all  those  of  salt  and  alcohol,  a  uniform  mixture 
cannot  even  be  conceived.  If  but  one  particle  of  alcohol  were  less 
powerfully  attracted  than  the  surrounding  particles,  it  would  rise  to  the  surface  ; 
and  in  like  manner,  the  particles  of  salt  would,  in  consequence  of  their  greater 
specific  gravity,  gradually  occupy  the  bottom  of  the  vessel,  were  it  not  that  a  cause 
prevents  them  from  rising  or  falling ;  and  this  cause  can  be  nothing  but  an  attrac- 
tive force,  which  retains  them  in  the  place  where  they  happen  to  be. 

The  cause  which  effects  a  change  in  the  place  or  in  the  properties  of  the  ulti- 
mate particles  or  atoms  of  dissimilar  substances,  when  these  particles  are  in 
absolute  contact,  or  at  infinitely  small  distances  from  each  other,  as  well  as  the 
cause  which  manifests  itself  as  a  resistance  to  such  changes  of  place  or  properties, 
we  call  CHEMICAL  ATTRACTION  ;t  and  in  this  sense  the  mixture  of  two  dissimilar 
liquids,  the  simple  moistening  of  a  solid  body,  the  penetration  and  swelling  of  it 
by  a  liquid,  are  effects  in  which  chemical  affinity  or  attraction  has  a  decided  share  ; 
and  although  we  are  accustomed  to  limit  the  notion  of  affinity  to  such  cases  as 
exhibit  a  change  perceptible  to  our  senses,  in  the  properties  of  the  substances 
employed,  as,  for  example,  when  sulphuric  acid  and  lime,  or  sulphuric  acid  and 
mercury  combine  together,  this  limitation  arises  from  the  imperfect  apprehension 
of  the  essence  of  a  natural  force. 

Every  where,  when  two  dissimilar  bodies  come  in  contact,  chemical  affinity  is 
manifested.  It  is  a  universal  property  of  matter,  and  by  no  means  belongs  to  a 
peculiar  class  of  atoms,  or  to  a  peculiar  arrangement  of  these.  But  chemical 
combination  is  not,  in  all  cases,  the  result  of  contact. 

Combination  is  only  one  of  the  effects  of  affinity,  and  occurs  when  the  attrac- 
tion is  stronger  than  all  the  obstacles  which  are  opposed  to  its  manifestation. \ 
When  the  forces  or  causes,  which  oppose  chemical  combination,  heat,  cohesive 
attraction,  electric  attraction  or  whatever  they  may  be  called,  preponderate,  then 
chemical  combination  does  not  take  place ;  and  effects  of  another  kind  are 
manifested. 

Melted  silver  in  a  crucible,  surrounded  with  red  hot  coals,  in  a  place,  therefore, 
where  we  should  hardly  anticipate  the  presence  of  free  oxygen,  absorbs  as  much 


(!)  In  these  experiments  membranes  of  all  kinds  may  be  used.  With  the  thinner 
membranes,  such  as  the  bladder  of  the  calf  and  the  pig,  the  experiments  are  more 
rapidly  completed  than  with  the  thicker,  such  as  the  gall-bladder  and  urinary  bladder 
of  the  ox.  The  peritoneum  of  the  ox  and  calf  is  preferable  to  all  others.  The  tube  c 
is  tied  with  bladder  under  water. 

*  Causes  of  the  mixture  of  dissimilar  liquids. 

t  Chemical  affinity  is  the  chief  cause  of  mixture. 

;  Affinity  is  everywhere  active  between  bodies  in  contact 


CHEMICAL  AFFINITY  IS  UNIVERSALLY  DIFFUSED.  19 

as  ten  or  twelve  times  its  volume  of  that  gas.  Metallic  platinum  exhibits  the  same 
property  in  a  far  higher  degree  ;  for  from  the  atmospheric  air,  *  gaseous  mixture 
in  which  oxygen  forms  only  the  fifth  part,  that  metal  (in  the  form  of  a  black 
powder)  condenses  on  its  surface,  at  the  ordinary  temperature,  an  enormous  quantity 
of  oxygen  gas  (without  any  nitrogen,)  and  acquires  thereby  properties,  which  it 
does  not  otherwise  possess.^)  And  when  oxide  of  chromium,  fragments  of  porce- 
lain, or  asbestus,  at  high  temperatures,  effect  the  combination  of  two  gases, 
oxygen  and  hydrogen,  or  oxygen  and  sulphurous  acid,  which  gases  do  not  combine 
at  the  same  temperature,  unless  when  in  cqntact  with  these  solid  bodies,  it  is  to  the 
chemical  attraction  or  affinity  of  these  solid  bodies  that  we  must  ascribe  this 
effect. 

The  solution  of  a  salt  in  water  is  an  effect  of  affinity,  and  yet  no  one  property, 
either  of  the  salt  or  of  the  solvent,  is  thereby  altered,  except  only  the  cohesion  of 
the  saline  particles. 

Sea  salt,  the  crystals  of  which  are  usually  anhydrous,  takes  up,  at  very  low 
temperatures,  38  per  cent,  of  water  of  crystallization  ;*  not  because  any  new 
cause  acts  which  increases  its  affinity  for  the  particles  of  water  (for  cold  is  no 
cause,  but  the  absence  of  a  cause,)  but  because  the  higher  temperature  acted  as  an 
obstacle,  opposing  their  chemical  combination.  The  force  of  affinity  is  all  the 
time  present  and  undiminished. 

When  we  add  alcohol  to  the  solution  of  a  salt  in  water,  we  observe,  that  now 
the  salt  separates  from  the  liquid  in  the  form  of  crystals,  doubtless  only  because, 
by  the  addition  of  another  chemical  force,  the  amount  of  attraction  between  the 
particles  of  the  salt  and  those  of  the  water  has  been  altered. 

The  aqueous  particles,  which  were  combined  with  the  saline  particles,  manifest 
an  attraction  for  the  particles  of  alcohol ;  and  as  the  latter  have  no  affinity,  or  only 
a  very  feeble  affinity,  for  those  of  the  salt,  the  attraction  of  the  saline  particles  for 
each  other  is  strengthened.  This  attraction  was  present  in  equal  force  before  the 
addition  of  the  alcohol,  but  the  resistance  which  opposed  their  union  (the  chemical 
attraction  for  them  of  the  aqueous  particles)  was  more  powerful.!  The  alcohol  was 
not  the  cause  of  the  separation.  The  cause  of  the  separation  of  the  salt  from  the 
liquid,  its  crystallization,  is  at  all  times  the  force  of  cohesion ;  and  by  the  alcohol 
the  cause  which  opposed  its  manifestation  was  removed. 

The  affinity  of  potash  for  sulphuric  acid  is  known,  and  sulphate  of  potash 
readily  dissolves  in  water.  If  we  add,  to  a  saturated  solution  of  that  salt,  an 
equal  volume  of  aqua  potassae  of  sp.  g.  1.4,  there  is  immediately  formed  a  crystal- 
line precipitate  of  sulphate  of  potash,  and  the  sulphuric  acid  is  separated  in  this 
form  from  the  water. 

In  these  cases  the  chemical  effect  (the  separation)  depends  on  the  presence  of  a 
certain  quantity  of  the  liquid  which  is  added  (such  as  aqua  potassse,  alcohol,  &c.,) 
but  in  many  other  cases  there  is  required  only  a  slight  alteration  in  the  quality  of 
the  solvent  to  effect  separations  of  this  kind. 

When  hydrochloric  acid  is  added  to  a  solution  of  ferrocyanide  of  potassium, 
ferrocyanic  acid  is  set  free,  and  remains  dissolved  in  the  liquid.  If  now  the  vapor 
of  boiling  ether  be  passed  rhrough  the  mixture,  there  occurs,  after  a  few  moments, 
a  complete  separation.  The  whole  of  the  ferrocyanic  acid  is  deposited  from  the 
liquid  in  the  form  of  white  or  bluish-white  crystalline  scales,  which  generally 
appear  in  such  quantity  as  to  render  the  whole  mass  semisolid.  In  proportion  as 
the  vapor  of  ether  is  dissolved  by  the  water,  the  latter  fluid  loses  entirely  its  solvent 
power  (its  affinity)  for  the  ferrocyanic  acid.  The  coagulation  of  albumen  by- 
ether  depends  on  a  similar  cause. 

The  capacity  of  solids  to  become   moistened   by   liquids,   and,  in    short,  all 

(!)  According  to  Dcebereiner,  platinum  black  condenses  252  times  its  volume  of 
Dxygen.  Its  effect  in  oxidizing  alcohol,  pyroxilic  spirit,  &c.,  is  familiar  to  every 
chemist. — W.  G. 

*  Crystallization  of  sea  salt. 

i  Precipitation  of  salt  from  its  solution  by  alcohol ;  of  sulphate  of  potash  by  caustic  potash;  of 
ferocyanic  acid  by  ether  ;  of  suspended  mud  by  alum. 


20  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

phenomena  connected  with  chemical  affinity,  are  affected,  altered,  increased,  or 
destroyed  by  causes  quite  analogous. 

After  heavy  rains,  the  water  of  many  rivers  becomes  turbid  and  opaque  from 
the  presence  of  a  fine  clay.  These  suspended  particles  of  clay  are  so  fine  as  to 
pass  through  the  finest  filters ;  and  their  adhesion  to  the  water  is  so  great,  that 
such  water  does  not  clear  after  standing  for  weeks.  The  water  of  the  Yellow 
River,  in  China,  possesses,  during  the  greater  part  of  the  year,  this  character  ;  and 
from  the  French  missionaries,  we  know  that  alum  is  universally  employed  in  Pekin 
to  clear  it.  In  fact,  if  a  crystal  of  alum  be  held  in  such  a  water  only  for  a  few 
seconds,  we  observe  the  sediment  separating  in  large  thick  flocculent  masses,  the 
"water  becomes  transparent,  and  hardly  a  trace  of  dissolved  alum  is  to  be  detected 
by  the  most  delicate  re-agents.  Chemistry  is  acquainted  with  a  number  of  similar 
means  for  causing  the  separation  from  liquids  of  suspended  precipitates.. 

In  these  cases  we  see,  that  by  an  alteration  of  the  quality  of  the  water,  produced 
by  what  we  call  mere  mixture  with  a  foreign  body,  its  power  of  combining  with 
Others  is  destroyed  or  weakened. 

It  is  well  known  that  the  force  with  which,  in  a  solution,  the  particles  of  the 
liquid  and  those  of  the  dissolved  body  attract  each  other,  is  very  unequal  in  different 
cases  ;*  and  in  this  point  of  view  the  action  of  many  solid  bodies  on  saline  solu- 
tions is  very  remarkable  ;  inasmuch  as  it  is  thereby  demonstrated,  that  the  mole- 
cular force,  which  determines  the  phenomena  of  cohesion,  and  the  moistening  of 
solid  bodies  by  liquids  appears  to  be  identical  with  chemical  affinity,  since  chemical 
compounds  can  be  decomposed  by  means  of  it.  Professor  GRAHAM  has  shown 
fliat  common  charcoal,  deprived  by  acids  of  all  soluble  ingredients,  completely 
removes  the  metallic  salts  or  oxides  from  solutions  of  salts  of  lead,  tartar  emetic, 
ammoniated  oxide  of  copper,  chloride  of  silver  in  ammonia,  and  oxide  of  zinc  in 
ammonia ;  while  other  solutions,  such  as  that  of  sea  salt,  suffer  no  such  change. 
A  bleaching  solution  of  hypochlorite  of  soda  loses  entirely  its  bleaching  properties 
by  agitation  with  charcoal ;  and  iodine  can  be  removed  by  the  same  means  from 
its  solution  in  iodide  of  potassium.  Every  one  is  familiar  with  the  action  of  finely- 
divided  platinum,  with  that  of  silver  on  the  deutoxide  of  hydrogen ;  as  well  as 
with  that  of  charcoal  on  dissolved  organic  matters,  coloring  matters,  &c.  ;  and 
freshly-precipitated  sulphuret  of  lead,  sulphuret  of  copper,  and  hydrate  of  alumina, 
resemble  the  latter  in  their  action.  Many  organic  substances,  such  as  woody  fibre 
and  others,  act  on  dissolved  matters,  such  as  salts  of  alumina  or  of  oxide  of  tin, 
just  as  charcoal  does;  and  we  know  that  the  application  of  mordants  in  dyeing, 
and  dyeing  itself  depend  on  this  very  property.  The  adhesion  of  the  solid  coloring 
matter  to  the  cloth  which  is  died  with  it  is  the  result  of  a  chemical  affinity  so  feeble, 
that  we  hardly  venture  to  give  the  molecular  force  that  name  in  this  case.  From 
a  piece  of  woollen  cloth  dyed  with  indigo,  the  indigo  is  completely  separated,  by 
mere  beating,  continued  for  some  time,  with  a  wooden  hammer,  so  that  the  wool 
is  at  last  left  white. 

The  surface  of  the  solid  body  exerts,  as  these  facts  prove,  a  very  unequal  attrac- 
tion on  the  molecules,  which  come  in  contact  with  it. 

Researches  on  capillary  attraction  have  shown  that,  with  one  and  the  same 
liquid,  water,  for  example,  the  substance  of  the  solid  body  has  no  influence  on 
Ihe  height  to  which  the  liquid  rises  on  it.  On  slices  of  box-wood,  clay-slate,  or 
glass,  the  rise  of  the  liquid  above  the  surface  of  the  water  is  the  same  exactly  as 
in  the  case  of  a  plate  of  brass.  (HAGEN.)  In  the  case  of  other  liquids,  the  par- 
ticles of  which  are  entirely  homogeneous,  the  same  law  may  be  assumed  in  theory  ; 
but  with  such  liquids  as  contain  foreign  bodies  in  solution,  a  change  in  the  capillary 
attraction  must  be  produced  by  the  presence  of  these  bodies,  because  by  them  the 
cohesion  of  the  liquid  is  altered ;  and,  perhaps,  still  more  because  the  liquid 
ceases  to  be  homogeneous,  when  the  attracting  wall  has  a  stronger  affinity  for  the 
particles  of  the  dissolved  body  than  for  those  of  the  solvent. 

From  what  has  been  stated,  it  appears,  that  the  mixture  of  two  liquids  is  the 
result-  of  a  chemical  attraction ;  for  how  otherwise  could  chemical  compounds, 

*  Action  of  solids  on  dissolved  matters. 


LAWS  OF  THE  MIXTURE  OF  DIFFERENT  LIQUIDS.  21 

such  as  the  solution  of  a  salt  in  water,  be  decomposed,  or  a  chemical  attraction  be 
overcome,  by  its  means  ? 

Two  liquids  of  different  chemical  properties,  which  are  miscible  together,  and 
which,  therefore,  have  a  chemical  attraction  for  each  other,  mix  readily  at  all  points 
where  they  come  in  contact.*  By  motion,  shaking,  &c.,  the  number  of  points  of 
contact  within  a  given  time  is  increased,  and  the  formation  of  a  uniform  mixture 
is  thus  accelerated. 

If  these  liquids  be  of  equal,  or  still  better,  of  unequal,  specific  gravity,  they 
may  be,  with  the  aid  of  some  precaution,  stratified  one  above  the  other.  This  is, 
in  point  of  time,  the  most  unfavorable  case  for  the  mixture,  since  proportionally 
small  surfaces  come  in  contact.  But  wherever  they  do  come  in  contact,  it  is, 
after  a  very  short  time,  impossible  to  detect  any  limit  between  them. 

In  a  cylindrical  vessel  containing  solution  of  salt,  the  saline  particles  at  the 
surface  are  attracted  and  sustained  by  aqueous  particles,  which  exist  at  the  sides  of 
the  saline  particles  and  from  the  surface  downwards.  From  the  surface  upwards, 
the  attracting  aqueous  particles  are  absent. 

Now  it  is  evident  that  when  the  surface  is  brought  in  contact  with  pure  water, 
a  new  attraction  is  added  to  those  previously  existing,  which  acts  in  an  opposite 
direction,  namely,  the  attraction  of  the  aqueous  particles  floating  on  the  surface  for 
the  saline  particles,  and  vice  versa  (the  attraction  of  the  saline  particles  to  the 
aqueous  particles  in  contact  with  them.) 

At  the  place  where  pure  water  and  brine  are  in  contact,  there  is  thus  formed  a 
uniform  mixture  of  the  two,  which  upwards  is  in  contact  with  pure  water,  down- 
wards with  brine. 

Among  these  three  strata,  of  which  the  upper  contains  no  salt,  the  lower  less 
water,  a  new  division  takes  place ;  the  more  strongly  saline  stratum  loses  salt,  the 
pure  water  becomes  saline,  and  in  this  way  salt  and  water  are  at  last  uniformly 
distributed  throughout  the  liquid. 

If  we  fill  one  limb  of  the  tube  (Fig.  7,)  as  far  as  a,  with  brine 
colored  blue,  and  the  other  limb  with  water,  we  find,  in  the  course 
of  a  few  days,  the  water  colored  blue,  and  the  proportion  of  salt  in 
both  limbs  equal.t  It  has  been  mentioned  at  p.  15,  that,  in  a  tube 
closed  with  bladder,  filled  with  diluted  solution  of  salt,  and  exposed 
to  evaporation,  the  salt  is  not  deposited  in  crystals  on  the  outer  sur- 
face of  the  bladder  till  the  whole  liquid  in  the  tube  has  reached,  in 
consequence  of  evaporation  the  maximum  of  saturation.  The 
water  evaporates  from  the  exterior  of  the  bladder,  but  no  salt  is  de- 
posited, as  long  as  a  liquid  exists  within  which  can  still  dissolve 
salt ;  and  in  this  way  the  heavier  saline  particles  are  distributed  to- 
wards the  interior,  and  upwards  through  the  whole  liquid,  or,  what 
amounts  to  the  same,  the  lighter  aqueous  particles,  which  can  still 
dissolve  salt,  are  distributed  downwards  towards  the  external  surface 
of  the  bladder. 

This  distribution  of  salt  through  water  takes  place  in  the  same  manner  as  the 
conversion  of  bar  iron  into  steel.J  Rods  of  malleable  iron,  as  is  well  known,  are 
kept  ignited  between  strata  of  charcoal,  whereby  the  surface  of  the  iron  in  contact 
with  the  charcoal  takes  up  carbon,  and  becomes  a  carburet  of  iron.  The  stratum 
of  iron  lying  next  under  this  surface,  which  has  the  same  attraction  for  carbon, 
acquires  carbon  from  the  superficial  stratum  immediately  in  contact  with  it,  and 
in  its  turn  gives  carbon  to  the  stratum  below  itself.  This  process,  if  continued 
long  enough,  has  no  limit  till  all  the  strata  of  particles  have  acquired  an  equal 
proportion  of  carbon,  that  is,  till  they  are  all  saturated  with  it.  A  piece  of  red-hot 
malleable  iron,  if  kept  a  few  moments  in  contact  with  pig  iron  (a  carburet  of  iron) 
is  found  to  be  already  converted  into  steel  at  the  points  of  contact.  The  mixture 
of  liquids  depends  on  the  same  principle  ;  and  we  may  suppose  that  tli^L  distri- 

*  Laws  of  mixture  9f  two  liquids. 

t  Experiment  showing  the  uniform  mixture  of  two  liquids. 

JThe  distribution  of  salt  through  water,  resembles  the  conversion  of  iron  into  steel  by 
cementation. 


22  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

bution  is  mutual,  because  their  particles  may  move  in  all  directions,  and  that 
consequently  saline  particles  move  towards  aqueous  particles,  as  well  as  aqueous 
towards  saline  particles,  in  virtue  of  their  mutual  attraction. 

From  a  solution  of  sulphate  of  copper  in  ammonia,  placed  in  a  tall  glass  cylinder, 
there  is  gradually  separated,  if  we  pour  a  stratum  of  alcohol  on  the  surface,  and  if  we 
prevent -the  formation  of  a  coherent  crust  which  impedes  the  contact  of  the  liquids, 
the  whole  of  the  ammoniated  sulphate  of  copper,  while  the  deep  blue  solution 
becomes  colorless,  because  by  the  distribution  of  the  alcohol  through  the  solution 
a  mixture  is  formed,  in  which  the  salt  is  insoluble. 

Thevrapidity  of  mixture  of  two  liquids  depends  on  the  degree  of  their  chemical 
affinity  ;*  and  the  unequal  mobility  of  the  particles  of  one  or  the  other  liquid  has 
a  favorable  or  unfavorable  influence  on  the  result. 

When  the  one  liquid  is  heavier  than  the  other,  and  of  tough,  viscid  consistence, 
a  much  longer  time  elapses  before  the  ingredients  of  the  tougher  or  heavier  liquid 
reach  the  surface  from  the  bottom  of  the  vessel;  and  in  this  case  the  greater 
density  and  the  less  mobility  of  the  particles  are  obstacles  to  the  mixture. 

On  the  other  hand,  if  the  heavier  or  more  viscid  liquid  be  placed  above  the 
lighter,  the  mixture  takes  place  rapidly ;  at  the  points  where  both  liquids  are  in 
contact  is  produced  a  mixture,  which,  being  heavier,  descends,  whereby  the  heavier 
liquid  above  is  continually  brought  in  contact  with  new  surfaces  of  liquid. 

The  very  same  phenomenon  is  observed  in  solution.!  A  fragment  of  sugar, 
when  covered  with  water  at  the  bottom  of  a  narrow  cylinder,  dissolves  very  slowly, 
while,  if  suspended  just  below  the  surface,  it  rapidly  disappears.  In  the  former 
case  there  is  produced  round  the  sugar  a  thick  syrupy  viscid  solution,  which 
protects  the  undissolved  part  of  the  sugar  for  a  long  time  from  contact  with  the 
water ;  in  the  latter  there  is  formed  at  the  surface  a  solution,  which  descends  in 
striae,  and  gradually  disappears,  while  by  the  change  of  place  thus  induced,  new 
portions  of  water  are  constantly  brought  in  contact  with  the  undissolved  sugar, 
and  are  thus  enabled  to  exert  their  solvent  powers. 

If  skin  and  membranes  consist  of  a  cohering  system  of  very  narrow  tubes,  it  is 
obvious,  that  when  two  dissimilar,  but  miscible  liquids  are  separated  by  such  a 
tigs  ae,  the  pores  of  the  tissue  will  fill  with  each  of  the  two  liquids.  In  all  situations, 
\uiere  the  liquids  came  in  contact  in  the  substance  of  the  membrane,  a  mixture 
takes  place,  and  this  mixture  is  extended  equally  towards  both  sides. 

If  there  be  brine  on  one  side  of  the  bladder,  and  water  on  the  other,  there  must 
be  formed,  in  the  middle,  or  at  some  point  of  the  bladder,  a  diluted  brine,  which 
or  tne  side  in  contact  with  the  water  yields  salt  to  that  water,  while  on  the  opposite 
side  the  strong  brine  mixes  with  the  diluted  brine  in  the  bladder. 

The  substance  of  the  bladder  has  no  influence  on  this  mixture,  because  it  can 
produce  no  change  of  place  on  the  part  of  the  saline  or  aqueous  particles,  for  this 
is  the  result  of  the  chemical  affinity  acting  between  the  particles  of  salt  and  those 
of  water. 

J  Now  since  the  rapidity  of  the  mixture  of  two  liquids  stands  in  a  direct  pro- 
portion to  the  amount  of  surfaces  coming  into  contact  within  a  given  time,  and 
since  the  liquids,  separated  by  a  bladder,  can  only  come  in  contact  through  its 
pores,  while  the  number  of  points  of  contact  is  diminished  by  the  presence  of  the 
non-porous  parls  of  the  bladder,  it  follows,  that,  exclusive  of  all  other  effects,  the 
time  required  for  mixture  must  be  lengthened  by  the  interposition  of  a  bladder. 
In  the  absence  of  the  bladder,  the  mixture  would  take  place  exactly  as  when  it  is 
present,  except  in  regard  to  time. 

When  the  heavier  brine  is  under,  the  water  above  the  bladder,  the  two  liquids 
mix  more  slowly  than  without  the  bladder. 

But  since  a  bladder,  inasmuch  as  a  feeble  hydrostatical  pressure  is  not  propagated 
through  its  pores,  allows  us  to  place  a  heavier  liquid  above  a  lighter,  and  to  retain 


*  Mixture  is  influenced  by  chemical  affinity,  by  unequal  mobility,  and  by  unequal  density  in 
the  liquids. 

t  Effect  of  position  on  the  solution  of  a  solid. 
$  Rapidity  of  mixture. 


CHANGE  OF  MIXTURE  IN  LIQUIDS.  23 

it  in  that  position;  this  circumstance  has  the  effect  of  promoting  mixture,  the 
ultimate  cause  of  which  is,  not  the  bladder,  but  the  specific  gravity  of  the  liquid.* 
The  bladder  is  a  means  of  enabling  the  specific  gravity  to  influence  mixture.  The 
foregoing  remarks  appear  to  me  sufficiently  to  elucidate  the  share  taken  by  the 
bladder  in  the  mixture  of  two  dissimilar  liquids  placed  on  opposite  sides  of  "it. 

With  respect  to  the  change  of  volume  in  the  two  liquids  which  become  mixed 
through  the  bladdeis,  we  must  consider,  that  the  moistening  or  absorbent  power  of 
a  solid  body,  as  well  as  the  power  of  a  liquid  to  moisten  other  bodies,  is  the 
result  of  a  chemical  action.t  Liquids  of  different  properties,  or  of  different 
chemical  characters,  are  attracted  with  unequal  degrees  of  force  by  solid  bodies, 
and  exert  towards  them  unequal  degrees  of  attraction,  and  if  we  alter  even  in  a 
system  of  capillary  tubes,  filled  to  a  certain  height  with  a  liquid,  the  chemical 
nature  of  that  liquid,  we  change  thereby  the  height  at  which  the  liquid  stands. 
In  an  animal  tissue  saturated  with  water,  the  water  is  prevented  from  flowing  out 
by  the  mutual  attraction,  and  by  the  capillary  force,  but  if  the  attraction  of  the 
organic  parietes  for  water  be  diminished  by  the  addition  of  alcohol  or  of  salt  to  the 
water,  a  part  of  it  flows  out.  To  this  must  be  added,  that  the  water  absorbed  by 
an  animal  texture  when  it  enters  the  capillary  tubes,  exerts,  in  virtue  of  its  attrac- 
tion for  the  tubes,  a  certain  pressure,  by  which  the  vessels  are  swoln  and  enlarged. 
The  particles  of  liquid  in  these  tubes  undergo  a  counter-pressure  from  the  elastic 
parietes,  by  which  pressure,  when  the  attraction  of  the  liquid  particles  for  the 
solids  is  diminished  by  any  new  cause,  the  amount  of  expelled  fluid  is  increased. 

The  organic  parietes  of  the  tubes,  saturated  with  water,  are  affected  by  alcohol 
just  as  a  salt  is  when  dissolved  in  water.  On  the  addition  of  alcohol,  or  of 
another  liquid,  the  water  separates  from  the  salt,  or  from  the  parietes,  or  the  parietes 
separate  from  the  water. 

If  the  animal  tissue  possessed  as  great  an  attraction  for  the  newly-formed  mixture 
as  for  the  water  alone,  the  volume  of  the  liquid  would  not  change.  The  mixture 
would  take  place,  but  no  water  would  flow  out. 

A  bladder,  saturated  with  water,  when  brought  in  contact  with  alcohol,  shrinks 
together,  a  part  of  the  water  separates  from  the  animal  matter,  but  there  always 
remains  in  the  bladder  a  certain  amount  of  water,  corresponding  to  its  attraction 
for  the  bladder  and  for  the  alcohol;  just  as  the  solutions  of  many  salts  which  have 
a  strong  attraction  for  water  (such  as  a  metaphosphate  and  acid  phosphate  of  soda,) 
and  are  insoluble  in  alcohol,  are  separated  by  the  addition  of  alcohol  into  two  strata 
of  liquid,  the  heavier  of  which  is  a  more  concentrated  solution  of  the  salt  in  water, 
containing  a  little  alcohol,  while  the  other,  the  lighter,  is  an  aqueous  liquid  con- 
taining much  alcohol.  The  alcohol  and  the  salt  divide  between  them  the  water  of 
the  solution. 

When  we  add,  to  a  mixture  of  equal  parts  of  acetone  and  water,  a  certain  quan- 
tity of  dry  fragments  of  chloride  of  calcium,  the  first  fragments  which  are  added 
deliquiesce  and  dissolve  entirely  in  the  mixture.^  But  if  we  go  on  adding  the  salt, 
a  separation  soon  occurs,  two  strata  of  liquid  are  formed,  of  which  the  upper  con- 
tains acetone  and  water,  the  other  is  an  aqueous  solution  of  the  chloride  with  a 
little  acetone.  If  we  add  still  more  of  the  chloride,  water  is  abstracted  from  the 
acetone  of  the  upper  stratum,  and  when  a  proper  quantity  has  been  added,  the 
acetone  retains  no  trace  of  water. 

If  we  suppose,  that  of  the  two  originally  formed  strata  of  liquid,  one  of  them, 
namely  that  which  sinks  and  contains  chloride  of  calcium  dissolved,  is  in  contact 
with  a  current  of  dry  air,  the  water  of  this  solution  will  evaporate,  the  solution  will 
thus  become  stronger,  and  in  consequence  of  its  increased  concentration  will  be 
able  to  remove  a  new  portion  of  water  from  the  mixture  of  acetone  and  watei 
above  it  ;  and  this  will  continue  till  the  acetone  is  entirely  deprived  of  water. 

If  in  the  place  of  the  chloride  of  calcium  we  put  a  bladder,  and,  in  place  of  the 
acetone  and  water,  diluted  alcohpl,  we  have  the  finest  example  of  the  unequal 

*In  certain  circumstances,  the  interposition  of  a  membrane  accelerates  mixture. 
fChange  of  volume  in  liquids  which  mix  through  a  membrane  is  the  result  of  chemical  affinity 
modifying  capillary  attraction. 
J  Action  of  chloride  of  calcium  on  a  mixture  of  acetone  and  water. 


24  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

attraction  which  the  animal  tissue  exerts  on  the  two  ingredients  of  the  mixed 
liquid.* 

It  is  known  from  the  experiments  of  SOEMMERING,  that  spirits  of  a  certain 
strength,  inclosed  in  a  bladder,  which  is  opposed  to  the  air,  lose  by  evaporation 
only  water,  and  that  at  last  anhydrous,  or  nearly  anhydrous  (absolute)  alcohol  is 
left  in  the  bladder.  When  strong  spirits  of  wine  are  used,  the  bladder  remains  dry 
externally ;  when  weaker  spirits  are  employed,  it  becomes  moist,  and  alcohol 
evaporates  with  the  water.  In  virtue  of  the  unequal  affinity  of  the  bladder  for 
alcohol  and  for  water,  a  complete  separation  is  here  effected.  The  water  of  the 
mixture  is  absorbed  and  evaporates  from  the  outside  of  the  bladder ;  the  alcohol 
remains  in  the  bladder.  As  yet,  we  are  acquainted  with  no  substance  which  can 
replace  the  bladder  in  this  operation  ;  and  indeed,  the  affinity  of  the  gelatinous 
tissues  (membranes,  &c.)  for  water  must  exceed  that  of  all  other  animal  tissues, 
since  a  rise  of  temperature,  of  a  few  degrees  only,  suffices  to  enable  water  to 
dissolve  that  tissue  perfectly  into  a  jelly. 

MEGNUS  assumes,  "  that  the  particles  of  every  solution,  for  example,  of  a  salt  in 
water,  adhere  more  strongly  to  each  other  than  do  those  of  the  solvent,  for 
example,  of  water;  consequently,  the  solution  would  be  less  fluid,  and  pass  with 
greater  difficulty  through  very  narrow  openings,  than  water,  if  we  take  for  granted 
that  the  parietes  of  the  openings  act  alike  towards  both.  It  would  follow  from 
this,  that,  the  more  concentrated  a  solution,  the  less  easily  would  it  pass  through 
the  same  openings."! 

"  Let  us  now  try,"  pursues  MAGNUS,  "  with  the  aid  of  these  assumptions, 
(which,  as  appears  from  the  experiment  Fig.  1,  are  perfectly  accurate  and 
demonstrable  for  many  saline  solutions,  although  there  are,  according  to  the 
researches  of  POISEULLE,  a  number  of  exceptions^) )  to  explain  the  phenomena 
of  ENDOSMOSIS." 

"  Both  the  brine  and  the  water  will  penetrate  into  the  pores  of  the  bladder,  and 
brine  will  pass  *rom  the  pores  to  the  water,  as  well  as  water  to  the  brine,  in  virtue 
of  their  mutual  attraction,  till  a  complete  equilibrium  is  established.  Further, 
since  the  force  which  attracts  the  water  to  the  brine  is  exactly  the  same  as  that 
which  attracts  the  brine  to  the  water,  as  much  water  as  brine  would  pass  through 
the  bladder,  if  both  liquids  could  pass  with  equal  facility  through  the  pores. 
Since,  however,  this  is  not  the  case,  unequal  forces  are  required  to  urge  the  two 
liquids  through  the  pores ;  or  with  equal  forces,  unequal  quantities  of  the  two  pass 
through  in  equal  times.  There  is  consequently  added  more  of  that  which  passes 
most  easily,  the  water  to  the  brine,  than  of  the  latter  to  the  water,  and  the  level  of 
both  liquids  must  change,  if  no  other  force  oppose  this  change. "(3) 

According  to  this  theory,  brine  and  water  exist  in  the  pores  of  the  bladder  in  a 
state  of  motion,  and  the  chemical  affinity,  which  the  particles  of  the  brine  have 
for  the  particles  of  the  pure  water,  and  conversely,  which  the  particles  of  water 
have  for  those  of  salt,  is  considered  as  the  cause  of  this  motion.  The  unequal 
velocity,  which  makes  more  water  flow  in  a  given  time  to  the  brine  than  brine  or 
salt  to  the  pure  water,  is,  according  to  MAGNUS,  determined  by  the  unequal 
resistance  which  the  substance  of  the  bladder  opposes  to  the  passage  of  the  two 
liquids. 

Now,  however  narrow  the  tubes  may  be,  in  which  molecules  are  set  in  motion 
by  an  external  force,  it  may  always  be  assumed,  that  that  part  of  the  molecules, 
which  is  immediately  in  Contact  with  the  wall  of  the  tube,  either  is  not  in  motion, 
or  possesses  only  a  snfall  velocity,  and  the  velocity  of  efflux  must  be  a  function  of 
the  cohesion,  and  at  all  events  not  dependent  on  the  wall  of  the  tube. 

If  now  the  efflux  of  the  water  on  one  side  of  the  bladder  is  produced  by  the 
attraction  of  the  saline  particles  for  the  water,  and  the  efflux  of  the  brine  on  the 
other  side  is  produced  by  the  attraction  of  the  aqueous  particles  for  the  saline 

(*)  Ann.  de  Ch.  et  de  Phys.  3rd  series,  xxi.  pp.  84  et  seq. 
(2)  PoggendorfPs  Annales,  x.  p.  164. 

*  Effect  of  evaporation  through  a  bladder  in  concentrated  alcohol 
t  Views  of  Magnus  on  Endosrnosis. 


ATTRACTION   OF  THE    MEMBRANE  FOR  LIQUIDS.  25 

particles,  it  is  impossible  to  explain  how  water  and  brine  can  move  in  the  same 
tube  with  unequal  velocity  in  opposite  directions ;  the  two  liquids  being  supposed 
to  have  a  mutual  attraction,  that  is,  to  be  miscible.  This  attraction  must  act  with- 
in the  tube  just  as  well  without ;  and  we  might,  therefore,  suppose,  that  when  the 
two  liquids  have  become  mixed,  the  mixture  could  only  move  in  one  direction  with 
a  medium  velocity. 

Assuming  that  a  mixture  is  formed  in  the  open  orifices  of  the  pores  or  tubes,  or 
in  any  part  of  them,  it  is  difficult  to  see,  why  saline  particles  should  not  pass  from 
one  side  to  the  water,  or  aqueous  particles  to  the  saline  ones  in  the  bladder,  since 
the  mutual  attraction  must  be  regarded  as  equal  on  both  sides.  The  chemical 
affinity  of  the  two  liquids  does  not  explain  the  efflux. 

If  we  suppose,  that  in  certain  pores  only  brine,  in  others  only  pure  water 
moves,  the  phenomenon  ought  not  to  occur  when  all  the  pores  are  filled  with 
water  or  with  brine,  or  when  the  tube  is  tied  with  a  double,  treble,  or  fourfold, 
bladder.  But  the  properties  of  bladder  are  seen  in  the  finest  as  well  as  thickest 
membranes,  and  one,  two,  or  three  layers  make  no  difference  in  the  ultimate 
result.^) 

The  kind  of  influence  which  the  nature  of  the  partition,  or  its  attraction  for  the 
liquids  in  contact  with  it,  exerts  on  the  phenomenon,  is  seen  by  comparing  the  action 
of  an  animal  membrane  with  that  of  a  thin  sheet  of  caoutchouc.* 

In  a  tube,  closed  with  bladder,  which  is  filled  with  alcohol,  and  immersed  in 
pure  water,  the  volume  of  alcohol  is  increased ;  more  water  passes  to  the  alcohol 
than  alcohol  to  the  water.t 

If,  without  making  any  other  change  in  the  experiment,  the  tube  be  closed  with 
a  thin  sheet  of  caoutchouc,  the  volume  of  the  alcohol  now  diminishes  while  that  of 
the  water  increases. 

Here,  all  the  circumstances  of  the  mixture  of  the  two  liquids  have  remained  the 
same  except  the  nature  of  the  partition,  which  makes  the  difference  in  the  result. 

When  we  fill  with  brine  a  tube,  closed  with  bladder,  (Fig.  8,)  j^ff  g 

and  place  it  in  a  vessel  of  water,  so  that  the  bladder  and  water  ' 

only  communicate  by  a  single  drop,  the  liquid  in  the  tube 
increases  in  bulk,  and  rises  in  the  tube,  as  if  the  bladder  had 
been  immersed  in  the  water;  but  the  drop  becomes  gradually 
smaller,  till  after  an  hour  or  two,  a  complete  separation  takes 
place,  and  the  drop  tears  itself  away  from  the  water.(2) 

If  the  cause  of  the  change  of  volume  in  this  experiment  were 
the  unequal  resistance  which  the  bladder  opposes  to  the  passage 
of  the  two  liquids  with  equal  attraction  (equal  force)  on  both 
sides,  the  phenomenon  just  described  would  be  inexplicable ;  for 
a  resistance  can  no  doubt  impede,  but  is  not  capable  of  producing 
motion.  But  we  see,  that  the  water  in  this  experiment  is  raised 
to  a  higher  level,  and  moreover,  the  tearing  asunder  of  the  drop  can  only  be  the 
effect  of  a  powerful  attraction,  residing  in  the  substance  of  the  bladder. 

(')  With  respect  to  the  theory,  that,  when  a  saline  solution  is  mixed  with  pure 
water,  if  the  two  liquids  are  separated  by  a  membrane,  particles  of  salt  alone  pass 
through  the  pores  of  the  bladder  to  the  water,  and  particles  of  water  alone  to  the  brine, 
the  following  experiments  may  throw  some  light  on  the  question.  For  the  sake  of 
greater  accuracy,  the  results  were  determined  by  weighing.  The  apparatus,  Fig.  3,  was 
used.  The  tube  contained  8'67  grammes  of  saturated  brine,  in  which  were  2'284  gram- 
mes of  salt  and  6'38  of  water.  After  24  hours  it  had  gained  1'79  grammes  in  weight 
and  it  now  contained  only  0-941  grammes  of  salt.  It  had  therefore  lost  1-343  grammes 
ot  salt,  and  gained  3'13  of  water.  According  to  the  above  theory,  1  atom  of  salt  and 

[2]  If  we  pour  into  a  tube,  £  of  an  inch  wide,  and  closed  with  bladder  as  much 
mercury  as  covers  the  surface  of  the  bladder,  then  fill  it  with  brine,  and  place  it  in 
pure  water,  the  volume  of  the  liquid  in  the  tube  increases  exactly  as  if  the  mercury 
were  not  there.  J 

*  The  nature  of  the  membrane  has  an  important  influence. 
T  Experiment  with  bladder,  and  with  caoutchouc 

4 


26  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

If  the  moistening  of  solid  bodies  by  liquids  be  the  effect  of  a  chemical  attraction 
the  force  of  which  is  different  in  dissimilar  liquids,  it  follows  that,  when  a  porous 
body  is  saturated  with  a  liquid,  and  brought  in  contact  with  a  second  liquid,  which 
has  a  stronger  attraction  for  its  substance  than  the  first  has,  then  the  liquid  must  be 
displaced  from  the  pores  by  the  second,  even  in  the  absense  of  hydrostatic  pressure, 
and  this,  whether  the  two  liquids  be  miscible  or  not.* 

We  may  suppose  that  the  attraction  of  the  second  liquid,  of  more  powerful  affi- 
nity, which  displaces  the  other,  is  equal  to  the  pressure  of  the  column  of  mercury 
required  to  force  the  latter  through  Hie  porous  substance. 

If  we  tie  over  one  end  of  a  cylindrical  tube  with  a  very  thin  membrane,  saturated 
with  concentrated  brine  by  steeping  24  hours,  and  if  we  dry  the  outer  surface  of 
the  membrane  carefully  with  bibulous  paper,  and  now  pour  a  few  drops  of  pure 
water  into  the  tube  so  as  just  to  cover  the  inner  surface  of  the  membrane,  the  outer 
surface  is  seen  in  a  few  moments  to  be  covered  with  minute  drops  of  brine  ;  that  is, 
brine  flows  out  of  the  pores  of  the  bladder. 

A  thick  ox-bladder,  saturated  with  oil,  exhibits  the  same  phenomenon  in  contact 
with  water.  The  oil  is  expelled  from  the  pores  of  the  bladder  by  the  water,  which 
occupies  its  place. 

When  the  bladder  is  brought  in  contact  with  pure  water,  it  takes  up  a  certain 
quantity  of  that  liquid.  If  its  pores  are  previously  filled  with  brine,  and  if  we  cover 
one  side  of  it  with  pure  water,  the  water  mixes  with  the  brine  in  the  pores  of  the 
bladder ;  and  on  the  side  next  the  water  there  is  formed  a  diluted  brine,  which, 
being  in  contact  with  a  stratum  of  pure  water,  mixes  with  it,  and  in  this  way  the 
successive  strata  of  water  receive,  from  the  bladder  outwards,  a  certain  quantity  of  salt. 

In  the  interior  of  the  bladder,  there  are  formed  in  like  manner,  towards  the  outer 
surface,  mixtures  of  unequal  saline  strength.  If  we  suppose  the  bladder  to  consist 
of  several  strata,  all  these  strata  receive,  from  the  surface  in  contact  with  the  water,  a 
certain  quantity  of  water ;  the  outer  stratum,  in  contact  with  the  air,  receives  least, 
and  is  the  most  highly  charged  with  salt. 

The  cause  of  mixture  is  the  cheminal  affinity  of  the  salt  for  the  newly-added 
particles  of  water  ;  this  affinity  is  equal  on  both  sides,  but  the  attraction  of  the  sub- 
stance of  the  bladder  is  stronger  for  the  more  aqueous  or  less  saline  liquid,  than  for 
the  more  concentrated.  In  consequence  of  this  difference  in  the  attraction  of  the 
liquids  for  the  substance  of  the  bladder,  a  part  of  the  mixture  is  displaced  from  the 
bladder ;  the  less  saline  liquid  te-kes  the  place  of  the  more  saline  ;  a  part  of  the 
latter  is  expelled,  and,  with  it,  a  part  of  that  water  which  has  been  added  to  the 
outer  stratum  by  mixture.  Brine  and  water  flow  out  in  the  direction  of  least  resist- 
ance. The  efflux  towards  the  side  on  which  the  pure  water  was  poured  is  prevented 
by  the  more  watery  liquid  for  the  substance  of  the  bladder. 

If  we  remove  from  the  outer  surface  of  the  bladder  the  displaced  saline  liquid 
(which  has  been  mixed  with  some  water,)  and  put  stronger  brine  in  its  place,  and 
if  on  the  opposite  side  we  remove  the  very  diluted  solution,  replacing  it  by  a  still 
more  diluted  one,  the  same  process  is  repeated.  There  arises  a  permanent  differ- 
ence, and  a  state  of  mixture  and  efflux  continues  till  the  liquids  on  the  opposite 
surfaces  of  the  bladder  have  the  same,  or  very  nearly  the  same,  composition. 

If  we  suppose,  that  the  two  liquids  moisten  the  bladder  unequally,  it  follows, 

*  One  liquid  expels  another  from  a  membrane. 

15  atoms  of  water  must  have  moved  past  each  other;  but  this  is  impossible,  siace  1 
atom  of  salt  requires  18  atoms  of  water  for  solution,  (10  parts  of  salt  to  27  of  water.) 
The  weight  of  the  pure  water  in  the  outer  vessel  was  19'26  grammes ;  consequently, 
the  weight  of  the  brine  was  to  that  of  the  pure  water  as  1 :  2'22.  In  another  experi- 
ment, in  which  the  weight  of  the  brine  in  the  tube  was  to  that  of  the  water  outside,  as 
1  :  7'98 ;  the  tube  gained  0*822  grammes  in  weight ;  the  liquid  in  the  tube  contained 
at  first  0-947  grammes  of  salt ;  and  24  hours  after, 0'148  grammes:  hence,  1'621  grammes 
of  water  had  entered,  while  0'799  grammes  of  salt  had  passed  out.  For  1  atom  of  salt, 
which  passed  from  the  tube  with  brine  to  the  vessel  with  water,  there  passed  from  the 
latter  to  the  former  rather  more  than  13  atoms  of  water ;  (for  58'6  parts,  or  1  atom  of 
•alt,  118  parts  of  water.) 


ATTRACTION  OF  LIQUIDS  FOR  MEMBRANES.  27 

that  in  addition  to  the  chemfcal  attraction  which  the  dissimilar  particles  of  the 
liquids  have  for  each  other,  a  new  cause,  namely,  the  strong  attraction  of  one  of 
them  for  the  suhstance  of  the  partition,  is  introduced,  which  accelerates  their  motion 
or  passage,  and  must  have  this  effect,  that  one  of  them  flows  out  in  larger  quantity, 
in  the  same  time,  than  the  other. 

The  experiments  (Fig.  3)  elucidate  this  process,  and  show  besides,  that  the 
exchange  of  the  two  liquids  on  both  sides  of  the  bladder  is  essentially  determined 
bf  their  unequal  specific  gravities.*  As  long  as  the  difference  in  their  composition 
(which  may  here  be  measured  by  the  specific  gravity)  is  very  great,  the  change  of 
volume  (increase  of  one  and  decre.ase  of  the  other)  takes  place  rapidly  ;  but  at 
last,  when  this  difference  becomes  very  small,  the  liquids  mix  without  further 
visible  change  of  volume,  obviously,  because  the  attraction  of  the  bladder  to  h; 
mixtures  on  the  opposite  sides  does  not  perceptibly  differ,  although  the  specific 
gravities  are  still  somewhat  unequal. 

In  the  ultimate  result,  the  action  of  dissimilar  liquids  on  the  substance  of  animal 
tissues,  in  consequence  of  which  their  mixture  is  attended  with  a.  change  of  volume, 
appears  to  be  equivalent  to  a  mechanical  pressure,  which  is  stronger  from  one  side 
than  from  the  other.t  p-  g 

J  If  the  tube  (Fig.  9,)  which  is  closed  with  bladder  at  its 
wide  opening,  be  filled  with  brine  to  the  mark  a,  if  so 
much  mercury  be  then  poured  into  the  narrow  vertical 
part  as  by  its  pressure  to  cause  brine  to  begin  to  flow  out 
in  fine  drops  from  the  pores  of  the  bladder,  and  if  now, 
after  removing  so  much  of  the  mercury  that  the  efflux  is 
no  longer  visible,  we  place  the  apparatus  in  a  vessel  with 
pure  water,  colored  blue,  as  in  the  figure,  the  mercury  does 
not  change  its  level ;  and  when,  after  one  or  two  hours, 
we  carefully  remove  the  tube  from  the  water,  we  find  that 
in  the  upper  part  of  the  wide  end  of  the  tube,  which  con- 
tained colorless  brine,  a  dark  blue  stratum  has  been  formed, 
which  floats  on  a  colorless  liquid.  After  a  longer  time,  the 
blue  color  spreads  gradually  downwards,  till  at  last  the 
brine  acquires  a  uniform  blue  tint. 

It  will  readily  be  perceived,  that  the  two  liquids  here  mix, 
as  if  no  pressure  had  been  applied  to  the  brine,  for  a 
mechanical  pressure  exerts  no  influence  on  the  mixture ; 
but,  in  consequence  of  the  pressure,  the  mixture  takes 
place  without  change  of  volume.  The  mechanical  pres- 
sure which  the  water,  in  virtue  of  its  stronger  affinity  for 
the  bladder,  exerts  on  the  brine  in  the  pores  of  the  bladder,  is  held  in  equilibrium 
by  the  column  of  mercury,  and  the  result  is  that  exactly  as  much  brine  flows 
out  as  water  flows  in. 

§  Let  us  suppose  the  column  of  mercury  to  be  removed,  and  the  rise  of  the 
brine  in  the  narrow  tube  is  explained  at  once.  If  we  close  a  short  tube,  filled 
with  alcohol  or  brine,  with  bladder  at  both  ends  (an  arrangement  which  may 
represent  a  cell,)  and  suspend  it  in  a  vessel  of  pure  water,  both  surfaces  of  the 
bladder  become  convex  outwards  ;  they  swell,  but  without  bursting.  As  soon  as 
the  pressure,  gradually  increasing  by  the  influx  of  water  into  the  interior  of  the 
tube,  is  sufficient  to  keep  in  equilibrium  the  affinity  of  the  water  for  the  bladder, 
and  consequently  its  further  influx,  the  exchange  goes  on,  for  the  future,  without 
change  of  volume. 

Most  porous  bodies  exhibit  the  phenomena  described  in  the  preceding  pages,  if 
their  pores  are  so  minute  that  a  feeble  hydrostatic  pressure  is  not  propagated 

*  Mixture  is  essentially  determined  by  the  unequal  density  of  the  liquids. 

o     ositeSS?1  °f  tw°  ll(Julds  on  ammal  tissues  equivalent  to  a  mechanical  pressure,  unequal  on 
t  Experiment  to  show  that  an  external  pressure  prevents  change  of  volume. 


28  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

through  them.*  These  phenomena  may  be  produced  with  clay  cells  (J)  (such  as 
are  used  for  galvanic  apparatus ;)  with  the  lining  membrane  of  the  pods  of  peas 
and  beans  ;  with  the  fine  inner  bark  of  trees  ;  with  the  skin  of  grapes,  of  potatoes, 
of  apples  ;  with  the  inner  membrane  of  the  capsules  of  bladder  senna,  &c. ;  but 
animal  tissues  surpass  all  others  in  efficacy.  Besides  their  unequal  affinity,  they 
have  an  unequal  absorbent  power  for  dissimilar  liquids,  by  which  their  action  in 
causing  change  of  volume  during  mixture  is  strengthened. 

When  a  tube,  closed  with  bladder,  and  filled  with  water,  is  immersed  in  alcohol 
or  brine,  there  is  produced  at  all  points,  where  the  brine  or  the  alcohol  comes  in 
contact  with  bladder  saturated  with  water,  a  change  in  the  properties  of  the  bladder.! 
When,  in  the  open  pores,  the  alcohol  or  brine  mixes  with  the  water  already  there, 
the  absorbent  power  of  the  bladder  for  the  water  is  diminished ;  a  smaller  volume 
of  the  mixture  is  retained  than  of  pure  water ;  that  is  to  say,  water  flows  out  in 
the  direction  of  the  alcohol  or  brine.  This  efflux  is  accompanied  by  a  change  in 
the  volume  of  the  substance  of  the  bladder,  for  that  side  of  it  which  is  towards 
the  alcohol  or  the  brine  contracts  or  shrinks. 

The  opposite  surfaces  of  an  animal  membrane,  in  contact  with  dissimilar  liquids, 
for  which  they  have  unequal  absorbent  power,  are  in  an  unequal  state  of  contraction. 
This  condition  is  permauent,  as  long  as  the  liquids  do  not  change  in  their  proper- 
ties ;  but  it  ceases,  in  consequence  of  mixture,  and  is  again  restored,  when,  by  mean? 
of  the  change  of  place  in  both  the  liquids  which  are  in  contact  with  the  opposite  sur- 
faces of  the  bladder,  the  original  or  any  other  permanent  inequality  or  difference 
of  properties  is  produced. 

In  all  cases  where  a  permanent  change  in  the  volume  of  two  liquids,  separated 
by  a  membrane,  is  observed  during  their  mixture,  it  is  always  accompanied  by  a 
permanent  difference  in  the  nature  or  properties  of  the  two  liquids ;  and  from  this 
it  follows,  that  the  molecules  of  the  animal  membrane  must  be,  during  the  mixture, 
in  an  alternate  state  of  contraction  and  swelling,  or  dilatation  ;  that  is,  in  a  continual 
motion.'jf. 

From  what  has  been  stated,  it  appears  that  the  change  of  volume  of  two  miscible 
liquids,  separated  by  a  membrane,  is  determined  by  the  unequal  capacity  of  being 
moistened,  or  the  unequal  attraction  of  the  membrane  for  these  liquids.  The  une- 
qual absorbent  power  of  the  membrane  for  these  liquids  depends  on  the  dissimilar 
nature  of  the  liquids  or  of  the  substances  dissolved  in  them.  An  unequal  proportion 

(')  I  consider  it  of  sufficient  importance  to  state  here  that  porous  clay  also  takes  up 
unequal  volumes  of  brine  and  water.  In  special  experiments  made  on  this  subject, 
cells  of  clay  (moderately  ignited  porcelain  biscuit)  were  laid  for  24  hours  in  pure  water, 
then  carefully  dried  externally  with  bibulous  paper,  and  the  increase  in  weight,  that  is, 
the  weight  of  the  absorbed  water,  carefully  determined.^  The  clay  was  then  carefully 
dried,  laid  for  24  hours  in  brine,  and  the  weight  of  the  absorbed  brine  determined  in 
like  manner.  In  a  second  series  of  experiments,  the  clay  cells  were  steeped  in  water 
and  brine,  and  placed  in  the  receiver  of  the  air-pump,  under  a  pressure  of  8  lines  of 
mercury  (3  of  an  inch)  for  24  hours. 

Under  the  ordinary  pressure,  and  in  air  the  cells  absorbed — 

Weight.  Volume. 

Water.     Brine.       Water.     Brine 

100  parts  of  clay  cell I.— 15'4      14'6        15'4      12'2 

II.— 11-8      11-6        11-8        9-7 

In  vacuo  the  cells  of  clay  absorbed — 

Weight.  Volume. 

Water.     Brine.        Water.      Brine. 

100  parts  of  clay  cell  absorbed     I.— 16-5      16-8        16*5      14*0 

II.— 13-8      13-8        13-8      11-5 

*  Porous  bodies  in  general  exhibit  similar  phenomena. 

t  Bladder  shrinks  in  contact  with  brine  or  alcohol. 

J  Change  of  volume  in  two  liquids,  separated  by  membrane,  is  accompanied  by  continual 
tnotion  in  the  particles  of  the  membrane ;  and  depends  on  the  unequal  attraction  of  the  membrane 
for  the  liquids. 

$  Amount  of  liquids  absorbed  by  porous  baked  clay. 


EXAMPLES  OF  CHANGE  OF  VOLUME  IN  LIQUIDS.  29 

of  the  same  dissolved  matters  (unequal  concentration,)  acts  in  many  cases,  just  as 
if  the  liquids  contained  dissimilar  substances. 

Although  the  experiments  hitherto  instituted,  and  the  results  obtained  by  FISCHER 
(who  first  observed  these  phenomena,)  MANGUS,  DUTROCHET,  and  others,  admit  of 
no  comparison,  since  the  apparatus  used  by  them  showed  only  relative  change  of 
volume,  yet  a  knowledge  of  some  of  these  results  is,  nevertheless,  of  importance. 

When  the  two  liquids  are,  diluted  sulphuric  acid  (of  sp.  g.  1-093)  and  water,  the 
acid,  at  50°  F.,  increases  in  volume  ;  but  if  the  acid  have  the  specific  gravity  1-054, 
the  volume  of  the  water  increases,* 

Diluted  tartaric  acid  (11  parts  of  the  crystalized  acid  and  89  of  water)  and  water 
mix  through  a  bladder  without  change  of  volume  ;  with  more  than -11  per  cent,  of 
acid,  the  volume  of  the  acid  increases ;  with  less  that  of  the  water. 

Solutions  of  animal  gelatine,  gum,  sugar,  and  albumen  increase  in  volume  when 
separated  by  a  bladder  from  water ;  and  the  increase  of  volume  in  these  different 
solutions,  although  of  the  same  specific  gravity,  is  very  different  indeed.  When 
the  specific  gravity  ia  1-07,  the  increase  in  volume  of  the  solution  of  gelatine 
amounts  to  3,  that  of  solution  of  gum  to  5,  of  sugar  11,  of  albumen  12.  When  a 
solution  of  sugar  (1  part  of  sugar  to  16  of  water)  is  separated  by  a  bladder  from 
water,  it  increases  in  volume ;  but  if  we  add  1  part  of  oxalic  acid  to  the  sugar,  the 
water,  on  the  contrary,  increases  in  volume.  If  the  amount  of  sugar  in  the  solution 
be  doubled,  the  liquids  mix  without  change  of  volume.  A  solution  of  sugar,  separa- 
ted by  bladder  from  one  of  oxalic  acid,  rises,  in  the  same  time,  3  times  higher  than 
when  separated  from  water.  (DUTROCHET.) 

From  these  experiments  we  obtain,  as  a  universal  result  (which,  however,  requires 
confirmation,)  that  an  animal  membrane  possesses  a  less  power  of  absorption  for 
solution  of  albumen  than  for  all  other  organic  substances  :t  and  that  a  small  amount 
of  mineral  or  organic  acids  increases  the  power  transudation  of  water  as  well  as  of 
the  solutions  of  many  organic  substances.^1) 

The  rapidity  of  mixture  of  two  liquids,  separated  by  a  membane,  depends  on 
the  thicknes  of  the  membrane,  and  stands  in  direct  proportion  to  the  velocity  with 
which  the  mixture  formed  in  the  pores  and  on  both  surfaces  of  the  bladder  changes 
its  place,  and  the  original  difference  in  the  quality  of  the  two  liquids  is  renewed. § 

||  If  we  suppose  a  tube,  formed  of  a  membrane  (an  intestine,  for  example,)  and 
filled  with  water,  and  if  we  assume  that  a  current  of  saline  solution  flows  round 
this  tube,  in  consequence  of  a  mechanical  force,  the  increase  of  volume  of  the  brine 
(the  passage  into  it  of  a  certain  amount  of  water)  will  be  effected  in  a  far  shorter 
time  than  if  the  brine  were  not  in  motion. 

The  velocity  of  transference  will  diminish  with  the  amount  of  difference  in 
properties  between  the  two  liquids  (the  different  amount  or  per  centage  of  salt  ;)^[ 
it  will  be  greatest  at  first,  and  diminish  as  the  dilution  of  the  brine  increases,  in 
proportion,  that  is  to  say,  as  water  is  transferred  from  the  contents  of  the  tube  to 
the  liquid  without. 

The  greatest  effect,  therefore,  must  occur  and  be  permanent,  when  the  water 
transferred  to  the  brine  is  continually  again  removed  from  it,  that  is,  when  the  con- 
centration of  the  brine  is  kept  uniform.**  To  this  end,  if  we  suppose  the  membrane 

(!)In  order  not  to  be  misled  in  such  experiments,  we  must  avoid  the  employment  of  all 
those  liquids  which  alter  the  membrane  in  its  chemical  properties.  Such  are,  for  exam- 
ple, acids  of  a  certain  concentration,  nitrate  of  silver,  salts  of  lead,  chloride  of  gold,  chlo- 
ride of  tin,  chromic  acid,  bichromate  of  potash,  taunic  acid,  &c.  Even  in  water,  the 
properties  of  membranes  generally  undergo  a  change  after  some  days,  they  then  propa- 
gate a  far  weaker  hydrostatic  pressure  through  their  pores,  and  are  no  longer  fit  for 
such  experiments. 

*  Examples  of  change  of  volume ;  in  acids,  and  neutral  organic  substances,  according  to 
DUTROCHET 

t  Membranes  have  a  feeble  power  of  absorbing  solution  of  albumen. 
t  Effect  of  adding  acids. 

j  Causes  which  influence  rapidity  of  mixture. 
f|  Motion  of  one  of  the  liquids. 
fi  Difference  in  properties  of  the  two  liquids. 
**  Effect  of  the  continual  removal  of  the  transferred  liquid  analagous  to  suction. 


PO  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

to  be  difficultly  permeable  for  one  liquid,  while  the  other  is  easily  taken  up  into  its 
pores,  and  if  we  reflect,  that  this  second  liquid,  on  entering  into  the  pores  of  the 
bladder,  in  virtue  of  the  attraction  of  their  walls  for  it,  acquires  a  certain  velocity 
which  permits  it  to  pass  beyond  the  extremitiss  of  the  canal  or  the  pores,  so  as  to 
entirely  fill  the  pores,  and  to  come  in  direct  contact  with  the  liquid  on  the  outside 
of  the  pores,  it  follows,  that,  when  this  second  liquid  moves  past  the  poses  with  a 
certain  velocity,  the  absorbed  liquid  must  follow  it  during  the  mixture,  and  there 
must  take  place  a  rapid  transference  of  the  second  liquid  to  the  first,  a  true  suction 
as  if  by  a  pump. 

The  animal  body  is  an  example  of  an  apparatus  of  this  kind  in  the  most  perfect 
form.*  The  blood  vessels  contain  a  liquid,  for  which  their  walls  are,  in  the 
normal  state,  far  less  permeable  than  for  all  the  other  fluids  of  the  body.  The 
blood  moves  in  them  with  a  certain  velocity,  and  is  kept  at  all  times  in  a  nearly 
uniform  state  of  concentration  by  a  special  apparatus,  namely,  the  urinary 
organs. 

The  whole  intestinal  canal  is  surrounded  with  this  system  of  blood  vessels,  and 
all  the  animal  fluids,  in  so  far  as  they  are  capable  of  being  taken  up  by  the  parietes 
of  the  intestinal  canal,  and  of  the  blood  vessels  situated  around  it,  are  rapidly 
mixed  with  the  blood.t  The  volume  of  the  blood  increases,  if  no  compensation 
is  effected  by  means  of  the  kidneys :  and  the  intestine  is  emptied  of  the  liquids 
contained  in  it.  The  intestinal  glands,  through  which  this  transference  is  effected, 
and  each  of  which  represents  a  similar  apparatus  of  suction,  contain,  within  them, 
two  systems  of  canals, — blood  vessels  and  lacteals;  the  blood  vessels  are  placed 
next  to  the  external  absorbent  surface,  the  lacteals  chiefly  occupy  the  central  pait 
of  the  gland.  The  liquids  circulating  in  these  two  systems  have  very  unequal 
velocities,  and  as  the  blood  moves  much  faster  in  the  blood  vessels,  we  perceive  how 
it  happens,  that  the  fluids  of  the  intestine  are  chiefly  (in  quantity  and  in  velocity) 
taken  up  into  the  circulation. 

The  difference  in  the  absorbent  power  of  the  parietes  of  the  intestinal  canal  for 
liquids  which  contain  unequal  amounts  of  dissolved  matters,  is  easily  observed  in 
the  effects  produced  on  the  organism  by  water  and  saline  solution s.J 

If  we  take  while  fasting,  every  ten  minutes,  a  glass  of  ordinary  spring  water 
the  saline  contents  of  which  are  much  less  than  those  of  the  blood,  there  occurs, 
after  the  second  glass  (each  glass  containing  4  ounces,)  an  evacuation  of  colored 
urine,  the  weight  of  which  is  very  nearly  equal  to  that  of  the  first  glass  ;  and  after 
taking,  in  this  way,  20  such  glasses  of  water,  we  have  had  19  evacuations  of  urine, 
the  last  of  which  is  colorless,  and  contains  hardly  more  saline  matter  than  the 
spring  water. 

If  we  make  the  same  experiment  with  a  water,  containing  as  much  saline  matter 
as  the  blood  (£  to  1  per  cent,  of  sea  salt,)  there  is  no  unusual  discharge  of  urine, 
and  it  is  difficult  to  drink  more  than  three  glasses  of  such  water.  A  sense  of 
repletion,  pressure,  and  weight  of  the  stomach  point  out,  that  water  as  strongly 
charged  with  saline  matter  as  the  blood  requires  a  longer  time  for  its  absorption 
into  the  blood  vessels. 

Finally,  if  we  drink  a  solution  containing  rather  more  salt  than  the  blood,  a 
more  or  less  decided  catharsis  ensues. § 

The  action  of  solution  of  salt  is  of  three  kinds,  according  to  the  proportion  of 
salt.  Spring  water  is  taken  up  into  the  blood  vessels  with  great  rapidity  ;  while 
these  vessels  exhibit  a  very  small  power  of  absorption  for  water  containing  the 
same  proportion  of  salt  as  the  blood  does ;  and  a  still  more  strongly  saline  solu- 
tion passes  out  of  the  body — not  through  the  kidneys,  but  through  the  intestinal 
canal. 

Saline  solutions  and  water,  given  in  the  form  of  enemata,  exhibit  similar 
phenomena  in  the  rectum. ||  Pure  water  is  very  rapidly  absorbed,  and  excreted 

*  This  occurs  in  the  animal  body. 

t  Absorption  of  the  liquids  of  the  intestines  into  the  blood, 
j  Effects  produced  by  drinking  water  and  saline  solutions. 

*  Solution  containing  more  salt  than  the  blood. 
o  Enemata  of  water  and  saline  solutions. 


INFLUENCE  OF  THE  MEMBRANES  ON  THE  SECRETIONS.  31 

through  the  urinary  passages.  If  we  add  to  the  water  colored  or  odorous  matters, 
these  appear,  more  or  less  changed  in  the  urine.  When  a  small  quantity  of 
ferrocyanide  of  potassium  is  added,  its  presence  in  the  urine  is  very  soon  detected 
by  chloride  of  iron,  which  forms  with  it  Prussian  blue.  Of  concentrated  solutions 
far  less  is  absorbed  in  the  same  time,  than  of  diluted;  in  most  cases  they  mix  with 
solid  matters  collected  in  the  rectum,  and  are  expelled  in  the  form  of  a  watery 
dejection. 

All  salts  do  not  act  alike  in  this  respect.  In  equal  doses,  the  purgative  action  of 
Glauber  salt  and  Epsom  salt  is  far  stronger  than  that  of  sea  salt;  and  their  power 
of  being  absorbed  by  animal  membranes  appears  to  be  in  the  inverse  ratio  of  this 
effect.  It  is  hardly  necessary,  particularly  to  point  out  that  an  explanation  of  the 
action  of  purgatives  in  general  cannot  be  included  in  the  above-described  action  of 
saline  solutions  on  the  organism.  The  example  which  has  been  given  is  intended 
to  illustrate  a  physical  property  common  to  a  large  number  of  salts,  and  apparently 
of  the  nature  of  the  acid  or  base  of  the  salt ;  for  chloride  of  calcium,  chloride  of 
magnesium,  bitartrate  of  potash,  tartrate  of  potash  and  soda,  phosphate  of  soda,  and 
certain  doses  of  tartar  emetic,  show  the  same  action  as  sea  salt,  Glauber  salt,  and 
Epsom  salt,  although  the  bases  and  acids  in  these  different  salts  are  not  the  same. 

Solutions  of  cane  sugar,  grape  sugar,  sugar  of  milk,  and  gum,  exhibit,  when 
separated  from  water  by  an  animal  membrane,  phenomena  similar  to  those  exhibited 
by  the  above-named  solutions  of  mineral  salts,  without  causing  in  the  living  body  a 
purgative  action,  when  of  equal  concentration.  The  cause  of  this  difference 
may  be  that  the  mineral  salts,  in  their  passage  through  the  intestinal  canal,  and 
through  the  blood,  are  not  essentially  altered  in  their  composition,  while  these 
organic  substances,  in  contact  with  the  parietes  of  the  stomach,  and  under  the 
influence  of  the  gastric  juice,  suffer  a  very  rapid  change,  by  which  the  action  which 
they  have  out  of  the  body  is  arrested. 

Since  the  chemical  nature  and  the  mechanical  character  of  mebranes  and  skins 
exert  the  greatest  influence  on  the  distribution  of  the  fluids  in  the  animal  body, 
the  relations  of  each  membrane  presenting  any  peculiarity  of  structure,  or  of  the 
different  glands  and  systems  of  vessels,  deserve  to  be  investigated  by  careful 
experiment  ;*  and  it  might  very  likely  be  found  that  in  the  secretion  of  the  milk, 
the  bile,  the  urine,  the  sweat,  &c.,  the  membranes  and  cell-walls  play  a  far  more 
important  part  than  we  are  inclined  to  ascribe  to  them ;  that  besides  their  physical 
properties,  they  possess  certain  chemical  properties,  by  which  they  are  enabled  to 
produce  decompositions  and  combinations,  true  analyses  ;  and  if  this  were  ascer- 
tained, the  influence  of  chemical  agents,  of  remedies,  and  of  poisons  on  those 
properties,  would  be  at  once  explained. 

The  phenomena  described  in  the  preceding  pages  are  observed,  not  in  the 
gelatinous  tissues  alone,  but  also,  apparently,  in  many  other  structures  of  the  animal 
body,  which  cannot  be  reckoned  as  belonging  to  that  class.t 

If  we  tie  moist  paper  over  the  open  end  of  a  cylindrical  tube,  and,  after  pouring 
in  above  the  paper  white  of  egg  to  the  height  of  a  few  lines,  place  that  end  of 
the  tube  in  boiling  water,  the  albumen  is  coagulated,  and  when  the  paper  is  removed, 
we  have  a  tube  closed  with  an  accurately  fitting  plug  of  coagulated  albumen, 
which  allows  neither  water  nor  brine  to  run  through.;};  If  the  tube  be  now  filled 
to  one-half  with  brine,  and  immersed  in  pure  water,  as  in  Fig.  4,  the  brine  is  seen 
gradually  to  rise ;  and  in  three  or  four  days  it  increases  by  from  |  to  £  of  its 
volume,  exactly  as  if  the  tube  had  been  closed  with  a  very  thick  membrane 

Influence  of  the  cutaneous  evaporation  on  the  motion  of  the  fluids  of  the 

animal  body. 

When  a  tube  about  30  inches  long,  bent  in  the  form  of  a  knee,  and  widened  at 
one  end,  is  tied  over  at  that  end  with  a  piece  of  moist  ox-bladder,  the  bladder  now 

*  Influence  of  membranes  on  secretions. 

t  These  phenomena  not  confined  to  the  gelatinous  tissues. 

t  Coagulated  albumen  acts  like  a  thick  membrane. 


MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 


thoroughly  dried,  and  the  tube  filled  with  mercury  and  inverted,  so  that  the  open, 
narrow  end  stands  in  a  cup  of  mercury,  the  mercury  in  the  tube  falls  to  about  27 
inches  (Hessian,)  and  remains,  if  the  bladder  have  no  flow,  at  that  height,  rising  and 
falling  as  the  mercury  does  in  a  barometer. 

No  air  passes  through  the  dry  bladder  into  the  Torricellian  vacuum  thus  pro- 
duced. When,  by  proper  manipulation,  we  have  allowed  to  pass  out  as  much  as 
can  be  removed  of  the  air  still  contained  in  the  tube,  we  have,  in  this  arrangement, 
a  barometer,  containing  no  more  air  than  would  be  found  in  one  made  with  a 
similar  tube  hermetically  sealed  at  the  wide  end,  provided  the  mercury  in  the 
latter  had  not  been  boiled  in  the  tube  to  expel  the  last  traces  of  air.  By  the 
desiccation  of  the  bladder,  its  pores,  which  allowed  a  passage  to  water,  brine,  oil, 
or  even  mercury,  have  obviously  been  closed  by  the  adhesion  of  the  successive 
layers  of  membrane,  which  perhaps  cross  each  other,  so  that  the  bladder  is  not 
more  permeable  for  the  particles  of  air  than  a  slice  of  horn  of  the  same  thickness. 


p> 


If  we  introduce  water  into  the  tube  in  the  posi- 
tion, Fig.  10,  to  the  line  marked  6,  and,  after  fill-  Fig.  11. 
ing  the  narrow  part  of  the  tube  with  mercury, 
invert  it  in  a  vessel  of  mercury,  Fig.  11,  we 
observe  a  number  of  minute  bubbles  of  air  passing 
through  the  moist  bladder  into  the  tube.  The 
mercury  falls  to  a  certain  point,  which  is  higher 
or  lower  according  to  the  thickness  of  the  bladder; 
it  stands  at  a  lower  level  with  a  thin  membrane 
than  with  a  thick  one.  When  a  single  layer  of 
ox-bladder  is  used,  it  falls  to  12  inches  (above 
the  level  of  the  mercury  in  the  vessel ;)  with  a 
double  layer  it  stands  at  from  22  to  24  inches. 

If  we  take  care  to  allow  the  water  standing 
above  the  mercury  to  enter  the  wide  part  of  the 
tube,  so  that  the  bladder  is  kept  at  all  times 
covered  with  water,  the  mercury  remains  stationary 
at  the  same  level.  If,  for  example,  it  stood  at 
12  inches,  it  remains  there,  although  the  quantity 
of  water  is  constantly  diminishing  by  evaporation 
from  the  bladder ;  and  it  maintains  its  level,  even 
after  all  the  water  has  disappeared. 

The  height  of  the  mercury  in  the  narrow  tube  is  an  exact  measure  of  the  pres- 
sure acting  on  the  surface  of  the  bladder.  The  pressure  in  the  inside  of  the  tube 
is  less  than  the  existing  pressure  of  the  atmosphere  outside  by  the  height  of  that 
column  of  mercury. 

This  difference  of  level  between  the  mercury  in  the  vessel  and  that  in  the  tube 
is  the  limit  of  the  pressure,  under  which  air  passes  into  the  water  through  the 
pores  of  the  bladder ;  or  under  which  the  molecules  of  water  in  the  pores  are 
displaced  by  the  molecules  of  air. 

If  we  fill  the  tube  entirely  with  water,  and  place  the  narrow  end  in  mercury, 
while  the  wide  end,  closed  with  bladder,  is  exposed  to  the  air,  the  mercury  rises 
in  the  narrow  limb,  and  at  last  reaches  a  point,  identical  with  that  to  which  it  fell 
in  the  preceding  experiment.  For  each  specimen  of  bladder,  according  to  its 
thickness,  the  level  to  which  the  mercury  reaches  is  of  course  different. 

When  the  diameter  of  the  wide  part  of  the  tube,  which  is  closed  with  bladder, 
is  12  millimetres,  and  that  of  the  narrow  tube  1  millimetre,  the  mercury  rises, 
with  ox-bladder,  according  to  the  temperature  and  the  hygrometric  condition  of  the 
air,  to  from  22  to  65  millimetres  in  one  hour. 

The  cause  of  the  rise  of  the  mercury  in  this  experiment  hardly  requires  a  special 
explanation. 

The  bladder  is  penetrated  with  water,  covered  on  one  side  with  water,  and  on 
the  other  in  contact  with  a  space  (the  air)  not  saturated  with  aqueous  vapour 
The  water  contained  in  the  pores  of  the  side  of  the  bladder  turned  towards  the  air 


ATMOSPHERIC  PRESSURE  ON  THE  LEVEL  OF  THE  MERCU.RY.         33 


evaporates :  the  space  which  it  had  occupied  in  the  pores  is  filled  with  successive 
portions  of  water  from  within,  in  virtue  of  the  attraction  of  the  substance  of  the 
pores  for  water.  The  volume  of  the  water  in  the  tube  diminishes,  and  thus  a 
vacuum  arises,  in  which  the  mercury  is  forced  to  rise  by  the  atmospheric  pressure. 
The  space  formerly  occupied  by  the  water  which  has  evaporated  is  now  filled  with 
mercury. 

When  the  mercury  has  reached  a  permanent  level,  the  external  pressure,  which 
acts  on  the  water  in  the  pores  of  the  bladder  (and  which  tends  to  displace  the  parti- 
cles of  water)  is  obviously  equal,  before  air  enters,  to  the  attraction  which  the 
substance  of  the  bladder  has  for  the  particles  of  water,  and  these  last  to  each  other. 
Were  the  attraction  less,  air  would  enter,  and  the  particles  of  water  could  not  main- 
tain their  position. 

The  rise  of  tUe  mercury,  or  its  motion  towards  the  surface  of  the  bladder,  that  is, 
towards  the  point  where  evaporation  is  going  on,  is  the  result  of  a  difference  of 
atmospheric  pressure,  determined  by  the  evaporation  of  the  water,  or  of  the  liquid 
which  penetrates  through  the  bladder,  and  by  the  absorbent  power  of  the  bladder 
for  that  liquid. 

One  chief  condition  of  the  efficiency  of  a  bladder,  in  regard  to  the  rise  of  a 
coulmn  of  liquid,  is,  that  it  is  kept  constantly  in  contact  with  the  liquid,  for  without 
this  contact  the  absorbent  power  cannot  manifest  itself. 

By  the  evaporation  a  continual  efflux  of  water,  in  the  form  of  vapour,  towards 
the  side  on  which  the  air  lies,  is  produced  ;  and  by  the  capillary  action  of  the  blad- 
der on  the  other  side,  water  is  absorbed  and  retained  with  a  force  which  counter- 
poises 12  or  more  inches  of  mercury,  according  to  the  thickness  of  the  bladder. 

Now,  since  the  rise  of  the  mercury  is  an  effect  of  the  atmospheric  pressure,  it  is 
plain,  that  the  height  to  which  the  mercury  rises,  must  depend  to  a  certain  degree 
on  the  state  of  the  barometer.* 

In  a  tube  filled  with  water,  and  closed  with  bladder,  the  absorbent  force  of  which 
is  equal  to  the  pressure  of  a  column  of  12  inches  of  mercury,  the  mercury  rises  by 
evaporation  to  the  height  of  12  inches,  as  long  as  a  column  of  12  inches  of  mercury 
can  be  sustained  by  the  external  atmospheric  pressure.  If  this  external  pressure 
fall  below  that  limit,  the  mercury  in  the  evaporation  tube  falls  to  the  same  extent, 
and  if  there  be  water  above  the  mercury,  this  water  separates  from  the  bladder. 

This  property  of  bladder,  therefore,  would  appear  unaltered  at  an  elevation 
at  which  the  barometer  should  stand  at  12  inches ;  at  a  still  greater  elevation,  on 
the  contrary,  the  liquid  would  separate  from  the  bladder. 

The  external  pressure  has  no  influence  on  the  amount  of  the  water  evaporating 
in  the  pores  of  the  bladder ;  that  amount  depends  on  the  hygrometric  state  of  the 
surrounding  air,  and  on  the  temperature.!  In  a  rarified  air, 
(provided  it  can  take  up  moisture,)  evaporation  goes  on  more 
rapidly  than  in  a  denser  air ;  and  hence  it  is  clear,  that  at 
certain  elevations,  the  effect  of  the  bladder  on  the  level  of  the 
liquid  is  more  quickly  produced  than  at  the  level  of  the  sea. 
The  amount  of  water  which  evaporates  is  directly  propor- 
tional to  the  surrounding  space,  and  to  the  temperature  and 
corresponding  tension  of  the  liquid. 

When  the  tube,  Fig.  10,  is  filled  with  water  to  6,  then 
entirely  filled  with  mercury  and  inverted  in  mercury,  the  Fig.  10. 
mercury,  as  we  have  seen,  assumes  a  fixed  level.  If  we 
now  keep  the  upper  or  wide  end  of  the  tube,  which  is  closed 
with  bladder,  immersed  in  a  vessel  of  water,  Fig.  12,  we  shall 
find,  after  a  short  time,  that  the  mercury  sinks  in  the  narrow 
tube.  If  its  level  has  been  12  inches  above  that  of  the  mer- 
cury in  the  vessel,  it  sinks  when  the  bladder  is  put  into 
water,  3  or  4  inches  for  example,  and  remains  stationary  at 
8  or  9  inches,  without  sinking  further  for  the  next  12  hours. 

*  Influence  of  the  state  of  the  barometer 

t  The  pressure  of  the  air  does  not  affect  the  amount  of  evaporation. 

5 


34  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

The  sinking  of  the  mercury  is  caused  by  water  being  forced  through  the  bladder 
into  the  tube,  in  virtue  of  the  existence  of  an  external  pressure  greater  than  the 
pressure  on  the  inside  of  the  tube. 

To  displace  the  aqueous  particles  in  the  pores  of  the  bladder  by  other  aque- 
ous particles,  requires  obviously  a  much  smaller  pressure  than  is  necessary  to  dis- 
place them  by  particles  of  air.*  In  the  one  case,  where  both  surfaces  of  the 
bladder  are  in  contact  with  the  liquid,  the  attractive  force  (that  of  the  bladder  for 
the  water  and  of  the  water  for  the  bladder)  is  equal  on  both  sides ;  but  not  so  in 
the  other  case,  where  one  side  of  the  bladder  is  in  contact  with  air.  If  the 
bladder  had  the  same  absorbent  power  for  the  particles  of  air  as  for  those  of  water, 
the  particles  of  air  and  water  would  pass  through  the  bladder  under  the  same  pres- 
sure ;  the  experiment  shows,  that  the  absorbent  power  and  permeability  of  the 
bladder  for  air  is  far  less  than  for  water.  Hence,  it  comes  to  pass,  that  when,  with 
a  given  portion  of  bladder,  in  the  apparatus  Fig.  11,  mercury  is  raised  by  evapora- 
tion to  a  heighth  of  12  inches,  less  than  12  inches  of  mercury  are  required,  in  the 
apparatus,  Fig.  1,  to  cause  water  to  pass  through  the  bladder. 

py      jo  t  When  the  tube,  (Fig.  13,)  is  filled  with  water,  closed  with  blad- 

der at  both  ends,  and  exposed  to  evaporation,  the  bladders  in  a 
short  time  become  concave,  that  is,  they  are  pressed  inwards.  As 
the  evaporation  of  the  water  through  the  moist  surfaces  of  the 
bladder  proceeds,  there  is  formed  in  the  upper  part  of  the  tube  a 
vacuum,  which  is  filled  with  aqueous  vapor,  and  which  continues  to 
increase.  The  place  of  the  water  which  evaporates  is,  as  in  the 
experiments  previously  described,  gradually  occupied  by  air,  which 
enters  the  tube  through  the  bladder. 

It  is  evident,  that  when  air  enters  the  tube,  (Fig.  13,)  the  pressure 
on  the  surface  of  the  bladder  is  equal  to  the  absorbent  force  of  that 
bladder  for  the  water.  In  the  apparatus,  Fig.  11,  with  the  same 
bladder,  the  mercury  might  have  been  raised,  in  consequence  of 
the  evaporation,  to  a  height  of  4,  6,  12,  or  more  inches,  according 
to  the  thickness  of  the  membrane. 

-  .  When  the  -longer  limb  of  the  bent  tube,  after  it  has   been 

.  14.  filled  with  water,  and  closed  at  both  ends  with  bladder,  is  placed 
in  a  vessel  containing  brine,  and  exposed  to  evaporate  in  the  air, 
as  in  Fig.  14,  it  is  plain,  that  when  the  atmospheric  pressure, 
increasing  in  consequence  of  the  evaporation  of  the  water  on  both 
the  surfaces  of  the  bladder,  reaches  the  point  at  which  the  brine 
flows  through  the  pores  of  the  bladder,  then  the  place  of  the 
water  which  evaporates  is  occupied  by  brine. 

In  fact,  when  the  brine  is  colored  blue,  we  observe,  after  a  few 
hours,  that  a  blue  stratum  forms  within  the  tube,  which  constantly 
increases,  till  at  last  the  vessel  of  brine  is  emptied,  and  the  tube 
is  entirely  filled  with  brine. 

If  the  longer  limb  be  immersed  in  bile  instead  of  brine,  the 
tube  fills  with  bile,  and  if  we  employ,  for  closing  one   end,  a 
^^^^^  membrane  rather  thinner  than  we  use  for  the  other,  from  which 

the  evaporation  takes  place,  and  then  place  the  end  with  the  thinner  membrane  in 
oil  (oil  of  marrow,)  the  tube  gradually  fills  with  oil. 

In  all  these  cases,  no  air  enters  the  tube,  which  continues  full  of  liquid,  as  it 
was  at  first. 

J  If  we  connect  the  evaporation  tube  by  collars  of  caoutchouc  with  short  bits 
of  tube  (Fig.  15,)  full  of  water,  and  tied  with  bladder  at  both  ends ;  and  if  we 
immerse  the  last  bit  of  tube  in  brine,  urine,  oil,  &c.,  all  these  cells,  and  at  last  the 


*  Water  passes  through  moist  bladder  more  easily  than  air  does. 

t  Experiments  with  a  tube  closed  at  both  ends  with  bladder :  with  one  end  in  brine,  the  tube 
b«mg  filled  with  water,  with  one  end  in  bile,  and  in  oil. 
J  Effect  of  a  s«  ries  of  short  tubes,  closed  at  both  ends  with  bladder. 


IMPORTANCE  OF  THE  CUTANEOUS  TRANSPIRATION.  35 

Fig.  15.          evaporation  tube  itself,  become  gradually  filled  with  brine,  urine, 
oil,  &c. 

*  The  most  general  expression  for  these  experiments  and  results 
is  this ;  — that  all  liquids  which  are  in  connection  with  a  mem- 
brane from  the  surface  of  which  evaporation  can  take  place,  must 
acquire  motion  towards  that  membrane. 

The  amonnt  of  this  motion  is  directly  proportional  to  the 
rapidity  of  evaporation,  and  consequently  to  the  temperature  and 
hygrometric  state  of  the  atmosphere. 

That  the  skin  of  animals,  and  the  cutaneous  transpiration,  as 
well  as  the  evaporation  from  the  internal  surface  of  the  lungs, 
exert  an  important  influence  on  the  vital  processes,  and  thereby 
on  the  state  of  health,  has  been  admitted  by  physicians  ever 

since  medicine  has  existed;  but  no  one  has  hitherto  ascertained 

precisely  in  what  way  this  happens.t 

From  what  has  gone  before,  it  can  hardly  be  doubted,  that  one  of  the  most 
important  functions  of  the  skin  consists  in  the  share  which  it  takes  in  the  motion 
and  distribution  of  the  fluids  of  the  body  4 

The  surface  of  the  body  of  a  number  of  animals  consists  of  a  covering  or  skin 
permeable  for  liquids,  from  which,  when,  as  in  the  case  of  the  lung,  it  is  in  con- 
tact with  the  atmosphere,  an  evaporation  of  water,  according  to  the  hygrometric 
state  and  temperature  of  the  air,  constantly  goes  on.§ 

If  we  now  keep  in  mind,  that  every  part  of  the  body  has  to  sustain  the  pressure 
of  the  atmosphere,  and  that  the  gaseous  fluids  and  liquids  contained  in  the  body 
oppose  to  this  pressure  a  perfectly  equal  resistance,  it  is  clear  that,  by  the  evapora- 
tion of  the  skin  and  lungs,  and  in  consequence  of  the  absorbent  power  of  the  skin 
for  the  liquid  in  contact  with  it,  a  difference  in  the  pressure  below  the  surface  of 
the  evaporating  skin  occurs.  The  external  pressure  increases,  and  in  an  equal 
degree  the  pressure  from  within  towards  the  skin.  If  now  the  structure  of  the 
cutaneous  surface  does  not  permit  a  diminution  of  its  volume,  a  compression  (in 
consequence  of  the  loss  of  liquid  by  evaporation,)  it  is  obvious  that  an  equalization 
of  this  difference  in  pressure  can  only  take  place  from  within  outwards  ;  first  from 
within,  and  especially  from  those  parts  which  are  in  closest  contact  with  the 
atmosphere,  and  which  offer  the  least  resistance  to  the  action  of  the  external 
pressure. || 

Hence  it  follows,  that  the  fluids  of  the  body,  in  consequence  of  the  cutaneous 
and  pulmonary  transpiration,  acquire  a  motion  towards  the  skin  and  lungs,  which 
must  be  accelerated  by  the  circulation  of  the  blood. 

By  this  evaporation,  the  laws  of  the  mixture  of  dissimilar  liquids,  separated  by 
a  membrane,  must  be  essentially  modified.^  The  passage  of  the  food  dissolved 
in  the  digestive  canal,  and  of  the  lymph  into  the  blood  vessels,  the  expulsion  of 
the  nutritive  fluid  out  of  the  minuter  blood  vessels,  the  uniform  distribution  of 
these  fluids  in  the  body,  the  absorbent  power  of  the  membranes  and  skins,  which, 
under  the  actual  pressure  are  permeable  for  the  liquids  in  contact  with  them,  are 
under  the  influence  of  the  difference  in  the  atmospherical  pressure,  which  is 
caused  by  the  evaporation  of  the  fluids  of  the  skin  and  lungs. 

The  juices  and  fluids  of  the  body  distribute  themselves,  according  to  the  thick- 
ness of  the  walls  of  the  vessels,  and  their  permeability  for  these  fluids,  uniformly 
through  the  whole  body;  and  the  influence  which  a  residence  in  dry  or  in  moist 
air,  at  great  elevations  or  at  the  level  of  the  sea,  may  exert  on  the  health,  in  so  far 
as  the  evaporation  may  thus  be  accelerated  or  retarded,  requires  no  special  explana- 
tion ;  while  on  the  other  hand  the  suppression  of  the  cutaneous  transpiration  must 

*  Liquids  move  towards  the  membrane  from  which  evaporation  takes  place, 
•f  Influence  of  the  skin  and  cutaneous  transpiration  on  health. 

I  The  cutaneous  evaporation  has  an  important  share  in  causing  the  motion  of  the  animal  fluids, 
j  Evaporation  is  constantly  going  on  from  the  skin  and  lungs. 

II  This  evaporation  must  produce  unequal  pressure,  by  which  the  fluids  acquire  f   ^af;Uon  to- 
wards the  skin  and  lungs. 

fl  The  change  of  pressure  influences  the  mixture  of  the  fluids. 


36  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

be  followed  by  a  disturbance  of  this  motion,  in  consequence  of  which  the  normal 
process  is  changed  where  this  occurs. 

The  pressure,  which,  in  consequence  of  the  evaporation,  urges  the  fluids  within 
the  body  to  move  towards  tHe  skin,  is,  as  may  readily  be  understood,  equal  to  the 
difference  of  pressure  acting  on  the  surface  of  the  skin.* 

From  the  experiment,  Fig.  13,  it  is  plain,  that  when  one  of  the  two  surfaces  of 
bladder  at  the  ends  of  the  tube  Fig.  12,  is  exposed  to  atmospheric  evaporation, 
while  the  other  end  is  moistened  with  water,  brine,  or  oil,  these  liquids  are 
rapidly  absorbed  by  the  membrane,  that  is,  are  forced  in  by  the  external  atmospheric 
pressure,  and  it  is  not  less  obvious,  that  the  same  thing  takes  place  with  the  liquid 
with  which  one  of  the  two  evaporating  surfaces  has  been  moistened  in  the  middle 
only ;  while  the  evaporation  continues  around  the  moistened  spot. 

If,  therefore,  we  moisten  with  a  liquid  the  surface  of  the  evaporating  skin  at  any 
point,  the  liquid  is  forced  inwards  by  the  external  pressure.! 

Let  us  suppose  any  part  of  the  skin  to  be  rubbed  with  fat,  the  transpiration 
ceases  at  that  part.J  If  now  the  skin  around  the  part  is  in  its  normal  activity,  if, 
therefore,  in  the  surrounding  parts  liquid  is  constantly  passing  off  by  evaporation, 
the  fat  must  be  urged,  by  the  unequal  pressure  thus  arising,  towards  these  parts,  or 
it  is  absorbed,  just  as  water,  in  the  apparatus,  Fig.  12;  is  absorbed,  when  in  con- 
sequence of  evaporation  a  difference  between  the  internal  and  external  pressure 
has  arisen.  If  the  whole  skin  were  covered  with  fat,  the  absorption  would  be 
effected  by  the  pulmonary  evaporation. 

The  blistering  of  the  skin,  and  the  sun-burning,  to  which  men  are  exposed  at 
great  elevations,  arise  from  the  extraordinary  dryness  of  the  air,  the  increased 
evaporation,  and  the  pressure  by  which  the  fluids  filling  the  vessels  are  forced 
towards  the  surface. 

Several  causes  contribute  jointly  to  the  appearance  of  the  sweat,  to  the  efflux  of 
fluid,  from  the  pores  of  the  skin.  One  of  these  obviously  depends  on  the  velocity, 
which  the  fluid  set  in  motion  by  evaporation  or  by  a  mechanical  cause,  acquires 
from  the  accelerated  motion  of  the  blood.  In  consequence  of  this  velocity,  the 
fluid  moves  out  beyond  the  limits  of  the  absorbing  membrane  or  skin. 

The  changes  of  the  vital  process,  caused  by  the  unequal  distribution  of  fluid  in 
the  body  in  consequence  of  evaporation,  are  best  seen  in  animals  which  live  in 
water,  in  whom,  therefore,  the  above  explained  cause  of  motion  in  the  normal 
state  does  not  act.  When  a  fish  is  held  immersed  in  water,  so  that  the  head  is 
out  of  the  water,  while  the  rest  of  the  body  is  covered,  it  dies  in  a  few  minutes. § 
It  dies  exactly  in  the  same  way  when  head  and  gills  are  held  in  the  water,  and 
the  body  in  air  (MILNE  EDWARDS  ;)  in  both  cases,  without  loss  of  weight.  This 
fact  shows  that  even  if  the  weight  of  the  animal  be  kept  unaltered  by  the  absorp- 
tion of  water  through  the  body  kept  in  that  medium,  yet  the  distribution  of  the 
fluids  in  the  body  does  not  take  place  in  the  proportion  necessary  for  the  preser- 
vation of  their  vital  functions.  The  fish  dies. 

It  is  hardly  necessary  to  remind  the  reader,  that  the  experiments  described  in 
the  foregoing  pages,  in  so  far  as  they  permit  us  to  draw  conclusions  as  to  the 
cause  of  the  motion  r»f  the  juices  of  the  animal  body,  agree  in  all  respects  with 
the  observations  made  on  plants  by  STEPHEN  HALES  more  than  120  years  since.  || 

The  experiments  of  HALKS  on  the  mechanism  of  the  motion  of  the  sap,  may 
stand  as  a  pattern  to  all  times  of  an  excellent  method.  That  they  remain,  to  this 
moment,  unsurpassed  in  the  domain  of  vegetable  physiology,  may  be,  perhaps 
explained  by  the  fact  that  they  date  from  the  age  of  NEWTON.  They  ought  to  be 
familiar  to  every  vegetable  physiologis* 

In  the  beginning  of  his  work,  HALES  describes  the  experiments  which  he  made 


«  The  force  urging  the  fluids  towards  the  skin  is  equal  to  the  difference  of  pressure  acting  on 
the  skin. 

t  Liquids  placed  on  the  skin  are  absorbed  by  the  evaporation  of  other  parts, 
j  Effect  of  rubbing  fat  on  a  part  of  the  skin  or  on  the  whole  of  it. 
$  Fishes  die  in  tlr,  because  the  distribution  of  the  fluids  is  prevented. 
I  S.ipericannts  otf  HALES  on  the  motion  of  the  sap  in  plants. 


EXPERIMENTS   ON  THE    MOTION  OF  THE  SAP  OF  PLANTS.  37 

on  the  motion  of  the  sap  in  plants  in  consequence  of  their  evaporation  in  branches 
covered  with  foliage,  in  cut  plants  as  well  as  in  those  still  provided  with  roots. 

He  shows  by  the  following  experiment  the  influence  of  the  mechanical  pressure 
of  a  column  of  water,  with  and  without  the  help  of  evaporation. 

To  a  branch  of  an  apple  tree  bearing  its  twigs  and  leaves,  HALES  fastened,  air- 
tight, a  tube  seven  feet  long.  He  kept  the  branch  with  its  twigs  and  leaves 
immersed  in  a  large  vessel  of  water,  and  filled  the  tube  with  water.  By  the  pres- 
sure of  the  column  of  water,  water  was  forced  into  the  branch,  and  in  two  days 
the  water  in  the  tube  had  sunk  14|  inches. 

On  the  third  day,  he  took  the  branch  out  of  the  water,  and  exposed  it  to  free 
evaporation  in  the  air.  The  water  in  the  tube  fell,  in  twelve  hours,  27  inches. 

To  compare  the  force  with  which  water  is  driven  through  the  vessels  of  the 
wood,  by  pressure  alone,  with  that  produced  by  pressure  and  evaporation,  he  joined 
an  apple  branch,  6  feet  long,  with  leaves,  and  exposed  to  the  air,  with  a  tube  9 
feet  long,  which  was  filled  with  water. 

-  From  the  pressure  caused  by  the  column  of  water,  and  by  the  evaporation  going 
on  at  the  surface  of  the  twigs  and  leaves,  the  water  fell  (Xlth  experiment,)  in  one 
hour,  36  inches.  He  now  cut  off  the  branch  13  inches  below  the  tube,  and  placed 
the  portion  cut  off  (with  the  twigs  and  leaves)  vertically  in  a  vessel  of  water. 
This  last  absorbed,  in  30  hours,  18  ounces  of  water,  while  the  portion  of  wood 
remaining  in  connection  with  the  tube,  which  was  13  inches  long,  only  allowed  6 
ounces  of  water  to  pass,  and  that  under  the  pressure  of  a  column  of  7  feet  of 
water. 

HALES  shows  in  three  other  experiments,  that  the  capillary  vessels  of  a  plant, 
alone,  and  in  connection  with  the  uninjured  roots,  are  easily  filled  with  water  by 
capillary  attraction,  without,  however,  possessing  the  power  of  causing  the  sap  to 
flow  out  and  to  rise  in  a  tube  attached.*  The  motion  of  the  sap,  concludes  HALES, 
belongs  to  the  evaporating  surface  alone  ;  he  proves  that  it  goes  on  in  an  unequal 
degree  from  the  stem,  the  twigs,  the  flowers,  and  fruit,  and  that  the  effect  of  the 
evaporation  stands  in  a  fixed  ratio  to  the  temperature  and  hygrometic  state  of  the 
air.  If  the  air  were  moist,  but  little  were  absorbed ;  the  absorption  was  hardly 
perceptible  on  rainy  days. 

He  opens  the  second  chapter  of  his  Statistics  with  the  following  introduction :—— 

"  Having  in  the  first  chapter  seen  many  proofs  of  the  great  quantities  of  liquor 
imbibed  and  perspired  by  vegetables,  I  propose  in  this,  to  inquire  by  what  force 
they  do  imbibe  moisture.  Though  vegetables  (which  are  inanimate)  have  not  an 
engine,  which  by  its  alternate  dilations  and  contractions,  does  in  animals,  forcibly 
drive  the  blood  through  the  arteri'es  and  veins;  yet  has  nature  wonderfully  contrived 
other  means,  most  powerfully  to  raise  and  keep  in  motion  the  sap. 

In  his  experiment  XXL,  he  exposed  one  of  the  chief  roots  of  a  pear  tree  in  full 
growth  at  a  depth  of  2£  feet,  cut  off  the  point  of  it,  and  connected  the  part  of  the 
root  left  in  connection  with  the  stem  with  a  tube  which  he  filled  with  water  and 
closed  with  mercury. 

In  consequence  of  the  evaporation  from  the  surface  of  the  tree,  the  root  absorbed 
the  water  in  the  tube  with  such  a  force,  that  in  six  minutes  the  mercury  rose  to  8 
inches  in  the  tube.  This  corresponds  to  a  column  of  water  9  feet  high. 

This  force  is  nearly  equal  to  that  with  which  the  blood  moves  in  the  great 
femoral  artery  of  the  horse.  HALES,  in  his  experiment  XXXIV.,  found  the  force  of 
the  blood  in  various  animals;  "By  tying  those  several  animals  down  alive  upon  their 
backs,  and  then  laying  open  the  great  left  crural  artery,  where  it  first  enters  the 
thigh,  I  fixed  to  it  (by  means  of  two  brass  pipes  which  run  one  into  the  other)  a 
glass  tube  of  above  10  feet  long,  and  gth  of  an  inch  in  diameter  in  bore.  In  which 
tube  the  blood  of  one  horse  rose  8  feet  3  inches,  and  the  blood  of  another  horse  8 
feet  9  inches.  The  blood  of  a  little  dog  65  high." 

HALES  showed  by  special  experiments,  that  the  absorbent  force  which  he  pointed 
out  in  the  root  is  found  also  in  the  stem,  in  each  separate  twig,  each  leaf,  and  every 
part  of  the  surface ;  and  that  the  motion  of  the  sap  continues  from  the  root  towards 

*  The  motion  of  the  sap  is  caused  by  the  evaporating  surfece. 


38  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

the  twigs  and  leaves,  even  when  the  stem  has  been  entirely  stripped  of  bark, 
inner  and  outer.  This  force  acts  not  only  from  the  roots  in  the  direction  of  the 
summit  but  also  from  the  summit  in  the  direction  of  the  root. 

From  his  experiment  he  deduces  the  presence  of  a  powerful  attractive  force  resi- 
ding in  every  part  of  the  plant. 

We  now  know,  that  this  attractive  force,  as  such,  did  not  cause  the  rise  of  the 
mercury  or  water  in  his  tubes,  and  it  appears  clearly  from  his  experiments,  that 
the  absorbent  power  of  plants.,  of  each  leaf,  of  each  fibre  of  the  root,  is  sustained 
by  a  powerful  external  force  which  is  nothing  else  than  the  pressure  of  the  atmos- 
phere.* 

By  the  evaporation  of  water  at  the  surface  of  plants,  a  vacuum  arises  within 
them,  in  consequence  of  which  water  and  matters  soluble  in  water  are  driven 
inwards  and  raised  from  without  with  facility,  and  this  external  pressure,  along  with 
capillary  attraction,  is  the  chief  cause  of  the  motion  and  distribution  of  the  juices.t 

With  respect  to  the  absorbent  power  of  the  plant  for  gases,  under  a  certain  exter- 
nal pressure,  his  experiments  offer  the  most  beautiful  evidence.;}:  HALES  says,  in 
his  experiment  XXII.,  "  This  height  of  the  mercury  did  in  some  measure  show 
the  force  with  wfhich  the  sap  was  imbibed,  though  not  near  the  whole  force ;  for 
while  the  water  was  imbibing,  the  transverse  cut  of  the  branch  was  covered  with 
innumerable  little  hemispheres  of  air,  and  many  air-bubbles  issued  out  of  the  sap- 
vessels,  which  air  did,  in  part,  fill  the  tube  e  r,  as  the  water  was  drawn  out  of  it ; 
so  that  the  height  of  the  mercury  could  only  be  proportionable  to  the  excess  of  the 
quantity  of  the  water  drawn  off,  above  the  quantity  of  air  which  issued  out  of  the 
wood.  And  if  the  quantity  of  air  which  issued  from  the  wood  into  the  tube,  had 
been  equal  to  the  quantity  of  water  imbibed,  then  the  mercury  would  not  rise  at  all ; 
because  there  would  be  no  room  for  it  in  the  tube.  But  if  9  parts  of  12  in  the 
water  be  imbibed  by  the  branch,  and  in  the  mean  time,  but  three  such  parts  of  air 
issue  into  the  tube,  then  the  mercury  must  needs  rise  near  6  inches,  and  so  pro- 
portionably  in  different  cases." 

When,  in  his  experiments,  the  root,  the  stem,  or  a  twig  had  been  injured  at  any 
part,  by  the  cutting  off  of  buds,  root-fibres,  or  small  twigs,  the  absorbent  power 
of  the  remainder  was  diminished  in  a  very  obvious  degree  (because,  from  these 
places,  by  the  entrance  of  air  the  difference  of  air  was  more  easily  equalized  ;)§  the 
absorbent  power  was  greatest  on  freshly-cut  surfaces,  on  which,  however,  it  gra- 
dually decreased,  till,  after  several  days,  it  was  not  greater  in  these  places  than  in 
the  uninjured  surface  of  the  plant. 

The  evaporation,  further,  argues  HALES,  is  the  powerful  cause  which  provides 
food  for  the  plant  and  its  vicinity.  Disease  and  death  of  the  plant  follow,  when 
the  proportion  between  evaporation  and  supply  is  interrupted  or  destroyed  in  any 
way.  || 

When,  in  hot  summers,  the  earth  cannot  supply,  through  the  roots,  the  moisture 
which  during  the  day  has  evaporated  through  the  leaves  and  surface  of  the  tree,  when 
the  tree,  or  a  twig  of  it,  dries  up,  the  motion  of  the  sap  is  arrested  at  these  points. 
When  once  dried,  capillary  action  alone  cannot  restore  the  original  activity ;  the 
evaporation  is  the  chief  condition  of  the  life  of  plants ;  by  its  means  a  permanent 
motion,  a  continually  repeated  change  in  the  quality  of  the.  juice  (sap)  is  effected. 

"  By  comparing,"  says  HALES,  *'  the  surface  of  the  roots  of  plants,  with  the 
surface  of  the  same  plant  above  ground,  we  see  the  necessity  of  cutting  off  many 
branches  from  a  transplanted  tree :  for  if  256  square  inches  of  root  in  surface  was 
necessary  to  maintain  this  cabbage  in  a  healthy  natural  state;  suppose  upon  dig- 
ging it  up,  in  order  to  transplant,  half  the  roots  be  cut  off  (which  is  the  case  of 
most  young  transplanted  trees,)  then  it  is  plain  that  but  half  the  usual  nourishment 
can  be  carried  up,  through  the  roots,  on  that  account ;  and  a  very  much  less  pro- 


*  The  pressure  rf  the  atmosphere  is  the  active  force. 

t  A  partial  vacuum  is  caused  within  plants  by  evaporation. 

j  The  surface  of  plants  absorbs  gases. 

$  The  absorbent  power  diminished  by  injury  to  the  plant. 

||  Evaporation  provides  food  for  the  plant. 


OBSERVATIONS  OF  HALES  ON  THE  BLIGHT  IN  HOPS.  39 

portion,  on  account  of  the  small  hemisphere  of  eurth  the  new-planted,  shortened 
roots  occupy ;  and  on  account  of  the  loose  position  of  the  new-turned  earth,  which 
touches  the  roots  at  first  but  in  few  points." 

HALES  proves  the  influence  of  suppressed  evaporation  by  the  following  observa- 
tions on  hop-vines. 

"  Now  there  being  1,000  hills  in  an  acre  of  hop-ground,  and  each  hill  having 
three  poles,  and  each  pole  three  vines,  the  number  of  vines  will  be  9,000 ;  each 
of  which  imbibing  four  ounces,  the  sum  of  all  the  ounces,  imbibed  in  an  acre  in  a 
twelve  hours'  day,  will  be  36,000  ounces  =  15,750,000  grains  =  62,007  cubic 
inches,  or  220  gallons  ;  which  divided  by  6,272,640,  the  number  of  square  inches 
in  an  acre,  it  will  be  found,  that  the  quantity  of  liquor  perspired  by  all  the  hop- 
vines,  will  be  equal  to  an  area  of  liquor,  as  broad  as  an  acre,  and  yJT  part  of  an 
inch  deep,  besides  what  evaporated  from  the  earth.  And  this  quantity  of  moisture 
in  a  kindly  state  of  the  air  is  daily  carried  off  in  a  sufficient  quantity  to  keep  the 
hops  in  a  healthy  state ;  but  in  a  rainy  moist  state  of  air,  without  a  due  mixture 
of  dry  weather,  too  much  moisture  hovers  about  the  hops,  so  as  to  hinder  in  a 
good  measure  the  kindly  perspiration  of  the  leaves,  whereby  the  stagnating  sap 
corrupts,  and  breeds  mouldy  fen,  whicb  often  spoils  vast  quantities  of  flourishing 
hop-grounds." 

"  This  was  the  case  in  the  year  1723,  when  ten  or  fourteen  days'  almost  con- 
tinual rains  fell,  about  the  latter  half  of  July,  after  four  months'  dry  weather ; 
upon  which  the  most  flourishing  and  promising  hops  were  all  infected  with  mould 
or  fen,  in  their  leaves  and  fruit,  whilst  the  then  poor  and  unpromising  hops  escaped, 
and  produced  plenty  ;  because  they,  being  small,  did  not  perspire  so  great  a  quan- 
tity as  the  others  ;  nor  did  they  confine  the  perspired  vapor,  so  much  as  the  large 
thriving  vines  did,  in  their  shady  thickets.  This  rain  on  the  then  warm  earth  made 
the  grass  shoot  cut  as  fast  as  if  it  were  in  a  hot-bed  ;  and  the  apples  grew  so  preci- 
pitately, that  they  were  of  a  very  fleshy  constitution,  so  as  to  rot  more  remarkably 
than  had  ever  been  remembered."* 

44  The  planters  observe,  that  when  a  mould  or  fen  has  once  seized  any  part  of 
the  ground,  it  soon  runs  over  the  whole  ;  and  that  the  grass,  and  other  herbs  under 
the  hops,  are  infected  with  it." 

"  Probably  because  the  small  seeds  of  this  quick-growing  mould,  which  soon 
come  to  maturity,  are  blown  over  the  whole  ground.  Which  spreading  of  the 
seed  may  be  the  reason  why  some  grounds  are  infected  with  fen  for  several  years 
successively." 

44 1  have  in  July  (the  season  for  fire-blasts,  as  the  planters  call  them)  seen," 
says  HALES,  "  the  vines  in  the  middle  of  a  hop-ground  all  scorched  up,  almost 
from  one  end  of  a  large  ground  to  the  other,  when  a  hot  gleam  of  sunshine  has 
come  immediately  after  a  shower  of  rain ;  at  which  time  the  vapors  are  often  seen 
with  the  naked  eye,  but  especially  with  reflecting  telescopes,  to  ascend  so  plenti- 
fully, as  to  make  a  clear  and  distinct  object  become  immediately  very  dim  and 
tremulous.  Nor  was  there  any  dry  gravelly  vein  in  the  ground,  along  the  course 
of  this  scorch.  It  was,  therefore,  probably  owing  to  the  much  greater  quantity  of 
scorching  vapors  in  the  middle  thanoutsides  of  the  ground,  and  that  being  a  denser 
medium,  it  was  much  hatter  than  a  more  rare  medium." 

44  This  is  an  effect  which  the  gardeners  about  London  have  too  often  found  to 
their  cost,  when  they  have  incautiously  put  bell-glasses  over  their  cauliflowers 
early  in  a  frosty  morning,  before  the  dew  was  evaporated  off  them ;  which  dew 
being  raised  by  the  sun's  warmth,  and  confined  within  the  glass,  did  there  form  a 
dense,  transparent,  scalding  vapor,  which  burnt  and  killed  the  plants." 

When  these  observations  are  translated  into  our  present  language,  we  perceive 
with  what  acuteness  and  accuracy  HALES  recognized  the  influence  of  evaporation 
on  the  life  of  plants. 

According  to  him  the  development  and  growth  of  the  plant  depends  on  the 
supply  of  nourishment  and  moisture  from  the  soil,  which  is  determined  by  a  certain 

*  Observations  of  Hales  on  the  slight  in  hops  and  other  plants. 


40  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

temperature  and  dryness  of  the  atmosphere.  The  absorbent  power  of  plants — the 
motion  of  their  sap,  depends  on  evaporation ;  the  amount  of  food  necessary  for 
their  nutrition,  which  is  absorbed,  is  proportional  to  the  amount  of  moisture  given 
out  (evaporated)  in  a  given  time.  When  the  plant  has  taken  up  a  maximum  of 
moisture,  and  tha  evaporation  is  suppressed  by  a  low  temperature  or  by  continued 
wet  weather,  the  supply  of  food,  the  nutrition  of  the  plant,  ceases;  the  juices 
stagnate,  and  are  altered  ;  they  now  pass  into  a  state  in  which  they  become  a 
fertile  soil  for  microscopic  plants.  When  rain  falls  after  hot  weather,  and  is  fol- 
lowed by  great  heat  without  wind,  so  that  every  part  of  the  plant  is  surrounded 
by  an  atmosphere  saturated  with  moisture,  the  cooling  due  to  further  evaporation 
ceases,  and  the  plants  are  destroyed  by  fire-blast  or  schorching  (Sonnenbrand, 
German,  literally,  sun-burn  or  sun-blight.) 

After  the  experience  and  observations  of  so  long  a  period  in  reference  to  the 
influence  of  evaporation  on  the  condition  of  plants,  I  hardly  think  that  any  un- 
prejudiced observer  can  entertain  the  smallest  doubt  concerning  the  cause  of  the 
great  mischief  which  has  befallen  agriculture  during  the  last  few  years.*  If  HALES^ 
that  unequalled  observer  and  inquirer,  had  known  the  potato  disease,  I  hardly 
"believe  that  he  would  have  ascribed  it  to  an  internal  cause  belonging  to  the  plant, 
any  more  than  he  thought  of  ascribing  the  blight  of  the  hop  plants,  formerly  men- 
tioned, to  a  special  hop  di-sease,  or  the  rotting  of  the  apples  to  an  apple  disease. 
Even  PARMENTIER,  to  whom  France  is  indebted  for  the  introduction  of  the  potato, 
knew  this  disease,  and  has  very  accurately  described  it.t  The  term  "  potato-rot  " 
has  been  known  to  the  oldest  peasants  and  agriculturists  since  their  youth  ;  it  has, 
doubtless,  only  acquired  of  late  years  the  frightful  significance,  which  seems  to 
threaten  the  well  being  of  nations,  since  the  causes,  which  formerly  brought  it 
locally  into  existence,  have  spread  over  whole  districts  and  countries.  The  writings 
of  HALES  bring  to  our  century  from  a  preceding  one  the  consoling  certainty  (and 
this  is  especially  important,)  that  the  cause  of  this  decay  is  not  to  be  looked  for  in 
a  degeneration  of  the  plant,  but  depends  on  the  combination  of  certain  conditions 
accidentally  coincident ;  and  that  these,  when  they  are  well  ascertained  and  kept 
in  view,  enable  the  agriculturist,  if  not  to  annihilate,  at  least  to  diminish,  their  hurt- 
ful influence.! 

The  potato  plant  obviously  belongs  to  the  same  class  of  plants  as  the  hop  plant, 
namely,  to  that  class  which  is  most  seriously  injured  by  the  stagnation  of  their 
juices  in  consequence  of  suppressed  transpiration. §  According  to  KNIGHT,  the 
tubers  are  not  formed  by  swelling  of  the  proper  roots,  but  by  the  development  of  a 
kind  of  underground  stalks  or  runners.  He  found  that  when  the  tubers  under 
ground  were  suppressed,  tubers  were  formed  on  the  stalks  above  ground ;  and  it  is 
conceivable  that  every  external  cause  which  exerts  a  hurtful  influence  on  the 
healthy  condition  of  the  leaves  and  stalks,  must  act  in  like  manner  on  the  tubers. 
In  the  districts  which  were  most  severely  visited  by  the  so-called  potato  disease  in 
1846,  damp,  cold,  rainy  weather  followed  a  series  of  very  hot  days ;  and  in  1847, 
cold  and  rain  came  on,  after  continued  drought,  in  the  beginning  of  September, 
exactly  at  the  period  of  the  most  luxuriant  growth  of  the  potatoes. || 

In  most  places,  no  trace  of  disease  was  observed  in  the  early  potatoes  before  the 
middle  of  August ;  and  even  after  that  period  low-lying,  cold  and  wet  fields,  were 
chiefly  attacked  by  it.  In  many  plants,  in  the  same  field,  in  which  the  seed  pota- 
toes had  been  destroyed  by  putrefaction  and  decay,  the  tubers  appeared  quite  healthy, 
while  in  others  it  was  easy  to  see  that  these  tubers  alone,  which  lay  next  to  the 
old  potatoes,  were  infected  and  attacked  by  the  disease,  and  that  on  the  side  next 
to  the  old  tubers. ^f  i 

In  1846  all  the  potato  plants  in  my  garden  died  completely  off  towards  the  end 
of  August,  before  a  single  tuber  had  been  formed  ;  and  in  1847,  in  the  same  field, 

*  The  potato  blight  has  probably  a  similar  origin. 

t  The  potato  blight  has  been  long  known. 

t  It  is  not  due  to  a  degeneration  of  the  plant,  but  to  a  combination  of  external  causes. 

$  The  potato  plant  is  one  of  those  which  suffers  most  from  suppressed  evaporation. 

H  Character  of  the  weather  in  184G  and  1847,  when  the  potato  blight  prevailed. 

if  In  most  places  the  early  potatoes  escaped  till  after  the  middle  of  August. 


EFFECT  OF  COLD  ON  PLANTS.  41 

the  tubers  of  all  those  plants  which  stood  under  trees,  and  in  protected  spots,  were 
quite  rotten,  while  no  trace  of  disease  appeared  in  spots  which  were  more  elevated 
and  more  fully  exposed  to  the  current  of  air.  The  cause  of  the  disease  is  the  same 
which,  in  spring  and  autumn,  excites  influenza ;  that  is,  the  disease  is  the  effect 
of  the  temperature  and  hygrometric  state  of  the  atmosphere,  by  which,  in  conse- 
quence of  the  disturbance  of  the  normal  transpiration,  a  check  is  suddenly,  or  for 
a  considerable  time,  given  to  the  motion  of  the  fluids,  which  is  one  chief  condition 
of  life,  and  which  thus  becomes  insufficient  for  the  purposes  of  health,  or  even 
hurtful  to  the  individual.* 

The  whole  existence  of  a  plant,  the  ' esistance  which  it  opposes  to  the  action 
of  the  atmospheric  oxygen,  is  most  closely  connected  with  the  continued  support 
of  its  vital  functions.  The  mere  alternation  of  day  and  night  makes,  in  this 
respect,  a  great  difference.  The  sinking  of  the  external  temperature  by  a  few 
degrees,  causes  the  leaves  to  fall  in  autumn ;  and  a  cold  night  is  followed  by  the 
death  of  many  annual  plants. 

If  we  reflect  that  a  plant,  in  order  to  protect  itself  from  external  causes  of 
disturbance,  or  to  seek  the  food  which  it  requires,  cannot  change  its  place  ;  that  its 
normal  vital  functions  depend  on  the  simultaneous  and  combined  action  of  water, 
of  the  soil,  of  the  external  temperature,  and  of  the  hygrometric  state  of  the 
atmosphere ;  that  is,  on  four  external  circumstances  ;  it  is  easy  to  comprehend  the 
disturbance  of  functions  which  must  occur  in  the  organism  in  consequence  of  any 
change  in  the  mutual  relations  of  so  many  combined  agencies.f  The  state  of  a 
plant  is  a  sure  indication  of  equilibrium  or  misproportion  in  the  external  conditions 
of  its  life  ;  and  the  dexterity  of  the  accomplished  gardener  consists  exactly  in  this* 
that  he  knows  and  can  establish  the  just  proportion  of-  these  conditions  for  each 
species  of  vegetable.  Only  one  of  these  numerous  conditions!  is  in  the  power  of 
the  agriculturist,  and  that  is,  the  production  of  the  quality  of  the  soil  appropriate 
for  the  crop,  including  the  necessary  modification  of  its  composition,  by  the 
mechanical  working  of  the  soil ;  by  the  irrigation  or  draining  of  the  fields ;  and 
lastly,  by  the  employment  of  manure.  When  one  of  the  constituents 'of  the  soil, 
which,  under  the  given  circumstances,  is  necessary  for  the  support  of  the  vital  func- 
tions; is  absent,  the  external  injurious  influence  is  strengthened  by  this  deficiency. 
Had  this  constituent  been  present,  the  plant  would  have  been  enabled  to  oppose  to 
the  external  hurtful  influences  a  continued  resistance.  One  day  may  be  decisive 
as  to  the  life  or  death  of  a  plant.J  An  accurate  knowledge  of  the  influence  exerted 
by  the  various  constituents  of  the  soil  on  the  diseased  condition,  must  enable  the 
agriculturist  to  protect  and  preserve  many  of  his  fields  for  a  long  time  from  this 
destruction  ;  but  it  is  obvious  that  a  universal  remedy  against  this  evil  does  not  exist. 

When  the  vessels  of  the  plant  are  filled  to  overflowing  with  water,  and  the  motion 
of  the  sap  is  suppressed,  the  nutrition,  in  most  plants,  is  arrested,  and  death  takes 
place.  Every  one  knows  the  effect  of  a  sudden  or  of  a  gradual  overfilling  of  certain 
parts  or  organs,  when  the  corresponding  evaporation  is  suppressed.  By  the  endos- 
motic  pressure  of  the  water  flowing  towards  those  cells,  which  contain  sugar, 
mucilage,  gum,  albumen,  and  soluble  matters  in  general,  the  juicy  fruits  and  seeds 
approaching  maturity  burst,  an-d  the  juice  of  grapes,  cherries,  plums,  &c.,  passes, 
on  contact  with  the  air,  into  a  state  of  progressive  change.  The  fungi  which  have 
been  observed  on  the  potato  plants  and  the  putrefaction  of  the  tubers,  are  not  the 
signs  of  a  disease,  but  the  consequences  of  the  death  of  the  plant.§ 

Among  the  most  important  of  the  experiments  made  by  Hales  we  must  reckon 
undoubtedly  those  on  the  rise  of  the  spring  sap  in  perennial  plants.  His  observa- 
tions have  been  entirely  confirmed  by  all  those  who  since  his  time  have  studied 
the  subject;  but,  in  my  opinion,  without  our  having  approached  one  step  nearer  to 
the  cause  of  the  phenomena. 

*  The  cause  of  potato  blight  is  the  same  as  that  of  influenza,  and  depends  on  the  temperature 
and  hygrometric  state  of  the  air. 

f  The  life  of  plants  is  dependent  chiefly  on  four  external  causes  :  only  one  of  which,  namely, 
the  quality  of  the  soil,  in  the  power  of  the  agriculturist. 

J  Effects  of  the  presence  or  absence  of  a  single  constituent  of  the  soil. 

j  Tlu  plant  dies,  and  fungi  and  putrefaction  follow. 

ft 


42  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

The  most  recent  experiments  on  this  subject  by  E.  BRUCKE,  leave  no  doubt  in 
regard  to  the  actual  state  of  our  knowledge. 

According  to  DUTROCHET,  it  is  the  extremities  of  the  radical  fibres,  called  by  DE 
CANDOLLE,  spongioles,  which  effect  the  rise  of  the  spring  sap;  and  he  believes 
(L'agent  immediat  du  mouvement  vital,  Paris,1826,)  that  the  force  with  which  the 
sap  is  driven  upwards,  acts  from  the  root.  DUTROCHET  cut  off  a  peice  of  a  vine 
stem,  two  metres  long;  and  he  saw  that  the  sap  flowed  steadily  from  the  shortened 
stem  in  connection  with  the  root.  When  he  had  again  cut  it  off  close  to  the  ground, 
he  observed  the  portion  in  the  ground  continued  to  pour  forth  sap  from  the  whole 
cut  surface.  He  pursued  the  experiment,  going  deeper  every  time,  and  he  always 
found  that  the  sap  flowed  from  the  part  left  in  the  ground,  till  at  last  he  came  to 
the  extreme  points  of  the  fibres,  in  which  he  then  located  the  origin  of  the  moving 
force. 

The  peculiar  activity  of  the  spongioles  must,  according  to  DUTROCHET,  be 
ascribed  to  all  the  causes,  taken  together,  which  determine  the  phenomena  of 
endosmosis. 

Now  that  we  are  better  acquainted  with  the  phenomena  of  what  is  called  endos- 
mosis, we  may  oppose  to  this  view  some  well  founded  doubts.  All  observers  agree, 
that  the  increase  in  volume  of  a  liquid,  separated  from  another  liquid  by  a  porous 
diaphragm,  is  determined  by  a  difference  in  the  qualities  of  the  two  liquids.  If 
their  composition  and  properties  be  the  same,  there  is  no  cause  sufficent  to  produce 
mixture  and  change  of  volume,  since  in  this  case,  the  attraction  of  both  for  the 
diaphragm,  and  for  each  other,  is  perfectly  equal. 

In  the  course  of  his  admirable  researches,  BRUCKE  determined  the  specific  gravity 
of  the  spring  sap  which  had  flowed  from  the  vine.*  He  found  it,  in  one  plant 
==  1-0008,  and  in  another,=  l-OOO^1) 

These  numbers  prove  irresistably,  that  in  the  specific  gravity  of  the  sap  of  the 
vine  is  in  no  way  different  from  that  of  ordinary  spring  water,  or  of  the  water 
which  has  filtered  through  garden  mould.  In  most  cases,  spring  water  contains 
even  more  dissolved  matter. 

The  spring  sap  of  the  vine,  which  had  the  sp.  g.  1-0008,  raised  a  column  of 
mercury  to  the  height  of  174  lines  (14-5  inches,)  and  therefore  exerted  a  pressure 
equal  to  that  of  a  column  of  water  195  inches  high.  It  is  quite  impossible  to 
account  for  this  pressure  by  the  difference  in  the  amount  of  dissolved  matter  in  the 
water  absorbed  by  the  roots,  and  the  sap  flowing  from  the  cut  surface.  In  the 
experiment  No,  IX.,  of  BRUCKE,  made  with  a  vine,  the  sap  of  which  had  the  sp.  g. 
1-0009  the  mercury  was  raised  at  7  A.  M.,  to  the  height  of  209  lines,  (nearly  17-5 
inches. 

No  one  can  doubt  that  what  is  called  endosmosis  has  some  share  in  the  rise  of 
the  sap  of  the  maple  and  birch  trees,  which  is  proportionally  rich  in  sugar,  and 
differs  materially  in  composition  from  spring  water,  as  well  as  on  the  flow  or  exu- 
dation of  gummy  or  saccharine  juices;  but  the  pressure  exerted  in  these  cases, 
cannot  be  compared  to  that  exerted  by  the  sap  of  the  vine,  where  the  causes 
included  under  the  word  endosmosis  cannot  act. 

It  is  evident,  that  the  cause  of  the  pressure  of  the  spring  sap  must  be  transient, 
called  into  action  by  external  causes,  and  limited  to  a  short  period.t  The  experi- 
ment of  DUTROCHET,  from  which  he  concludes  that  the  cause  of  the  rise  of  the  sap 
resides  in  the  extreme  points  of  the  roots,  may  be  thus  interpreted  : — "  The  cause 
of  the  efflux  and  pressure  of  the  sap  exists  in  all  parts  of  the  uninjured  plant,  down 
to  the  extreme  spongioles  of  the  root." 

The  present  season  does  not  admit  of  experiments  on  this  point ;  but  as  spring 
approaches,  it  may  be  proper  here  to  develope  more  clearly  the  grounds  of  the 
opinion,  that  the  cause  of  the  efflux  of  the  sap  of  the  vine  is  a  transient  one.  Per- 
haps some  one  may  thus  be  induced  to  decide  experimentally  all  the  questions  of 
this  remarkable  phenomenon. 

(l)  Poggendorf  s  Annalen  der  Physik,  Ixiii.  177. 

*  Observations  of  BRUCKE  on.the  specific  gravity  of  the  sap  of  vinos. 

t  The  cause  of  the  rise  of  the  sap  is  transient ;  and  depends  on  external  influences 


EXPERIMENTS  OF  HALES.  43 


HALES,  in  his  experiment  XXXIV.,  cut  off  a  vine  stem  7  feet  above  the 
ground,  and  attached  to  the  trunk  tubes  of  7  feet  long,  joined  together.  Below 
the  cut  there  were  no  branches.  This  was  done  on  the  30th  of  March,  at  3  P.M. 

As  the  stem  poured  out  no  sap  on  that  day,  he  poured  water  into  the  attached 
tube  to  the  height  of  two  feet. 

This  water  was  absorbed  by  the  stem,  so  that  about  8  P.M.,  the  water  had  fallen 
to  3  inches  in  the  tube. 

The  next  day,  |  past  6  A.  M.,  the  sap  stood  3  inches  higher  than  at  8  the 
evening  before.  From  this  time  the  sap  continued  to  rise,  till  it  reached  a  height 
of  21  feet.  It  would  perhaps,  says  HALES,  have  risen  higher,  had  the  joinings- 
of  the  tubes  been  more  water-tight. 

Whatever  opinion  we  may  entertain  as  to  the  cause  of  the  efflux  and  pressure 
of  the  sap,  it  is  impossible  to  suppose  that  the  mechanical  or  any  other  structure 
or  quality  of  the  radical  fibres,  the  spongioles,  or  the  inner  parts  of  the  vine  stem 
generally,  can  have  changed  so  much  between  the  evening  of  the  30th  and  the 
morning  of  the  31st,  as  to  give  rise  to  two  completely  opposite  influences. 

On  the  evening  of  the  30th  the  water  poured  into  the  tube  was  absorbed  ;  on 
the  31st  it  was  expelled  with  a  continually  increasing  force. 

In  his  experiment  XXXVII.,  HALES  fixed,  on  three  branches  of  a  horizontally 
trained  espalier  vine,  siphon  tubes,  filled  to  a  certain  point  with  mercury. 

The  three  branches  received  their  sap  from  the  common  stem,  that  stem  from 
the  root.  The  first  branch  was  7  feet  from  the  second,  the  second  22  feet  9 
inches  from  the  third.  The  first  and  third  branches  were  two  years  old,  the 
middle  one  was  older. 

From  the  4th  to  the  20th  of  April,  the  mercury  stood,  in  consequence  of  the 
pressure  of  the  sap,  higher  in  the  open  limb  of  the  tubes  than  in  the  other  which 
was  attached  to  the  branch. 

The  greatest  height  attained  by  the  mercury  was  from  21  to  26  inches. 

On  the  21st  of  April,  when  the  flowering  was  nearly  over,  the  sap  in  the  middle 
branch  went  backwards  ;  it  was  absorbed,  and  so  considerably,  that  the  mercury 
stood  4  inches  lower  in  the  open  limb  than  in  the  other.  After  a  rainy  night  on 
the  24th  of  April,  the  sap  again  rose  in  the  open  tube  4  inches. 

In  the  first  (lowest)  branch,  the  sap  went  back  on  the  29th  of  April,  9  days 
after  the  middle  one ;  the  third  (highest)  branch  only  began  to  absorb  the  sap  on 
the  3d  of  May,  thirteen  days  after  the  middle  one. 

We  see  from  this  experiment,  as  HALES  observes,  "  That  the  cause  which 
produces  the  flow  of  the  sap  does  not  proceed  from  the  root  alone,  but  that  it 
belongs  to  a  force  inherent  in  the  stem  and  branches.  For  the  middle  branch 
followed  more  rapidly  the  changes  of  temperature,  of  dryness  and  of  moisture, 
than  the  two  others,  and  absorbed  the  sap  nine  days  before  one,  and  thirteen  days 
before  the  other,  both  of  which,  during  this  time,  poured  out  sap  instead  of 
absorbing  it.  (The  cause  of  the  efflux  and  pressure  had,  in  the  older  branch,  dis- 
appeared, and  given  place  to  an  opposite  influence,  while  it  still  continued  active 
in  the  two  younger  branches.) 

"  The  middle  branch  was  3  feet  8  inches  higher  than  that  next  the  stem.  The 
height  of  the  mercury  in  the  three  tubes  was,  respectively,  14£,  12£,  and  13 
inches.  The  maximum  was  21,  26,  and  26  inches.  These  numbers  prove  that 
the  greater  length  of  the  middle  branch  had  no  perceptible  influence  on  the  height 
of  the  mercury,  as  compared  with  that  in  the  other  tube." 

In  his  experiment  XXXVIII.,  HALES  observes, — "  Moisture  and  warmth  made 
the  sap  most  vigorous.  If  the  beginning  or  middle  of  the  bleeding  season,  being 
very  kindly,  had  made  the  motion  of  the  sap  vigorous,  that  vigor  would  imme- 
diately be  greatly  abated  by  cold  easterly  winds.* 

"If  in  the  morning  while  the  sap  is  in  a  rising  state,  there  was  a  cold  wind  with 
a  mixture  of  sunshine  and  cloud ;  when  the  sun  was  clouded  the  sap  would 
immediately  visibly  subside,  at  the  rate  of  an  inch  in  a  minute  for  several  inches, 
if  the  sun  continued  so  long  clouded ;  but  as  soon  as  the  sunbeams  broke  out 


*  Effect  of  cold  and  of  shade  on  tte  rise  of  the  sap. 


44  MOTION  OF  THE  JUICES  OF  THE  ANIMAL  BODY. 

again,  the  sap  would  immediately  return  to  its  then  rising  state,  just  as  any  liquor 
in  a  thermometer  rises  and  falls  with  the  alternacies  of  heat  and  cold  ;  whence  it 
is  probable,  that  the  plentiful  rise  of  the  sap  in  the  vine  in  the  bleeding  season,  is 
effected  in  the  same  manner." 

If  we  consider,  that  the  sap  in  spring,  even  with  a  clouded  sky,  does  not  cease 
to  rise  and  flow,  for  this  even  goes  on  during  the  night,  we  cannot  explain  the  fall 
of  the  sap  from  the  moment  that  the  sun  was  covered  by  a  cloud  by  a  mere  change 
of  temperature  in  the  juice,  because  the  time  was  too  short  for  the  cooling  and 
contraction  by  cooling  (one  inch  in  a  minute.)*  Heat  determined  the  more  rapid 
rise,  and  cold  the  fall,  but  they  acted  on  a  cause  which  lay  higher  than  the  root, 
and  which  was  more  sensitive  to  heat  than  the  liquid  itself. 

HALES  says,  in  his  experiment  XXXVIII. — «« In  very  hot  weather  many  air 
bubbles  would  rise,  so  as  to  make  a  froth  an  inch  deep,  on  the  top  of  the  sap  in 
the  tube.t 

"  I  fixed  a  small  air  pump  to  the  top  of  a  long  tube,  which  had  twelve  feet  height 
of  sap  in  it ;  when  I  pumped,  great  plenty  of  bubbles  arose,  though  the  sap  did 
not  rise,  but  fell  a  little,  after  I  had  done  pumping." 

In  his  experiments  on  the  amount  of  air  absorbed  by  plants,  chapter  V.,  he 
observes,  "  in  the  experiments  on  vines,  the  very  great  quantity  of  air  which  was 
continually  ascending  from  the  vines,  through  the  sap  in  the  tubes ;  which  mani- 
festly shows  what  plenty  of  it  is  taken  in  by  vegetables,  and  is  perspired  off  with 
the  sap  through  the  leaves." 

When  we  take  these  facts  into  consideration,  the  opinion  appears  not  untenable, 
that  the  incomprehensible  force,  which  causes  the  sap  of  the  vine  to  flow  in  spring, 
may  be  simply  referred  to  a  disengagement  of  gas  which  takes  place  in  the 
capillary  vessels  (filled  with  liquid,  and  keeping  themselves  constantly  full,)  in 
consequence  of  a  kind  of  germination ;  and  it  is  possible  that  the  height  of  the 
column  of  mercury,  or  of  water,  is  only  a  measure  of  the  elasticity  of  the  dis- 
engaged gas.J 

Let  us  suppose  a  strong  glass  bottle,  in  the  mouth  of  which  a  long  tube,  open 
at  both  ends,  and  reaching  to  the  bottom,  is  cemented,  to  be  filled  with  a  liquid  in 
which,  from  any  cause,  a  gas  is  disengaged  (solution  of  sugar  mixed  with  yeast, 
for  example,)  it  is  evident  that  the  liquid  must  rise  in  the  tube  from  the  separation 
of  the  gas.  When  it  has  risen  to  32  feet,  the  gas  will  occupy  only  the  half,  and 
at  64  feet,  one  third  of  its  volume  under  the  usual  atmospheric  pressure.  In  this 
case,  the  height  of  the  liquid  in  the  tube  is  no  measure  of  a  special  power  residing 
in  the  walls  of  the  vessel ;  it  only  shows  the  tension  of  the  gas. 

If  the  walls  of  the  vessel  were  permeable  to  the  gas  under  a  certain  pressure,  no 
further  rise,  beyond  that  point,  could  occur. 

If,  in  the  apparatus,  Fig.  4,  we  push  the  tube  a  through  the  cork  down  to  the 
little  lead  drop ;  if  we  then  fill  the  tube  c  with  water  to  which  some  yeast  has 
been  added,  and  a  with  solution  of  sugar,  and  expose  the  whole  to  a  temperature 
of  from  68°  to  75°,  the  liquid  rises  in  6,  from  the  gas  disengaged  in  c,  very 
rapidly,  so  as  to  overflow.  If  c  be  filled  with  solution  of  sugar,  and  a  with  yeast, 
the  same  rise  occurs,  and  lasts  till  the  disengaged  gas  puts  an  end  to  the  contact 
between  the  membrane  and  the  liquid 

It  is  hardly  necessary  to  point  out,  that  the  idea  above  expressed  as  to  the 
cause  of  the  flow  and  pressure  of  the  spring  sap,  is  nothing  more  than  an  indication 
of  the  direction  in  which  experiments  must  be  made.  When  we  know  with 
accuracy  the  volume  of  the  liquid  which  flows  out  of  a  vine  at  the  time  of  flowering, 
and  the  quantity  of  gas  which  is  developed  at  the  same  time,  we  shall,  I  trust, 
find  ourselves  a  step  nearer  to  the  explanation  of  this  phenomenon.  According 
to  the  experiments  of  GEIGER  and  PROUST,  the  sap  of  the  vine  is  rich  in  carbonic 
acid ;  and  it  is  possible  that  the  gas  which  is  disengaged,  may  be  no  other  than 
carbonic  acid  gas. 

*  How  is  this  effect  to  be  accounted  for  ? 

t  Gas  is  given  off  with  the  sap. 

t  The  rise  of  the  sap  may,  therefore,  be  caused  by  th   evolution  of  gas. 


APPENDIX. 


ON  THE  NATURE  AND  PREVENTION   OF  THE  POTATO  DISEASE. 

AFTER  the  preceding  pages  were  in  print,  I  received  from  Baron  Liebig  3  copy 
of  the  Journal  of  the  Agricultural  Association  of  the  Grand  Duchy  of  Hesse, 
(Darmstadt,)  No*  7,  dated  15th  February,  1848,  containing  the  account  of  a 
method  proposed  by  Dr.  Klotzsch  (Keeper  of  the  Royal  Herbarium,  Berlin,  and 
a  distinguished  Botanist  and  Vegetable  Physiologist,)  for  preventing  the  ravages  of 
the  potato  disease.  The  proposal  of  Dr.  Klotzsch,  and  his  views  as  to  the  nature 
of  the  disease,  are  such  as  materially  to  strengthen  the  opinions  expressed  on  this 
subject  by  Baron  Liebig,  (see  pp.  87,  seq.)  As  a  knowledge  of  the  method 
suggested  by  Dr.  Klotzsch  is  likely  to  be  interesting  to  many  of  the  readers  of 
this  work,  I  have  thought  it  right  to  give  it  in  an  Appendix. 

WILLIAM  GREGORY. 


METHOD  PROPOSED  BY  DR.  KLOTZSCH,  FOR  THE  PROTECTION  OF  THE 
POTATO  PLANT  AGAINST  DISEASES 

The  potato,  which  is  an  annual  plant,  represents,  in  the  tubers  developed  from  the 
stem,  the  perennial  part  of  a  plant.  For  while  the  duration  of  its  development  is 
analogous  to  that  of  annuals,  its  functions  coincide  exactly  with  those  of  dicotyle- 
donous shrubs  and  trees. 

"  The  potato  plant  differs  from  all  those  plants  which  are  cultivated  for  economical 
purposes  in  Europe,  and  can  only  be  compared  to  those  orchideous  plants  which 
yield  salep,  and  which  are  not  yet  cultivated  among  us. 

"  The  tubers,  both  of  the  potato  and  of  the  salep  plants,  are  nutritious,  and  agree 
in  this,  that  in  the  cells  of  the  tubers,  grains  of  starch,  with  more  or  less  azotized 
mucilage,  are  collected,  while  the  cell  walls  possess  the  remarkable  property  of 
swelling  up  into  a  jelly,  and  thus  becoming  easily  digestible,  when  boiled  with 
water. 

"  But  while  the  tuber  of  salep  contains  only  one  bud,  or  germ,  the  potato  usually 
develops  several,  often  many,  germs. 

"  The  potato  plant,  like  all  annuals,  exerts  its  chief  efforts  in  developing  flowers 
and  fruit.  Like  all  annuals,  too,  it  has  the  power  of  shortening  this  period  of 
development,  when  the  power  of  the  roots  is  limited  ;  as  also  of  lengthening  it 
when  the  extent  and  power  of  the  roots  are  increased. 

We  observe  in  nature  that  plants  with  feebly  developed  roots  often  have  a  weak, 
sickly  aspect,  but  yet  come  to  maturity  in  flower  and  fruit  sooner  than  stronger 
individuals,  well  furnished  with  roots. 


(45) 


46  APPENDIX. 


"  In  perennial  plants  we  observe  a  second  effort,  which  is  directed  towards 
preparing  and  storing  up  nutritious  matter,  for  the  consumption  of  the  plant.  The 
preparation  of  this  nutriment  is  effected  by  the  physiological  action  of  the  leaves, 
under  the  influence  of  the  roots.  The  stronger  and  larger  the  former  are,  the 
more  is  this  preparation  of  food  delayed. 

"  The  nutritious  matters  are  stored  in  the  colored  stratum  of  the  bark  in  shrubs 
and  trees,  and  in  the  tubers  in  the  potato  and  salep  plants.  Not  only,  however, 
the  nutrient  matters,  but  also  the  cells,  owe  their  origin  to  the  physiological  action 
of  the  leaves. 

"  On  considering  these  things,  it  follows,  that  the  potato  plant  requires  more 
care  than  is  usually  devoted  to  it.  Hitherto  the  whole  cultivation  consisted  in 
clearing  off  weeds,  and  hoeing  up  the  earth  round  the  stems.  Both  of  these 
measures  are,  indeed,  necessary,  but  they  are  not  alone  sufficient ;  for  the  plant  is 
cultivated,  not  on  account  of  its  fruit,  but  for  the  sake  of  its  tubers,  and  our  treat- 
ment should  be  modified  accordingly. 

"  The  chief  points  to  be  attended  to,  with  a  view  to  the  attainment  of  this  object, 
namely,  the  increase  of  tubers,  are — 

1.  To  increase  the  power  in  the  roots,  and 

2.  To  check  the  transformation  which  occurs  in  the  leaf. 

"  We  obtain  both  ends  simultaneously,  if,  in  the  5th,  6th,  and  7th  week  after 
setting  the  tubers,  and  in  the  4th  and  5th  week  after  planting  out  germs  furnished 
with  roots,  or  at  a  time  when  the  plants  reach  the  height  of  6  to  9  inches  above 
the  soil,  we  pinch  off  the  extreme  points  of  the  branches  or  twigs  to  the  extent  of 
half  an  inch  downwards,*  and  repeat  this  on  every  branch  or  twig,  in  the  10th 
and  llth  week,  no  matter  at  what  time  of  day. 

"  The  consequences  of  this  check  to  the  development  of  the  stem  and  branches, 
is  a  stimulous  to  the  nutrient  matters  in  the  plant  in  the  direction  of  the  increase, 
both  of  roots  and  of  the  multiplication  of  the  branches  of  the  stem  above  ground, 
which  not  only  favors  the  power  of  the  root,  but  also  strengthens  the  leaves  and 
stalks  to  such  a  degree,  that  the  matters  prepared  by  the  physiological  action  of 
these  parts  are  increased  and  applied  to  the  formation  ox  tubers,  while  at  the  same 
time  the  direct  action  of  the  sun's  rays  on  the  soil  is  prevented  by  the  thick  foliage, 
and  thus  the  drying  up  of  the  soil  and  its  injurious  consequences  are  avoided. 

The  checking  of  the  transformation  in  the  leaf  is  equivalent  to  the  interruption 
of  the  natural  change  of  the  leaves  into  calyces,  corollas,  stamens,  and  pistfls,  which 
is  effected  at  the  expense  of  the  nutrient  matters  collected  in  the  plant ;  and  these, 
when  this  modification  of  the  leaves  is  arrested,  are  turned  to  account  in  the  forma- 
tion of  tubers. 

"  Led  by  these  views,  I  made,  in  1846,  experiments  on  single  potato  plants, 
carefully  marked  by  pinching  off  the  ends  of  the  branches.  They  were  so  readily 
distinguished  in  their  subsequent  growth  from  the  plants  beside  them,  by  more 
numerous  branches,  larger  and  darker  foliage,  that  in  truth  no  marking  was  neces- 
sary. 

"The  produce  from  these  plants  of  tubers  was  abundant,  and  the  tubers  were 
perfectly  healthy ;  while  the  plants  next  them  which  had  not  been  so  treated,  gave 
uniformly  less  produce,  at  the  same  time  the  tubers  were  rough  on  the  surface, 
and  in  many  instances  attacked  with  the  prevailing  disease.  This  experiment  was 
incomplete,  and  did  not  give  a  positive  result,  but  it  was  yet  encouraging  for  me. 

"  In  the  middle  of  April,  1847,  an  experiment  was  made  on  a  low-lying  field 
with  the  round  white  potatoes,  generally  cultivated  here,  a  variety  which  had  not 
suffered  much  from  the  disease  which  first  appeared  here  1845.  The  potatoes 
were  planted  in  the  usual  way  by  an  experienced  farm  servant. 

**  After  weeding  them  in  the  end  of  May,  I  renewed  my  experiment  by  pinching 
off  the  points  of  the  branches  of  every  second  row,  and  repeated  this  in  the  end  of 
June.  The  result  surpassed  all  expectations.  The  stocks  of  the  plants  not  treated 

*  Any  one  would  be  bitterly  disappointed,  who  on  the  principle,  that  "  there  cannot  be  too 
much  of  a  good  ( hing,"  should  take  off  more  than  is  here  recommended,  in  order  to  use  it  as 
fodder. 


APPENDIX.  47 


on  my  plan,  were  long,  straggling,  and  sparingly  furnished  with  leaves,  the  leaves 
themselves,  small  and  pale  green. 

"  In  the  next  field,  potatoes  of  the  same  variety  were  planted  on  the  same  day 
and  left  to  nature.  They  appeared  in  the  first  six  weeks  healthy,  even  strong,  but 
gradually  acquired  a  poor  aspect  as  the  time  of  flowering  and  fruit  approached,  and 
finally,  exhibited  precisely  the  same  appearance  as  the  rows  not  treated  by  pinching 
off  the  extremities  in  the  field  in  which  my  experiments  were  made. 

"  The  harvest  began  in  the  surrounding  fields  in  the  middle  of  August,  and  was 
very  middling.  The  tubers  were  throughout  smaller  than  usual,  very  scabby,  and 
within  these  fields,  to  a  small  extent,  attacked  by  the  wet  rot. 

"  In  the  end  of  August,  the  difference  between  the  rows  treated  by  me  and  those 
not  treated,  became  so  striking  that  it  astonished  all  the  work  people  in  the  neigh- 
borhood, who  were  never  tired  of  inquiring  the  cause.  The  stocks  of  the  rows 
left  to  themselves  were  all  now  partly  dried,  partly  dead.  On  the  contrary,  the 
rows  treated  as  above  were  luxuriant  and  in  full  vigour,  the  plants  bushy,  the  foliage 
thick,  the  leaves  large  and  green,  so  that  most  people  suppposed  they  had  been  later 
planted. 

"But  the  difference  in  the  tubers  was  also  very  decided.  The  tubers  of  the 
plants  in  the  rows  treated  on  my  plan  were  not,  indeed  larger,  but  vastly  more 
numerous,  and  they  were  neither  scabby  nor  affected  with  any  disease  whatever. 
A  few  had  pushed  (which  was  to  be  ascribed  to  a  late  rain,)  and  were  apparently 
incompletely  developed,  while  scab  and  wet  rot  attacked  more  and  more  the  tubers 
of  the  other  plants,  which  also  fell  off  on  the  slightest  handling. 

"  Although  I  am  far  from  believing  that  I  am  able  to  explain  the  nature  of  the 
potato  disease  which  has  visited  us  of  late  years,  yet  I  feel  certain  that  I  have  dis- 
covered a  means  of  strengthening  the  potato  plant  to  such  a  degreea  s  to  enable  it 
to  resist  the  influences  which  determine  such  diseases. 

«•  Should  any  one  be  deterred  from  continuing  the  cultivation  of  potatoes,  on 
account  of  the  manipulation  here  recommended,  which  may  be  performed  by 
women  and  even  by  children,  I  would  remind  him  that  the  same  field  planted  with 
potatoes  is  capable  of  supplying  food  to  twice  as  many  persons  as  when  employed 
to  growing  wheat." — From  the  Annals  of  Agriculture  in  Prussia,  edited  by  the 
College  of  Rural. Economy. 

DR.  KLOTZSCH  presented  to  the  King  of  Prussia  a  memorial  offering  to  give  to 
the  world  his  method  of  preventing  disease  in  potatoes,  provided  he  were  assured 
of  a  remuneration  of  2,000  dollars,  (about  ^300,)  if,  after  three  years  experience  it 
should  be  found  efficacious. 

The  King  handed  the  memorial  to  the  Minister  of  the  Interior,  who  requested 
.he  College  of  Rural  Economy  to  discuss  the  matter  with  Dr.  Klotzsch. 

The  president  of  the  college  undertook  the  arrangement,  and,  after  Dr.  Klotzsch 
had  explained  to  him  privately  his  method,  reported  most  favorably  of  it  to  the 
College,  which  unanimously  recommended  that  the  very  moderate  remuneration 
asked  for  by  Dr.  Klotzsch  should  be  secured  to  him  on  the  following  conditions, 
which  were  accepted  by  him. 

1.  That  the  College  of  Rural  Economy  should  be  the  judges  of  the  efficacy 
of  the  proposed  method. 

2.  That  their  decision  should  be  given,  at  latest,  within  three  years,  provided 
the  potato  disease  against  which  the  plants  are  to  be  protected,  should 
appear  during  that  period. 

The  Minister  of  the  Interior  approved  of  the  recommendation*,  and  authorized 
the  College  to  conclude  an  agreement  with  Dr.  Klotzsch. 

The  agreement  has  been  concluded,  and  now  the  method  is  published  that  it 
may  be  tried  and  tested  as  widely  as  possible  by  comparative  experiments,  similar 
to  those  made  by  Dr.  Klotzsch  himself.  The  cost  of  it  is  stated  not  to  exceed  1*. 
6d.  per  acre  in  Germany. 

It  is  very  desirable  that  this  method  should  be  tried  in  the  British  Islands,  and 
as  the  season  for  trying  it  now  approaches,  I  have  here  given  Dr.  Klotzch's 
account  entire.  WILLIAM  GREGORY. 

THE  END. 


CHEMISTRY  AND  PHYSICS 


IN   RELATION   TO 


PHYSIOLOGY  AND  PATHOLOGY. 


,  BY  KM  Jims  LIEBIC,  ll.D,,  P.B.D.,  FAS,.  Mill 

AUTHOR  OF  "AGRICULTURAL   CHEMISTRY,"  "ANIMAL   CHEMISTRY," 
"MOTION  OF  JUICES  IN  ANIMAL  BODY,  AND  CURE  OF  THE 
POTATO  DISEASE,"  "  LETTERS  ON  CHEMISTRY," 
"  FIRST"  AND  "  SECOND   SERIES,"  "  CHEM- 
ISTRY OF  FOOD,"  ETC.,  ETC. 


FROM  THE  TENTH  LONDON  EDITION,  REVISED  AND  CORRECTED 


J3 1)  i  I  a  b  c  I  p  I)  i  a : 

T.  B.  PETERSON,  NO.  102  CHESTNUT  STREET, 


CONTENTS. 


PAGE 

Development  of  the  Natural  Sciences 5 

Special  Laws  of  Nature 6 

General  Laws  of  Nature 5 

Course  of  Investigation 6 

Preconceived  Views,  an  Impediment  to  Investigation 6 

Physiology  as  a  Deductive  Science 7 

Investigation  pursued  according  to  Physiological  Laws ; 7 

The  Difference  between  the  Chemistry  of  the  present  Day  and  that  of  an  earlier  Age 8 

Point  of  view  assumed  by  many  Physiologists  of  the  present  Day 8 

'    Confusion  of  Effect  :md  Cause • 8 

False  Explanation  of  Physical  Properties , ••  •  •     9 

v   -<r*very  Phenomena  of  Nature  is  dependant  on  mpre  than  one  Cause  9 

Chemical  Combination 10 

Different  Effects  of  Heat • 10 

The  Separation  of  Vital  Effects,  and  the  Chief  Requisites  thereto 10 

Continued  Disregard  of  these  Principles 10 

Examples  11 

Indefinite  Ideas  of  Irritability  and  Irritants 11 

False  Analogies 11 

Typical  Force — an  Indefinite  Idea 12 

Light  considered  as  an  Irritant    12 

Sound  as  an  Irritant    12- 

False  Idea  of  Reaction 13 

Verbal  Explanation  no  Advance 13 

y-lxerciso  of  the  Imagination  with  reference  to  Observation    14 

**-•  Error  originates  in  false  Observations  and  Combinations 14 

Observation • 15 

-  Examples  of  Erroneous  Observations — the  supposed  Influence  of  the  Moon  upon  the  Formation  of  Dew  15 

The  Influence  of  the  Atmospere  upon  Evaporation 15 

Dilution  of  the  Oxygen  of  the  Atmosphere  by  Nitrogen 15 

The  Power  of  the  Sun  in  attracting  Water 16 

The  Idea  of  Boerhave  on  the  Origin  of  Alkalis  in  Plants 16 

False  Comparison  between  the  Cohesive  Force  of  Crystallization  and  the  Organic  Force 16 

Explanation 17 

Comparison  of  the  Parasite  Theory  with  the  Chemical  Theory  of  Contagion,  Miasma,  and  Putrefaction  •  17 

Influence  of  Mechanical  Motion  on  Crystallization v 18 

Influence  of  Mechanical  Motion  on  Crystallizing  .Solutions  of  Salts 18 

Influence  of  Mechanical  Motion  on  Sulphuret  of  Mercury,  Iodide  of  Mercury,  and  Iron 18 

Influence  of  Mechanical  Motion  on  the  Indication  of  Chemical  Affinity J8 

Heat  similar  to  the  Action  of  a  Mechanical  Force 19 

Influence  of  the  Condition  of  Chemical  Activity 19 

Influence  of  the  Condition  of  Chemical  Activity  upon  the  Capacity  of  Bodies  to  enter  into  Combinations  19 

In  fluence  of  the  same  Condition  upon  the  Capacity  of  Bodies  to  suffer  Decomposition 20 

Influence  of  a  similar  Condition  upon  Organic  Substances 20 

Decayed  Wood 20 

Relation  of  Urea  and  Hippuric  Acid  in  Urine 20 

Influence  of  the  Putrefaction  of  Wood  on  the  Oxidation  of  Hydrogen 20 

The  Fibrin  of  the  Blood  and  Yeast  act  similarly  towards  Binoxide  of  Hydrogen 21 

Relation  of  combined  Organic  Atoms  amongst  themselves 21 

Putrefaction 21 

Affinity  not  the  Cause  of  Putrefaction 21 

Decomposition  of  Arnygdulin  and  Asparagin  by  Putrefying  Substances 22 

The  Conversion  of  Starch  into  Sugar ,.  22 

The  bame  Effect  produced  by  Animal  Membrane 22 

-Fermentation  and  its  Properties 22 

Different  Desrees  of  Putrefaction,  and  their  Influence  upon  Fermentation 22 

Milk  of  Almonds  and  Sugar 22 

Casein  and  Suear 23 

Animal  Membrane  and  Sugar 23 

The  Influence  of  a  higher  Temperature  upon  Fermentation 23 

Fousel  Oil  from  Sucar 23 

Separation  of  the  Sugar,  similar  to  that  of  Acetic  Acid  occasioned  by  the  Action  of  Heat 23 

The  Property  of  causinsr  Fermentation  is  common  to  all  compound  organic  Atoms 23 

Causes  of  the  Change  of  Form  and  Property  of  Matter 24 

Continuance  of  the  Decomposition  24 

Antiseptic  Substances 24 

3 


CONTENTS. 


PAGK 

Relation  of  Arsenious  Acid  to  Membranes 24 

Extension  of  the  Processes  of  Putrefaction  and  Fermentation  in  the  Living  Animal  Body 25 

Facts 25 

What  is  to  be  understood  by  the  term  "Products  of  Disease" 25 

Antiseptic  Substances  retard  the  Extension  of  Contagion  and  Miasma 25 

Putrefaction  Processes  as  Causes  of  Contagious  Diseases 26 

Conclusions 26 

Power  of  Infection — in  what  it  consists 26 

A  Challenge  to  Investigation 26 

The  Parasite  Theory 27 

The  Itch : 27 

The  Itch  a  Contagious  Disease  propagated  by  an  Animal ••• 27 

Contagious  Diseases  not  communicated  by  Animalcules 28 

Parasites  in  Bodies  of  the  higher  Classes  of  Animals » * 28 

Muscardine 28 

Parasites  in  Animals  and  Plants *•*• •> 2g 

False  Views  of  the  Causes  of  Putrefaction  are  the  Foundation  of  the  Parasite  Theory 2g 

Fungi  and  Infusoria  do  not  occasion  Putrefaction 2g 

Opposition  between  Putrefaction  and  the  Process  of  Life 2g 

Fungi  and  Infusoria  are  subjected  to  Putrefaction,  Fermentation  and  Destruction So 

Fungi  and  Infusoria  are  the  Attendants,  but  not  the  Orginators  of  the  Process  of  Putrefaction 30 

Fungi  and  Infusoria  hasten  the  Process  of  Putrefaction  and  Corruption 3o 

By  this  Means  they  become  the  Enemies  of  the  Process  of  Putrefaction 3i 

The  Nature  of  Yeast Si 

Relation  of  the  Yeast  in  Solutions  of  Sugar,  in  Grape  Juice,  and  Beer  Wort 3i 

The  Formation  of  Yeast,  Alcohol,  and  Carbonic  Acid  are  mutually  Dependant  upon  each  other 83 

Vibriones  in  the  Urine 32 

Fungi  contain  Sugar 32 

Change  in  the  Process  of  Putrefaction  in  Heated  Air 32 

Two  simultaneously  occurring  Phenomena  are  frequently  held  to  be  a  Cause,  and  its  Effect 33 

Examples * 33 

A  Storm  regarded  as  the  Cause  of  unusual  Changes  in  the  State  of  the  Barometer 34 

Symtoms  of  Fever  must  not  be  regarded  as  the  Causes  from  whence  it  arises     • 34 

Henle's  Explanation  of  Fever 34 

What  Course  must  be  pursued  in  the  Investigation  of  the  Cause  of  Fever 34 

Point  of  View  of  the  Investigation 35 

Inquiry  into  the  Connection  of  the  Spinal  Cord  with  the  Effects  of  Motion 35 

Regular  and  Irregular  Motion 35 

Relation  of  the  Phenomena  of  Animal  Heat  to  those  of  Motion 36 

Relation  of  the  Phenomena  of  Heat  to  the  Oxygen  of  the  Air 36 

Erroneous  Conclusions  drawn  from  bringing  one  Cause  too  prominently  Forward 37 

Correction  of  Schleiden's  View 37 

The  Means  by  which  Motion  occurs    - 37 

First :  By  the  Communication  of  a  Moving  Mass 37 

Secondly :  By  an  Attractive  or  Repulsive  Force • 38 

Chemical  Processes,  as  Phenomena  of  Motion,  belong  to  the  second  Kind 38 

Putrefaction  and  Fermentation  belong  to  the  first  Order  of  Phenomena  of  Motion 38 

The  Force  of  Gravitation  gives  no  Rise  in  itself  to  Motion 38 

Want  of  Correctness  in  Expression,  the  Cause  of  Erroneous  Conclusions  and  Misunderstandings 38 

Examples 39 

Point  of  Contact  between  Physiology  and  Chemistry 39 

— "Deviation  of  Chemical  and  Mechanical  Laws  from  the  Laws  which  govern  vital  Phenomena   3§ 

Relation  of  the  Properties  of  Elements  to  the  Properties  of  their  Combinations 39 

The  Chemical  Forces  of  the  Elements  have  a  Share  in  the  Vital  Properties 40 

The  Relations  between  chemical  and  vital  Effects  must  be  investigated 40 

The  Relation  of  the  Weights  of  the  Elements  to  Chemical  Combinations 40 

The  Universality  of  Laws  of  Mutual  Dependance  in  Natural  Phenomena 40 

The  Way  to  attain  to  a  Knowledge  of  the  Relations  of  Dependance 41 

Examples  of  the  Laws  of  Dependance — Pressure  and  the  Boiling  Point   41 

The  Boiling  Point 41 

The  Law  of  the  Relations  of  Dependance  is  Distinct  from  the  Causes  by  which  these  Phenomena  are 

effected 42 

The  Boiling  Point,  the  Specific  Gravity,  and  the  Composition  of  a  Body  stand  in  the  Relations  of  Depen- 
dance to  each  other -. 42 

Specific  Heat  and  Atomic  Weight 42 

Specific  Heat  and  Tone  of  Gases 43 

Electricity  and  Magnetism,— Macnetism  and  Heat,— Magnetism  and  Chemical  Force 44 

Vital  Properties  are  no  Exception  to  a  Law  of  Nature - 4-' 

Anatomy  most  essential 45 

Anatomy  not  alone  sufficient 45 

What  must  be  superadded • ~  • 45 

Chemistry  alone  is  not  sufficient 45 

What  ia  meant  by  Chemical  Force 46 

Relations  of  Dependance  cannot  be  established  by  a  Numerical  System 46 

Numbers  are  only  Expressions  of  the  Relations  of  Dependance 46 

Chemical  Relations  between  Urea,  Uric  Acid,  Allantoin,  and  Oxalic  Acid 46 

The  Method  pursued  by  Chemistry  to  express  these  Relations 47 

What  is  meant  by  Chemical  Formulae 47 

Importance  of  Formulae 47 

Reasons  for  the  Chemist  to  Study  the  Products  of  Decomposition  of  a  Body • 48 

Misuse  of  Formulas • 48 

Hopes 48 


CHEMISTRY    AND    PHYSICS 


IN  RELATION  TO 


PHYSIOLOGY  AND  PATHOLOGY, 


DEVELOPMENT  OF  THE  NATURAL  SCIENCES. 

THE  history  of  science  teaches  us,  that  every  branch  of  physics  comprised  at  its 
commencement  nothing  beyond  a  series  of  observations  and  experiments,  whitfy  \  ,  . 

/ 


had  no  obvious  connection  with  each  other. 


SPECIAL  LAWS  OF  NATURE. 

All  advances  in  science  were  dependant  upon  the  discovery  of  new  facts,  by 
which  two  or  more  previously  observed  experiments  were  made  to  bear  upon  each 
other.  The  first  step  gained  was  the  deduction  of  special  laws,  which  embraced 
in  themselves  the  connection  of  a  certain  number  of  natural  phenomena  ;  the  next 
was  the  attainment  of  general  laws,  or  what  was  the  same  thing,  of  certain 
expressions  of  the  dependence  or  connection  of  a  larger,  or  smaller  series  of 
experiments. 


GENERAL  LAWS  OF  NATURE. 

Many  branches  of  physics  as  mechanics,  hydrostatics,  optics,  acoustics,  the 
theory  of  heat,  &c.,  have  been  elevated  to  the  rank  of  abstract  sciences,  in  conse- 
quence of  their  permitting  all  known  cases  of  the  phenomena  of  motion,  air, 
sound,  heat,  &c.,  to  be  traced  through  a  series  of  syllogisms  to  certain  truths,  or  to 
a  very  small  number  of  undoubted  facts,  which  not  only  unite  together  those 
already  known,  but  also  those  yet  remaining  to  be  discovered;  so  that  a  new  iso- 
lated series  of  conclusions  is  not  requisite  to  the  explanation  of  new  phenomena, 
or  experiments. 

If  we  can  regard  it  as  undoubted  that  not  only  the  phenomena  of  inanimate 

(5) 


CHEMISTRY  AND  PHYSICS  IN  RELATION 


nature,  but  also,  those  of  animal  and  vegetable  life,  are  peculiar  to  themselves, 
stand  in  certain  relations  to  each  other,  and  depend  upon  certain  causes ;  and  if 
farther,  it  be  true  that  it  is  only  by  a  knowledge  of  these  causes  or  conditions  that 
wfc  can  gain  a  clear  insight  into  the  existence  of  organic  processes,  then  must  tht 
investigation  of  the  reciprocal  dependence  and  the  conditions  of  the  phenomena  of 
Jife,  be  regarded  as  the  most  important  department  of  physiology. 
j  The  explanation  of  many  natural  phenomena,  requires,  in  most  cases,  nothing 
more  than  an  acquaintance  with  the  relaJiojLuf._dependence  in  which  they  stand, 
one  to  the  other. 

The  knowledge  of  these  relations  is  attainable  in  every  branch  of  natural 
investigation  by  the  extension  of  experience,  and  by  correctness  of  observation  ; 
and  there  can  be  no  question  that,  at  some  future  time,  as  chemistry  loses  the 
character  of  an  experimental  art,  so  will  physiology  be  capable  of  ranking  as  a 
deductive  science. 


COURSE  OF  INVESTIGATION. 

If  it  follow,  according  to  the  course  of  natural  investigation,  that  general  laws 

must  be  preceded  by  those  that  are  merely  special,  and  it  be  granted  that  a  just 

conception  of  life    cannot  be    acquired   without   a  thorough   knowledge   of   the 

]  organim  in  all  its  parts,  both  with  reference  to  the  functions  of  individual  organs 

I  in   themselves,  and   their  ^girUi^Ljlependence,  including  the  consideration  of  the 

^relation  of  form  to  organic  matter ;  tKen  it  will  not  be  denied  that  we  are  still 

most  widely  removed  from  the  possession   of  a  general  formula,  embracing  the 

comprehension  of  life,  and  the  knowledge  of  the  causes  and  connections  existing 

in  natural  phenomena.     So  remote  is  this  object,  that  there  are  many  who  still 

regard  the  probability,  or  even  possibility  of  the  attainment  of  such  general  laws 

in  physiology,  as  purely  chimerical ;  while  most  persons  are  unable  to  distinguish 

psychical  from  corporeal  phenomena,  or  the  idea  of  vital  power  from  the  form  of 

living  organs. 


PRECONCEIVED  VIEWS,  AN  IMPEDIMENT  TO  INVESTIGATION, 

A  man  even  of  the  most  cultivated  mind  cannot  wholly  emancipate  himself 
from  the  dominion  of  those  laws,  on  which  his  powers  of  comprehension  are 
dependant.  If  the  daily  experience  of  a  prolonged  period  constantly  show  him 
two  phenomena  or  facts,  apparently  closely  connected  together,  if  he  learn  that, 
for  centuries,  they  have  been  considered  inseparable,  and  if  he  have  never,  either 
by  accident  or  design,  been  led  to  consider  each  individually,  he  becomes  gradually 
incapable,  in  spite  of  the  greatest  exertion  to  the  contrary,  of  considering  them 
apart,  until  at  length  his  mind  refuses  to  admit  the  very  assumption  of  any  difference 
existing  in  the  nature  of  the  phenomena  observed. 

Innumerable  instances  testify  that  even  the  most  accurate  observers  of  their  age 
have  regarded  certain  facts  or  representations  as  impossible,  simply  because  their 
power  of  comprehension  was  unable  to  receive  them  ;  while  their  successors  have 
not  only  comprehended  them,  but  what  is  far  more,  have  universally  received  them 
as  incontestible  truths. 

Men  of  the  clearest  discernment,  who  were  raised  far  above  ordinary  ideas, 
were  yet  unable  to  understand  that  the  force  of  gravity  acts  with  an  upward 
instead  of  a  downward  tendency,  or  that  the  sun  from  its  vast  distance  could  exer- 
cise any  influence  upon  the  earth,  or  the  earth  upon  the  moon.  Even  the  great 
Leibnitz  rejected  the  Newtonian  theory,  because  he  could  not  regard  it  as  possible 
that  the  planets  could  maintain  a  motion  in  a  curved  line  around  one  common 
centre,  without  the  agency  of  some  continuously  acting  mechanism  ;  since  accor- 


TO  PHYSIOLOGY  AND  PATHOLOGY. 


ding  to  him  in  the  absence  of  a  propelling  power,  the  body  must  fly  off  at  a 
tangent  to  its  orbit. 

Starting  from  the  general  proposition  that  a  body  qan  exercise  no  influence  upon 
a  point,  with  which  it  is  not  in  contact,  the  Newtonian  theory  of  gravitation  was 
rejected ;  and  the  fact  now  become  familiar  to  the  mere  schoolboy,  that  the  power 
of  gravitation  is  active  at  boundless  distances  without  any  influencing  material 
agent,  appeared  even  to  men  of  the  noblest  intellect  to  contain  so  great  a  contra- 
diction, that  rather  than  receive  it,  they  maintained  the  probability  of  the  strange, 
and  unfounded  creations  of  their  own  fancy. 

There  are  many  theories  in  mechanics  and  physics,  which,  although  we  know 
to  have  been  regarded  as  the  great  discoveries  of  their  age,  and  the  results  of  the 
most  patient  and  laborious  investigations,  appear  to  us  now  so  true  and  obvious, 
that  if  we  did  not  possess  the  history  of  their  gradual  development,  it  would  seem 
incredible  that  a  doubt  of  their  truth  could  ever  have  been  entertained  by  any 
individual  in  any  age. 

The  simple  position  that  a  body  once  put  in  motion,  could  traverse  space,  for- 
ever pursuing  with  unvarying  velocity  the  same  direction,  appeared  so  opposite  to 
common  and  evident  experience  that  the  recognition  and  establishment  of  its  truth 
met  for  a  long  period  with  the  greatest  opposition. 

That  two  chemico-active  bodies  can  form  a  combination  of  definite  unchange- 
able properties,  through  their  union  in  indefinite  or  unlimited  proportions,  appears, 
even  to  our  sound  powers  of  comprehension  to  be  untenable. 

The  comprehensive  has,  as  we  have  shown,  nothing  to  do  with  the  apparent, 
but  is  dependant  upon  the  condition  of  our  mental  development.  If  the  uniting 
link  that  associates  a  fact  with  the  usual  counse  of  our  ideas  be  wanting,  the  fact 
itself  will  appear  devoid  of  truth  antl  comprehensibility.  This  is  one  of  the 
greatest  impediments  that  stands  in  the  way  of  the  application  of  chemistry  to 
psychology,  and  of  a  simple  consideration  of  chemical  discoveries  on  the  part  of 
many  physiologists ;  and  if  to  this  be  associated,  as  in  pathology,  the  assumption 
of  facts  on  experience,  the  correctness  of  which  has  no  other  foundation  than  the 
opinion  of  many  centuries,  and  if,  in  these  branches  of  science,  the  mode  of  arriv- 
ing at  conclusions  and  deductions  be  not  changed,  there  is  no  hope  as  yet,  that 
chemistry,  with  all  her  advances,  will  ever  be  able  to  render  any  essential  aid  to 
physiology  and  pathology  ;  while  it  is  alike  impossible  for  either  of  these  sciences 
to  attain  to  any  scientific  basis,  without  the  co-operation  of  chemistry  and  physics. 
While  no  one  doubts  the  necessity  of  this  co-operation,  there  is  little  unity  of 
sentiment  regarding  its  practical  application. 


PHYSIOLOGY  AS  A  DEDUCTIVE  SCIENCE. 

The  opinion  that  every  empirical  science,  including  physiology,  may,  in  the 
course  of  time,  acquire  the  character  of  a  deductive  science,  seems  to  require  no 
confirmation;  and  it  must  be  immaterial  whether  this  position  be  attained  by  bor- 
rowing from  other  sciences:  as  for  instance,  in  the  case  of  astronomy,  which  owes 
its  scientific  basis  to  its  partial  incorporation  with  the  theory  of  motion. 


INVESTIGATION  PURSUED  ACCORDING  TO  PHYSIOLOGICAL  LAWS. 

If  we  bear  in  mind  that,  as  no  occurrence  in  the  world,  so  also  no  phenomenon 
of  nature,  either  in  the  animal  or  vegetable  kingdom,  can  appear  without  standing 
in  relation  to,  or  as  the  immediate  result  of  another,  that  has  preceded  it ;  (as  the 
present  condition  of  a  plant  or  animal  is  dependent  upon  certain  pre-existing  con- 
ditions ;)  it  is  clear,  that  if  all  the  causes  that  affect  one  condition  and  their  in- 
fluence upon  time  and  space,  with  their  properties,  are  known  to  us,  we  shall  be 


CHEMISTRY  AND  PHYSICS  IN  RELATION 


able  to  declare  what  other  condition  will  succeed  the  former  one.     The  expression 
of  these  conditions  or  relations,  is  what  we  term  a  natural  law. 


THE  DIFFERENCE  BETWEEN  THE  CHEMISTRY  OF  THE  PRESENT 
LAY  AND  THAT  OF  AN  EARLIER  AGE. 

No  one  who  is  conversant  with  the  history  of  the  development  of  chemistry, 
and  of  many  other  branches  of  physics,  will  deny  that  the  main  reason  of  the 
advance  of  these  sciences  rests  upon  the  gradually  confirmed  conviction  that  every 
natural  phenomenon  has  more  than  one  requirement,  every  effect  more  than  one 
cause,  and  that  it  is  the  simple  inquiry  into  the  plurality  of  these  conditions,  and 
the  separation  of  effects  which  distinguish  the  chemistry  of  the  present  day  from 
that  of  former  times.  A  speedy  termination  was  put  in  the  period  of  phlogosis 
to  all  research  by  assuming  principles  of  dryness  and  humidity,  heat  and  cold, 
combustibility,  acidity,  volatilization,  &c. ;  ascribing  a  special  essence  to  every 
property,  the  explanation  of  which  was  included  in  the  simple  description  of  the 
phenomenon. 

The  fluctuation  in  weight  which  bodies  manifest  on  being  submitted  to  chemical 
processes,  was  regarded  as  a  property  of  matter  similar  to  the  effervescence  of 
limestone,  when  acted  upon  by  acids.  There  was  a  theory  for  the  respective 
phenomena  of  combustion  and  calcination,  although  the  relations  of  weight  were 
not  regarded  as  in  the  province  of  earlier  chemistry.  It  was  left  to  physiologists 
to  explain  how  a  body  could  have  an  increase  of  weight  after  losing  one  of  its 
constituents ;  and  further,  how  under  any  -circumstance,  a  body  can  show  a  fluc- 
tuation in  weight.  The  increase  of  weight  in  calcination  was  an  accidental  pro- 
perty, peculiar  as  it  was  supposed,  together  with  many  others,  to  metals. 

POINT  OF  VIEW  ASSUMED  Bf  MANY  PHYSIOLOGISTS  OF  THE 

PRESENT  DAY, 

Many  physiologists  and  pathologists  still  regard  the  conception  of  vital  processes 
and  phenomena,  from  the  same  point  of  view  as  the  phlogistics ;  they  ascribe  the 
effects  of  the  nervous  system  to  a  nervous  force ;  while  vegetation,  irritability, 
sensibility,  action  and  reaction,  simple  effects  of  motion  or  resistance,  causes  of 
the  formation  and  the  change  of  form,  which  are  included  in  the  expression  of 
typical  forces,  are  all  regarded  as  entities,  and  assume  the  place  occupied  in  older 
chemistry  by  the  essences. 


CONFUSION  OF  EFFECT  AND  CAUSE. 

The  most  common  phenomena  have  been  incorporated  in  the  minds  of  many 
physiologists  as  actual  capacities — properties — which  they  have  falsely  been  led 
to  explain  by  especial  reasons,  different  from  the  others  known ;  thus  the  terms 
endosmosis,  and  exosmosis,  have  been  applied  to  the  r^Hirn  to  a  state  of  equili- 
brium of  two  fluids  differing  in  their  nature,  or  of  two  unequally  dissolved 
substances,  separated  by  an  animal  membrane ;  and  thus  we  continue  to  treat 
names  as  if  they  were  facts,  embracing  an  explanation  of  the  process,  while  this 
phenomenon  is  nothing  more  than  a  filtration,  differing  so  far  from  other  forms, 
that  the  permeation  is  dependant  not  upon  pressure,  but  upon  attraction,  disposi- 
tion, or  affinity. 

To  this  mode  of  observation  was  added  the  equally  great  error  of  conceiving 
that  causes  must  be  of  a  similar  nature  to  their  results,  and  that  like  must  call 
forth  like.  Thus,  the  cause  of  combustion  was  thought  to  be  something  combus- 


TO  PHYSIOLOGY  AND  PATHOLOGY.  9 

tibie,  and  the  cause  of  acid,  something  acid  ;  the  caustic  property  of  burnt  lime 
was  derived  from  a  caustic,  which  suffered  itself  to  be  transferred  from  one  body 
to  the  other,  from  the  lime,  for  instance,  to  the  so-called  mild  alkalies  ;  the  pre- 
sence of  a  primitive  alkali  was  pre-supposed  in  the  alcalies ;  an  acidum  universale 
in  acids ;  a  primitive  salt  in  salts ;  while  analogous  bodies  were  varieties  of  one 
substance. 


FALSE  EXPLANATION  OF  PHYSICAL  PROPERTIES. 

Many  physical  properties  of  bodies  were  explained  by  the  physical  character 
of  their  most  minute  parts ;  thus,  for  instance,  a  sharp  taste  was  ascribed  to  sharp 
particles.  Lemery's*  view  that  the  smallest  atoms  of  an  acid  were  lance-shaped, 
and  that  the  atoms  of  alkalies  were  porous  like  a  sponge,  met  with  great  approval, 
for  it  seemed  to  confirm  their  mutual  power  of  neutralization ;  and  the  fact  of 
ammonia  precipitating  gold  in  its  solution  was  a  convincing  proof  to  the  chemists 
of  that  day,  of  the  capability  they  ascribed  to  ammonia  of  abrading  the  lance-like 
points  of  the  atoms ;  it  acted,  to  use  Lemery's  words,  like  the  cudgel  thrown  by 
a  boy  against  a  nut  tree  laden  with  fruit.  .  •.  v* 

Thus  certain  substances  which  possess  an  astringent  or  cooling  flavor,  were 
supposed  to  exercise  an  astringent  or  cooling  effect  upon  the  living  body  ;  and 
any  alcoholic  drink,  which  may  be  termed  strong  according  to  the  common  mode 
of  speech,  was  admitted  as  a  tonic  among  other  remedial  agents. 

It  is  an  error  to  suppose  that  this  mode  of  considering  natural  phenomena  be- 
longs to  a  very  remote  period,  as  will  be  seen  from  the  following  extracts  drawn 
from  Mulder's  "  Chemistry  of  vegetable  and  animal  Physiology. 't  "  We,  there- 
fore, rightly  conclude,"  he  observes,  "that  in  sulphur,  selenium,  chromium,  and 
manganese,  similar  forces  exist ;  and  thus  we  arrive  at  the  idea  that  the  chemical 
relations  of  these  elements  are  not  dependant  upon  their  matter,  but  upon  the 
analogous  forces,  by  which  their  molecules  are  governed.  Thus  the  idea  of  the 
matter  of  sulphur  is  associated  what  somewhat  of  the  idea  of  force,  and  of 
the  same  force  which  operates  in  selenium  also — which  operates  not  only  in 
forming  combinations,  but  in  contributing  likewise  to  the  formation  of  the  whole 
character  of  the  compound  substances  produced.  We  remark  the  effects  of  this 
force  which  exists  in  sulphur,  selenium,  &c.,  even  in  more  complicated  compounds 
than  those  to  which  we  have  referred." 

The  excellent  investigations  of  Mitscherlich  and  Kopp  upon  isomorphism,  have 
not  been  able,  as  we  see,  to  eradicate  this  mode  of  observation. 


EVERY  PHENOMENA  OF  NATURE  IS  DEPENDANT  ON  MORE  THAN 

ONE  CAUSE. 

The  truth  of  a  number  of  opinions  or  views,  whether  justly  or  unjustly,  is 
liable  to  be  doubted ;  but  a  phenomenon,  an  effect,  cognizable  to  the  sound  senses 
of  the  most  different  persons,  every  where,  and  at  all  times,  cannot  be  doubted, 
excepting  inasmuch  as  the  causes  which  bring  about  certain  results  may  not  be 
fully  known.  But  this  cause  can  never  be  supplied  by  the  imagination,  in  the 
department  of  natural  investigation;  for  we  know  that  one  and  the^same  effect,  as, 
for  instance,  a  mechanical  motion,  a  blister  upon  the  skin,  or  the  contraction  of  a 

*  Lemery's  opinions  were  first  promulgated  in  his  Cours  de  Chimie,  published  in 
1C75.  An  English  translation  entitled,  A  course  of  Chymistry,  containing  an  easy 
Method,  &c.,  passed  through  four  editions,  the  last  bearing  the  date  of  1720. 

f "  Versuche  einer  allgemeinen  physiologischen  Chemie."  Braunschweig,  1844,  p. 
37,  of  the  first  edition. 


10  CHEMISTRY  AND  PHYSICS  IN  RELATION 

muscle,  may  be  brought  about  by  different.causes,  and  that  one  and  the  same  cause 
may  bring  about  a  variety  of  effects. 


CHEMICAL  COMBINATION. 

We  know  that  the  simple  process  of  chemical  combination  is  dependant  upon  at 
least  three  causes  or  conditions,  which  must  stand  in  certain  relation  to  each  other, 
if  the  combination  is  to  be  formed,  and  that  affinity,  the  force  of  cohesion,  and 
heat,  have  an  equal  share  in  the  process. 


DIFFERENT  EFFECTS  OF  HEAT. 

We  know  further  that  when  a  given  quanity  of  heat  expands  a  solid  body,  and 
forces  its  minutest  parts  to  separate  from  each  other,  a  double  or  triple  quantity 
will  entirely  change  the  properties  of  the  body,  and  that  a  further  alteration  occurs 
in  these  properties  if  the  amount  of  heat  that  is  communicated  exceed  a  certain 
degree. 

It  is  perfectly  certain  that  expansion,  liquefaction,  and  transition  into  the  gaseous 
form  are  dependant  upon  causes,  identical  in  their  nature,  but  that  the  effects 
produced  are  by  no  means  proportional  to  the  causes ;  the  reason  of  this  has  been 
justly  sought  in  the  reaction  or  resistance  of  some  other  cause,  and  our  idea  of 
the  existence  of  the  power  of  cohesion  thus  acquires  a  more  scientific  basis. 

The  same  degree  of  heat,  which  is  a  condition  of  the  combination  of  the  oxygen 
of  the  air  with  mercury,  produces  the  opposite  effect — the  decomposition  of  the 
oxide  of  mercury  into  mercury  and  oxygen,  if  the  temperature  be  raised  a  few 
degrees. 

By  a  simple  process  of  oxidation  we  derive  acetic  acid  from  alcohol :  we  obtain 
this  acid  from  the  oxidation  of  salicylite  of  potash;  we  may  also  exhibit  it  from 
wood,  sugar,  and  starch,  by  the  mere  application  of  heat  and  the  exclusion  of  the 
oxygen  of  the  atmosphere :  in  all  these  cases  the  product  yielded  is  the  same  ;  but 
the  conditions  of  its  formation  are  extremely  different. 

THE  SEPARATION  OF  VITAL  EFFECTS,  AND  THE  CHIEF  REQUISITES 

THERETO. 

If  it  be  true  that  physiology  can  only  attain  to  a  scientific  basis  by  the  investi- 
gation of  the  plurality  of  conditions,  on  which  the  phenomena  of  life  depend ;  and 
if  it  be  granted  that  this  can  only  be  attained  by  a  consideration  and  separation  of 
vital  effects,  and  the  conditions  to  which  they  give  rise ;  it  is  evident  that  since  a 
number  of  causes  have,  or  may  have,  an  influence  upon  these  effects,  the  physiol- 
ogist ought  to  possess  an  intimate  knowledge  of  all  the  forces  and  causes  which 
may  bring  about  changes  of  form  and  character  in  matter ;  since,  without  this,  he. 
would  be  unable  to  separate  true  effects  from  those  which  might  be  erroneously 
ascribed  to  the  cause,  and  which,  perhaps,  have  nothing  in  common  with  indications 
of  gravity,  affinity,  &c. 


CONTINUED  DISREGARD  OF  THESE  PRINCIPLES. 

No  one  can  deny  that  these  principles  are  applied  in  the  investigations  of 
pathology  at  the  present  day,  and  the  difference  between  the  method  of  inquiry 
now  pursued  from  that  in  use  in  the  earlier  stages  of  philosophical  science  is 
cerUinly  \ery  great,  although  the  influence  of  the  older  system  is  not  quite  exier- 


TO  PHYSICS  AND  PATHOLOGY.  H 

minated,  at  least  as  far  as  Germany  is  concerned.  In  spite  of  our  acknowledg- 
ment of  the  accuracy  of  the  principles  of  natural  investigation,  we  are  but  too 
ready  to  throw  off  its  shackles,  and  suffer  our  unfettered  thoughts  wherever  the 
way  is  not  clear,  to  erect  a  barrier  of  errors  before  the  gates  of  knowledge. 
Favorite  antitheses  and  paraphases  still  play  a  chief  part  in  all  explanations, 
robbing  common  facts  and  conditions  of  the  simplicity  and  perspicuity  of  which 
they  are  capable.  The  deficiency  here  rests  not  with  the  principles,  but  in  the 
want  of  their  due  application. 


EXAMPLES. 

A  few  extracts  from  the  writings  of  a  distinguished  pathologist  of  the  present 
day  will  suffice  to  justify  these  remarks,  and  to  show  the  influence  that  the  older 
mode  of  investigation  still  exercises  upon  the  present ;  they  will  also  tend  to 
demonstrate  how  impossible  it  is  to  arrive  at  correct  conclusions  by  starting  from 
indefinite  ideas,  and  how  small  is  the  acquisition  of  scientific  knowledge  with 
reference  to  chemical  and  physical  sciences,  even  in  the  most  intellectual  men. 


INDEFINITE  IDEAS  OF  IRRITABILITY  AND  IRRITANTS. 

Many  external  causes,  as  the  atmosphere,  heat,  electricity,  magnetism,  chemical 
agents,  mechanical  pressure,  friction,  &c.,  exercise  certain  effects  upon  the  whole, 
or  parts  of  the  organism ;  in  some  cases  these  are  similar,  in  others  different. 

These  effects  are  dependent  upon  a  certain  number  of  those  active  causes,  which 
exert  either  an  external  or  internal  influence  upon  the  organism,*  l^he  existence 
of  these  causes  is  capable  of  being  defined  and  measured  by  the  "qualitative  and 
quantitative  difference  in  the  effects  produced  by  external  causes  which  indicate 
a  changed  condition.  The  active  forces  in  the  organism  are,  accordingly,  appre- 
ciable by  the  investigation  of  those  effects  which  are  qualitatively  and  quantita- 
tively modified  by  every  external  cause.  The  method  pursued  by  modern 
pathology  is  exactly  the  reverse  of  the  principles  advanced,  as  is  proved  by  a 
few  passages  from  the  celebrated  work  of  Henle,  "  On  Pathological  Investiga- 
tions."* "  Irritability  is,"  according  to  Henle,  "every  thing  which,  in  acting  upon 
organic  matter,  alters  its  form  and  composition,  and  consequently  its  function," 
p.  223.  Far  from  regarding  the  separation  of  causes  and  their  effects  as  the  indis- 
pensable auxiliaries  of  knowledge,  the  author  here,  as  we  perceive,  includes  all 
imaginable  causes  of  the  changes  in  the  form  and  properties  of  the  organic  body, 
under  the  term  irritability ;  and,  in  the  exposition  of  conditions,  this  word  plays 
the  part  of  an  entity,  although  this  does  not  comprehend  the  mode  of  action  of 
electricity,  heat,  light,  magnetism,  or  chemical  forces,  but  simply  a  small  part  of 
the  action  of  each  of  these  agents.  We  need  only  apply  to  the  following,  the 
definition  given  above  by  this  author,  to  perceive  how  little  science  gains  by  such  a 
method. 

"  Irritability  alters  the  nervous  fibre  and  its  relations  to  the  blood ;  but  if  it  do 
not  wholly  decompose  it,  the  metamorphosis  of  matter  continues,  and  is,  perhaps, 
even  increased  by  the  irritation,  &c." 


FALSE  ANALOGIES. 

No  one  after  this  will  wonder  to  find,  at  p.  221  of  the  same  work,  an  hypo- 
thesis regarding  the  mode  of  action  of  irritants,  although  there  is  not  an  illusion  to 

*  Pathologishe  Untersuchungen,  Berlin,1840. 


12  CHEMISTRY  AND  PHYSICS  IN  RELATION 

the   mode  of  action  of  any  thing,  or  cause,  which  in  acting  upon  organic  matter 
changes  its  form  or  composition. 


TYPICAL  FORCE— AN  INDEFINITE  IDEA. 

It  cannot  surely  be  correct  to  regard  certain  vital  indications,  (as,  for  instance, 
the  development  of  the  organism  from  the  egg  or  germ,  or  the  renewal  of  original 
forms,)  as  dependent  on  a  certain  typical  power  in  the  organism,  since  this  expres- 
sion is  nothing  but  a  mere  verbal  illustration. 

Henle,  at  page  129  of  his  "  Rationelle  Pathologic,"  admits  that  the  perpetual 
typical  laws,  which  he  has  spoken  of,  are  inadequate  to  explain  how  the  salaman- 
der can  regenerate  a  whole  limb,  while  in  the  kindred  frog  regeneration  is  limited 
to  a  few  tissues,  as  in  the  higher  animals  ;  and  regards  these  indications  as  proving 
nothing  more  than  the  fact  that  they  are  such.  To  comprehend  an  explanation, 
presupposes  a  knowledge  of  the  laws  on  which  it  depends,  and  the  comprehension 
of  the  law  is  inseparable  from  the  knowledge  of  qualitative  or  quantitative  re- 
lations. 

By  way  of  rough  illustration,  we  may  compare  the  healthy  organism  in  many 
respects  to  a  large  Transatlantic  steamboat ;  the  latter  consumes  at  every  moment 
of  its  passage  oxygen  and  fuel,  which  are  again  given  off  in  the  form  of  carbonic 
acid,  water,  soot,  or  smoke ;  it  encloses  sources  of  heat  and  power,  which  call 
forth  motor  effects,  and  minister  to  the  wants  of  the  crew,  by  preparing  food  for 
their  use.  If  a  sail  be  rent,  there  is  one  at  hand  to  repair  it ;  if  a  leak  be  sprung, 
the  joiner  is  there  to  arrest  the  damage ;  while  a  number  of  men  are  ever  active  in 
keeping  up  the  original  condition  of  the  vessel,  and  maintaining  her  speed ;  and  so 
it  is  with  the  living  body,  which  likewise  has  its  smiths,  and  joiners,  and  other 
artificers.  Let  it  then  be  our  duty  to  study  and  recognise  its  mutual  relations. 


LIGHT  CONSIDERED  AS  AN  IRRITANT. 

It  is  impossible  to  arrive  at  the  comprehension  of  a  subject,  if,  as  is  done  by 
some  pathologists,  a  term — such  as  an  irritant — be  made  to  include  alike  active 
causes,  which  change  the  form  and  composition  of  organic  bodies,  and  such  as 
light,  sound,  &c.,  which  do  not  possess  this  capacity.  Light  is  in  itself  a  motor 
appearance,  and  as  such  is  perceived  by  the  eye,  exciting  in  the  optic  nerve  a 
motion  which  is  transferred  to  the  sensorium  ;  the  motion  once  begun  is  continued, 
as  the  tones  of  a  flute  are  prolonged  in  the  air,  or  a  string  in  the  piano  produces 
tones.  The  impression  of  light  is  motion  itself,  but  this  motion  calls  forth  no 
change  in  the  form  and  composition  of  the  eye  or  brain,  unless  new  causes  are 
superadded  ;  and  among  such  we  may  rank  the  labor  of  thought,  by  which  the 
impression  is  converted  to  a  conscious  perception,  awakening,  in  its  turn,  concep- 
tions and  ideas. 

No  one  would  seriously  maintain  that  a  piece  of  white  paper  could,  by  its  re- 
flected light,  bring  about  a  change  in  the  form  and  composition  of  the  brain,  since 
an  opposite  effect  must  then  necessarily  be  ascribed  to  a  piece  of  black  paper, 
from  which  no  light  is  given  forth ;  but  the  two  combined,  the  black  and  white, 
when  in  the  form  of  letters  in  a  book,  awaken  the  most  manifold  feelings,  concep- 
tions, and  images ;  and  it  is  by  means  of  these,  and  not  of  light,  that  an  influence 
is  exercised  upon  the  properties  of  the  brain. 


SOUND  AS  AN  IRRITANT. 

The  observations  which  we  have  made  regarding  light,  apply  in  every  respect 


TO  PHYSIOLOGY  AND  PATHOLOGY.  13 

to  sound  ;  the  vibrations  of  the  air-wave  are  continued  through  the  organs  of  hear- 
ing, and  communicated  to  the  auditory  nerve.  The  motion  imparted  to  the  mem- 
brane of  the  typanurn  alters  its  form  and  composition  as  little  as  those  of  the  mole- 
cules, which  have  received  a  like  motion  from  it.  As  the  eye  wearies  in  a  picture 
gallery,  although  it  receives  less  light  in  the  same  period  than  it  would  in  the  open 
air,  so  it  is  also  with  the  ear. 


FALSE  IDEA  OF  REACTION. 

The  false  ideas  conveyed  by  a  mere  verbal  term,  give  occasion  to  constant  mis- 
conception. This  is  the  case  with  the  word  reaction,  which  merely  means  an 
opposing  agency,  but  is  used  in  physiology  in  a  very  different  sense.  We  say  that 
the  glands  react  upon  an  irritant,  if  the  secreting  power  be  increased  by  any  external 
cause,  as  is  perceptible  in  a  number  of  the  secretions  at  the  time  of  applying  an 
irritant.  One  peculiarity  of  organic  bodies  is,  that  the  increased  activity  of  the 
glands  does  not  continue,  even  if  the  irritation  be  kept  up ;  although  it  lies  in  the 
nature  of  things  that  the  secretion  must  cease  if  there  is  no  matter  present  capable 
of  affording  it,  and  that  it  will  be  again  augmented  in  proportion  to  the  new  supply. 
The  action  of  the  irritant  is  not  an  action  upon  the  glands,  but  upon  the  cause, 
which  equally  produces  the  secretion,  so  that,  in  consequence  oif  the  irritation, 
more  matter  is  secreted  at  one  period  than  at  another. 

Thus,  in  the  tail  of  a  lizard,  a  metamorphosis  and  renewal  of  its  molecules  is 
continually  going  on,  and  when  the  tail  is  cut  off,  and  the  cut  surfaces  are  separated, 
the  governing  forces  act  against  the  separation  of  the  parts  by  the  knife,  but  no 
counter  action  of  vital  force  is  exhibited  upon  the  knife.  The  cut  surface  of  the 
severed  piece  of  tail  is  not  renewed,  but  the  one  which  is  connected  with  the 
organism  grows,  not  in  consequence  of  a  reaction,  but  owing  to  the  continuance 
of  the  causes  which  effect  the  renewal.  The  body  of  the  lizard  is  not  integrally 
renewed,  when  nutrition  is  absent.  If  the  tail  grow  again,  the  other  parts  of  the 
body  lose  a  corresponding  weight  and  volume. 

The  organic  body  resembles  other  bodies  in  all  its  conditions ;  thus  many  effects 
which  have  been  called  forth  continue,  even  when  the  causes  which  gave  rise  to 
them  have  ceased  to  act;  others  are  balanced,  if  the  active  cause  of  the  disturbance 
cease,  because  within  the  body  itself  there  are  forces  or  causes  of  resistance  at 
work  which  uninterruptedly  make  themselves  felt. 
t  - 

VERBAL  EXPLANATION  NO  ADVANCE. 

The  very  small  amount  of  knowledge  we  have  gained  from  that  period  of  phy- 
siology, when  it  was  looked  upon  as  a  mere  natural  philosophy,  sufficiently  proves 
that  the  most  comprehensive  description  of  a  function  of  the  organic  body,  as  the 
process  of  respiration  or  digestion,  or  a  condition  of  disease,  is  not  sufficient  to 
impart  a  knowledge  of  it,  and  that  the  most  ingenious  combinations  contribute 
nothing  to  our  advance,  if  they  be  not  sustained  by  a  close  and  accurate  inquiry 
into  facts  already  observed,  and  such  as  yet  remain  to  be  brought  to  light.  The 
imaginative  faculty  alone  does  not  justify  us  in  losing  sight  of  the  original  point 
of  view,  nor  in  assuming  that  a  consecutive  course  of  views  and  opinions  is  an 
advance  in  science,  since  such  a  mode  of  proceeding  can  only  be  compared  to 
that  of  a  man  revolving  in  a  circle,  and  seeking  to  gain  the  greater  number  of 
different  points  of  view.  Not  that  these  are  immaterial,  for  they  indicate  the  direc- 
tion in  which  we  must  apply  our  powers;  but  the  mere  description  of  a  condition, 
as  for  instance,  of  a  catarrh  being  an  inflammation  of  the  mucus  membrance  of 
the  nose,  must  not  be  regarded  as  an  explanation,  or  as  the  termination  to  our  in- 


14  CHEMISTRY  AND  PHYSICS  IN  RELATION 

quiry.     A  new  expression  for   catarrh,  as  arising  from  some  active  injury  to  the 
cutaneous  nerves,  is  no  actual  again,  but  a  mere  ideal  representation. 


EXEECISE  OF  THE  IMAGINATION  WITH  REFERENCE 
TO  OBSERVATION. 

The  right  use  of  our  senses — as  in  the  appreciation  of  the  distance,  or  height, 
or  circumference  of  a  body — is  acquired  by  experience  and  reflection,  and  so  also 
is  the  right  conception  of  a  natural  phenomenon ;  and  the  reflection  of  it  in  all 
its  purity,  undimmed  by  the  representations  awakened  during  our  perception  of  it, 
is  the  attribute  of  a  well  trained  mind.  The  botanist  recognizes  at  a  glance  the  ex- 
istence, and  the  varieties  of  the  plants  around  him  :  the  painter  sees  a  multitude  of 
points  which  the  unskilled  eye  cannot  detect  even  after  the  most  fixed  attention. 
None  of  the  experimental  sciences  demand  this  acuteness  and  exercise  of  the 
imaginative  faculty  more  strongly  than  physiology  and  pathology ;  and  in  few  is 
it  more  rarely  met  with  than  in  medicine.  Hence  arise  the  many  contradictions 
in  the  comprehension  of  the  Amplest  conditions,  and  the  close  succession  of  the 
most  opposite  modes  of  cure,  and  the  constant  appearance  and  speedily  forgotten 
existence  of  numerous  works  on  the  unhealthiness  of  certain  localities,  on  the 
nature  of  yellow  fever,  cholera,  and  the  plague — works  that  have  often  been  written 
by  men,  who  never  saw  the  place  they  describe,  or  a  single  case  of  any  of  the 
diseases  they  profess  to  treat  of.  In  order  to  give  validity  to  a  theoretic  view  of 
chemistry  and  physics,  it  is  indispensable  that  its  truth  be  guaranteed  by  a  series 
of  practical  investigations  on  the  part  of  the  writer.  If  this  be  wanting,  the  theory, 
although  it  may  be  the  perfectly  correct  expression  of  a  truth,  will  meet  with  little 
or  no  attention.  It  required  the  keen  imaginative  faculty  of  a  Berzelius  to  save 
from  utter  disregard  such  a  theory  as  that  advanced  by  Richter*  on  chemical  pro- 
portions, and  to  recognize  the  innate  truth  and  existence  of  a  common  law  of  com- 
binations amid  a  mass  of  false  facts  ;  among  which,  that  single  one,  which  forms 
the  starting  point  for  the  table  of  equivalents — the  nonexisting  carbonate  of  alumina 
— was  sufficient  to  destroy  all  faith  in  the  others. 


ERROR  ORIGINATES  IN  FALSE  OBSERVATIONS  AND  COMBINATIONS. 

Viewed  with  reference  to  natural  inquiry,  every  erroneous  mode  of  investigation 
depends  upon  the  want  of  just  observations,  and  the  false  conceptions  we  deduce 
from  them ;  and  is  further  based  upon  the  error  of  considering  the  simultaneous 
occurrence,  and  concurrence  of  two  phenomena  as  the  proof  of  the  existence  of  a 
connection  between  them.  In  nature  numerous  phenomena  occur,  of  which  one 
may  be  inappreciable,  if  another  given  one  fail,  while  again  innumerable  other 
phenomena  may  occur  together,  or  simultaneously,  without  standing  in  any  mutual 
relation  to  each  other.  The  assumption  of  an  erroneous  connection  of  this  kind, 
originates  in  all  cases  in  a  false  mode  of  investigation  ;  and  thus  the  combination  of 
two  phenomena,  only  similar  in  some  one  particular  relation,  is  always  the  result 
of  incorrect  observation. 

*  Richter's  work  entitled.  "  Anfangsgriinde  der  Stochyometrie,  oder  MessJcunst  chy- 
mischer  Elemenle."  (Elements  of  Stochyometry,  or  the  Mathematics  of  the  Chemical 
Elements,)  was  published  in  1792.  Its  object  was  a  rigid  analysis  of  the  different  salts, 
founded  on  the  fact  that  when  two  salts  decompose  each  other,  the  salts  newly  formed 
are  neutral  as  well  as  those  which  have  been  decomposed.  He  endeavored  to  de- 
termine the  capacity  of  saturation  of  each  acid  and  base,  and  to  attach  numbers  to 
each,  indicating  the  weights  which  mutually  saturate  each  other. 


TO  PHISIOLOGY  AND  PATHOLOGY.  15 


OBSERVATION. 

To  see  and  perceive  by  the  senses  is  a  condition  of  observation,  but  sight  and 
perception  do  not  characterize  observation. 

Observation  is  not  limited  to  seeing  the  thing  itself,  but  likewise  the  parts  of 
which  it  is  composed ;  thus  a  good  observer  must  perceive  and  seek  to  become 
conscious  of  the  mntnal^onn.ection  existing  between  the  several  parts  among 
themselves,  and  c^nsiSeredwith  reference  to  the  whole. 


EXAMPLES  OF  ERRONEOUS  OBSERVATIONS— THE  SUPPOSED  INFLU- 
ENCE OF  THE  MOON  UPON  THE  FORMATION  OF  DEW. 

One  of  the  most  familiar  illustrations  of  erroneous  observation,  is  the  influence 
ascribed  to  the  moon  in  reference  to  the  cold  felt  in  moonlight  nights,  and  to  the 
formation  of  dew  and  hoar  frost,  while  the  moon  in  these  cases  is  a  mere  spectator 
of  their  formation. 

In  a  work,  in  other  respects  very  good,  published  at  Dresden  last  year,  on  the 
influence  of  the  moon  upon  earth,  the  following  passage  occurs : 


THE  INFLUENCE  OF  THE  ATMOSPHERE  UPON  EVAPORATION. 

"  In  the  absence  of  an  atmosphere  we  cannot  conceive  the  existence  of  water, 
or  any  similiar  fluid  in  a  liquid  form.  If  our  globe  were  suddenly  deprived  of  air, 
its  rivers  and  seas  must  evaporate,  and  the  whole  earth  would  in  a  short  time  dry 
up,  as  we  see  exemplified  on  a  small  scale  by  experiments  under  the  air  pump." 
Here,  as  we  see,  a  connection  between  the  atmosphere  and  evaporation  is  presup- 
posed, which  does  not  exist  in  nature.  Without  an  atmosphere  it  is  true  no  clouds 
would  be  formed,  liquid  water  would  not  be  converted  into  vesicles  of  vapor,  and 
aqueous  vapor  would  not  rise  to  so  great  a  height;  but  the  atmosphere  has  no 
effect  upon  evaporation,  and  an  equal  quantity  of  aqueous  vapor  is  produced  under 
the  receiver  of  the  air  pump,  whether  or  not  the  air  be  exhausted." 


DILUTION  OF  THE  OXYGEN  OF  THE  ATMOSPHERE  BY  NITROGEN. 

We  find  in  many  physiological  works  the  view  advanced,  that  the  nitrogen  of 
the  atmosphere  contributes  to  the  dilution  of  the  oxygen,  and  the  modification  of 
its  action  upon  the  organism  ;  while  in  fact  the  quantity  of  oxygen  in  a  given 
space  would  not  in  any  respect  be  changed,  were  we  to  assume  that  the  nitrogen 
had  suddenly  been  removed  from  the  earth.  Two  gases  varying  in  their  nature 
exercise  a  certain  pressure  upon  the  human  body  and  the  surface,  with  which  it  is 
brought  in  contact;  but  the  particles  of  the  one  gas  do  not  compress  those  of  the 
other.  If  we  take  two  bottles,  one  filled  with  nitrogen,  and  the  other  exhausted, 
and  bring  them  in  contact  by  a  glass  tube,  the  nitrogen  will  distribute  itself  through 
both  vials;  if  again  both  bottles  are  of  equal  volume,  both  will  contain  an  equal 
amount  of  gas,  and  the  same  thing  happens  when  one  vial  instead  of  being 
exhausted  is  filled  with  oxygen  at  an  equal  pressure  ;  the  nitrogen  will  distribute 
itself  in  the  bottle  as  if  no  oxygen  were  present — the  action  of  oxygen  similar  to 
that  of  nitrogen. 


16  CHEMISTRY  AND  PHYSICS  IN  RELATION 


THE  POWER  OF  THE  SUN  IN  ATTRACTING  WATER. 

The  fact  of  the  impracticability  of  working  some  mines  in  the  height  of 
summer,  owing  to  the  veins  or  shafts  being  filled  with  water,  has  led  naturalists 
to  ascribe  to  the  beams  of  the  sun  a  power  of  attracting  water,  which,  according 
to  them  is  to  be  naturally  explained  by  the  action  of  the  sun  in  drying  up  the  soil, 
whence  hollow  spaces  are  formed  which  are  again  filled  from  below  by  capillary 
action.  We  know  that  a  connection  between  the  sun  and  the  water  takes  place 
within  the  mine,  but  this  simply  depends  upon  the  drying  up  of  the  brooks  in 
summer  ;  as  the  pumps  which  are  destined  to  draw  away  daily  an  equal  quantity 
of  water,  are  impeded  in  their  action  by  the  stoppage  of  supply  from  these 
sources. 

An  analogous  explanation  may  be  given  of  the  connection  between  the  immo- 
derate use  of  spirituous  liquors  and  self-combustion,  since  it  is  most  probable 
that  none  but  drunkards  would  be  likely  to  fall  into  the  fire,  and  be  thus  con- 
sumed. 


THE  IDEA  OF  BOERHAVE  ON  THE  ORIGIN  OF  ALKALIS  IN  PLANTS. 

The  false  ideas  concerning  vital  and  material  forces,  which  at  this  moment 
separate  by  an  unfathomable  abyss,  the  department  of  physiology  from  that  of 
chemistry,  arise  entirely  from  the  absence  of  true,  and  the  presence  of  erroneous 
views  ;  thus  the  ideas  entertained  in  the  eighteenth  century  of  the  occurrence 
of  alkalies  in  plants,  may  be  placed  side  by  side  with  those  entertained  in 
pathology  at  the  present  day  concerning  the  growth  of  a  crystal,  and  the  nutri- 
tion of  an  organic  being.  According  to  Boerhave  the  alkali  belonged  neither  to 
the  sap  nor  to  the  individual  parts  of  the  plant,  but  was  a  product  of  the  pro- 
cess of  combustion  ;  and  he  represented  to  his  hearers  that  decayed  wood  yielded 
no  alkali  which  was  as  little  a  constituent  of  the  plant  as  the  glass,  which  many 
plants  give  on  incineration. 

i 

FALSE  COMPARISON  BETWEEN  THE  COHESIVE  FORCE  OF  CRYSTAL- 
LIZATION AND  THE  ORGANIC  FORCE. 

"  Crystals  like  cells,"  so  says  Henle  in  his  (Rationelle  Pathologic,)*  "  are 
restricted  even  under  the  most  favorable  conditions  to  a  final  limit  of  growth, 
although  the  former  are  less  narrowly  circumscribed  than  the  latter.  Crystals 
associate  themselves  together  like  cells  in  aggregate  bodies,  reminding  us  by  their 
arborescent  arrangement  of  the  elementary  parts  in  the  higher  plants.  Material 
and  vital  bodies  offer  a  certain  measurable  degree  of  resistance  to  external 
influences,  but  accommodate  themselves  to  circumstances,  even  changing  their 
forms  occasionally.  The  most  remarkable  point  of  similarity  between  crystals 
and  organized  beings,  is  shown  after  injury  from  external  influences.  Crystals 
like  organic  bodies  have  the  power  of  regenerating  lost  parts  more  or  less  fully. 
In  both,  the  force  which  formed  the  body  continues  at  work,  independently  of  the 
matter  which  it  has  survived,  or  replaced.  Thus  if  a  crystal  from  which  the 
angles  have  been  cut  off  be  laid  in  a  fluid  whence  it  may  draw  a  substance 
analogous  in  composition  to  itself,  it  will  increase  generally,  but  more  especially 
in  the  direction  of  the  part  where  it  was  injured,  so  that  the  regular  figure  is  first 
restored,  just  as  an  injured  animal  will,  before  all  else,  regenerate  any  lost  part  as 
far  as  typical  laws  permit  regeneration  in  his  individual  case." 

*  Part  i.  p.  101. 


TO  PHYSICS  AND  PATHOLOGY.  17 

However  true  it  may  be  that  augmentation  in  the  mass  of  an  organic  body  be 
occasioned  by  the  force  of  attraction,  there  is  no  resemblance  externally  between 
the  growth  of  a  crystal  and  the  formation  of  an  organism.  The  form  of  the 
membrane  is  not  affected  by  the  physical  form  of  the  atom,  as  it  is  in  crystals,  for 
instance,  in  a  crystal  of  alum,  consisting  of  an  aggregate  of  particles  of  alum,  where 
each  individual  crystal  has  a  form  precisely  similar  to  that  of  the  aggregate  body 
The  cell  is  a  whole  within  itself,  and  not  an  aggregate  of  smaller  cells. 


EXPLANATION. 

Crystals  have  not,  like  cells,  a  limit  of  growth :  the  increase  of  size  in  the 
crystal  is  not  occasioned  by  a  cause  acting  from  within  in  an  outward  direction,  as 
in  living  organisms,  but  by  the  force  of  attraction  upon  the  surface.  This  force  is 
active  at  every  point  of  the  outer  surface,  while  the  molecules  below  take  no  part 
in  the  growth,  and  may  even  be  removed  without  depriving  the  superficies  of  their 
capacity  to  increase.  The  new  planes  which  are  formed  on  truncating  the  angles 
of  a  crystal,  exercise  no  stronger  attraction  on  the  molecules  of  the  surrounding 
medium,  than  do  the  other  planes ;  and  they  do  not  in  any  special  manner  perfect 
themselves. 

By  cutting  off  an  angle  from  an  octahedron  we  obtain  a  cubic  superficies  of  the 
crystal,  bounded  by  four  converging  octohedric  planes ;  in  a  crystalizing  fluid  the 
body  increases  in  three  dimensions ;  the  four  superficies  become  longer  and 
broader,  and,  in  consequence  of  their  elongation  and  convergency,  the  angle  is 
restored,  even  when  the  cubic  superficies  has  been  incrusted.  But  when  one  angle 
is  struck  off  a  cubic  crystal  of  alum,  and  the  crystal  be  thus  truncated,  it  does  not 
increase,  in  the  mother  liquid,  in  a  greater  degree  towards  the  truncated  angle  than 
towards  any  of  the  other  sides  ;  the  original  cube-like  figure  is  not  restored, 
because  the  force  of  attraction  of  one  individual  portion  of  a  cubic  plane  is  not 
greater  than  the  attractive  force  of  an  equally  large  portion  of  any  one  of  the  six 
superficies  of  the  outer  surface. 

A  crystal  which  grows  in  a  saturated  solution,  always  increases  on  one  side 
especially,  that  is,  on  the  surface  directed  towards  the  bottom  of  the  vessel,  owing 
to  this  plane  being  always  in  contact  with  those  particles  of  the  saline  solution, 
which  have  the  greatest  specific  weight,  and  are  most  copiously  charged  with  the 
crystallizing  matter.  There  are  also  cases  in  which,  in  consequence  of  the  differ- 
ence of  temperature  of  the  upper  surface  and  the  bottom  of  the  vessel,  the 
crystal  increases  most  in  a  downward  direction,  while  the  upper  parts  lose  their 
form. 


COMPARISON  OF  THE   PARASITE   THEORY  WITH  THE   CHEMICAL 
THEORY  OF  CONTAGION,  MIASMA,  AND  PUTREFACTION. 

The  source  of  the  most  frequent  errors  in  judging  of  a  condition  of  disease, 
originates  in  regarding  things  that  frequently  occur  simultaneously,  as  necessarily 
exercising  a  mutual  influence  on  each  other  ;  looking  upon  the  one  as  the  cause  of 
the  other.  For  the  comprehension  of  diseased  conditions  and  the  choice  of  means 
to  remove  them,  there  is  no  view  which  is  more  deficient  in  a  scientific  basis,  than 
that  of  identifying  miasma  and  contagion  with  living  organisms,  as  parasites,  fungi, 
and  infusoria ;  and  regarding  them  as  being  developed  and  increased  in  the  healthy 
body,  where  they  thus  induce  a  condition  which  may  terminate  in  death. 

A  glance  at  the  principles  of  the  parasite  and  chemical  theories,  will  suffice  to 
show  the  respective  merits  of  each. 

But  if,  in  the  following  remarks,  I  attempt  to  lay  before  my  readers,  by  means 
of  a  series  of  facts,  certain  processes  of  the  living  organism,  together  with  their 

2 


18  CHEMISTRY  AND  PHYSICS  H*  DELATION 

relation  to  certain  phenomena,  observed  in  inanimate  nature,  I  do  it  much  less 
with  the  desire  of  advancing  any  new  views  regarding  the  nature  and  substance 
of  contagion  and  miasma,  or  bringing  forward  the  question  of  fermentation  and 
putrefaction,  than  of  drawing  the  attention  of  naturalists  to  a  cause  which,  although 
hitherto  ill  observed,  is  one  that  prevails  generally,  wherever  a  change  occurs  in 
the  form  and  property  of  matter,  or  wherever  combination  and  decomposition  are 
going  on.  And  if  proof  be  adduced,  that  this  cause  exercises  a  decided  and  refer- 
able influence  upon  the  indication  and  direction  of  the  forces  of  cohesion  and 
affinity,  its  undeniable  share  in  the  actions  of  vital  force  will  be  the  less  ques- 
tioned, since  vital  force  belongs  to  the  same  category  as  chemical  forces,  as  far  as 
the  former  manifests  its  activity  only  by  direct  contact,  or  at  immeasurably  small 
distances. 


INFLUENCE  OF  MECHANICAL  MOTION  ON  CRYSTALLIZATION. 

Every  one  knows  that  water  freezes  at  all  temperatures  below  32°  F.,  and  that 
during  the  act  of  freezing  the  temperature  remains  at  32°  F. ;  nevertheless,  water 
may  be  cooled  as  low  as  5°  F.,  without  becoming  solid,  if  the  fluid  be  in  a  state 
of  perfect  rest.  The  least  disturbance  is  sufficient  to  effect  congelation. 

INFLUENCE  OF  MECHANICAL  MOTION   ON   CRYSTALLIZING  SOLU- 
TIONS OF  SALTS. 

The  same  conditions  affect  a  number  of  solutions  of  salts,  dissolved  by  heat; 
if  cooled  in  a  state  of  perfect  rest  they  do  not  precipitate  any  salts,  and  no  separa- 
tion occurs  between  the  water  and  the  dissolved  salt,  while  the  least  disturbance — 
a  particle  of  dust  or  a  grain  of  salt  thrown  into  the  water — will  induce  the  mole- 
cules thus  disturbed  to  crystallize,  and  when  once  crystallization  has  begun,  it  is 
continued  throughout  the  whole  mass. 

INFLUENCE   OF  MECHANICAL    MOTION   ON   SULPHURET  OF   MER- 
CURY, IODIDE  OF  MERCURY,  AND  IRON. 

By  constant  shaking  and  friction,  the  black  amorphous  suphuret  of  mercury  is 
converted  into  crystalline  cinnabar,  while  the  rough  iron,  whose  parts  are  irregu- 
larly deposited,  becomes  crystalline  on  being  hammered.  On  rubbing  a  portion 
of  lemon  colored  iodide  of  mercury,  it  passes  into  a  new  state  of  crystallization, 
and  becomes  scarlet. 

From  these  facts  it  is  shown  that  a  mechanical  motion  exercises  an  influence 
upon  the  indication  of  the  force  which  governs  the  condition  of  the  body,  and  this 
motion  is  continued  to  its  smallest  molecules ;  for  the  formation  of  crystals  it  is 
necessary  that  they  should  be  turned  towards  the  direction  in  which  the  force  of 
attraction  is  the  strongest;  it  is,  therefore,  clear  that  atoms  can  be  put  in  motion  in 
fluids,  as  well  as  in  solid  bodies,  by  a  stroke  or  blow,  by  frictic>n,  or  by  some  other 
meehanical  cause.  The  causes  do  not,  however,  exercise  a  certain  influence  on 
the  indication  of  the  cohesive  power  alone,  but  also  upon  the  chemical  affinity. 


INFLUENCE    OF   MECHANICAL    MOTION   ON   THE   INDICATION    OF 
CHEMICAL  AFFINITY. 

In  a  weak  solution  of  chloride  of  potassium,  tartaric  acid  does  not  deposit  any 
piecipitate :  but  mere  shaking,  or  the  friction  of  the  inner  wall  of  the  ves^H  *  "'**» 


TO  PHYSIOLOGY  AND  PATHOLOGY.  19 

a  glass  rod  instantly  causes  a  deposit  of  crystals  of  bitartrate  of  potash.  The  ful- 
minates of  silver  and  mercury  explode  with  the  greatest  violence  on  the  applica- 
tion of  a  blow,  or  of  friction  ;  the  same  is  the  case  with  Berthollet's  fulminate  of 
silver,  with  picrate  of  lead,  and  many  other  compounds.  It  is  clear  that  in  these 
cases  the  blow  or  friction,  or  more  correctly,  the  motion,  is  imparted  to  the  atoms 
of  these  combinations ;  that  the  direction  of  their  attraction  is  thereby  changed, 
and  that,  consequently,  new  products  are  formed.  Fulminate  of  silver  contains 
cyanic  acid.  By  the  blow  or  friction,  a  new  mode  of  arrangement  is  brought 
about :  a  part  of  the  carbon  developes  itself,  and  combines  with  the  oxygen,  form- 
ing carbonic  acid  ;  nitrogen  developes  itself  with  the  carbonic  acid,  and  explosion 
is  the  result  of  the  sudden  transition  to  the  gaseous  form.  The  colorless  fluid  sty- 
role  becomes  solid  and  hard  through  the  influence  of  a  purely  mechanical  motion. — 
(Sullivan.) 


HEAT  SIMILAR  TO  THE  ACTION  OF  A  MECHANICAL  FORCE. 

A  number  of  bodies  are  decomposed  by  heat,  and  in  these  cases  its  action  is 
perfectly  similar  to  that  of  a  mechanical  force.  Heat  acts  like  a  wedge  driven  in 
between  the  atoms.  If  between  two  atoms  the  resistance,  which  the  chemical 
force  that  held  them  together,  has  opposed  to  the  entrance  of  the  wedge  be  less 
than  the  force  which  separated  them,  the  atoms  fall  asunder,  and  decomposition  is 
the  result.  Oxide  of  mercury  is  resolved  into  oxygen  and  the  metal.  Heat  acts 
in  the  same  manner  on  bodies  composed  of  more  than  two  elements.  At  a  certain 
temperature  the  fulminates  of  silver  and  mercury,  Berthollet's.  fulminate,  and 
picrate  of  lead  explode.  Heat  alters  the  original  mode  of  arrangement  of  the 
atoms,  and,  consequently,  the  equilibrium  of  their  mutual  attraction ;  under  its 
action  they  are  then  deposited  in  the  directions  to  which  their  attraction  is  the 
strongest.  The  formation  of  new  products  rests  upon  the  establishment  of  a  new 
state  of  equilibrium,  and  they  suffer  no  further  change  as  long  as  they  continue 
exposed  to  the  same  degree  of  heat ;  but  if  the  temperature  be  raised,  a  new 
disturbance  occurs,  and,  consequently,  a  new  state  of  equilibrium,  and  a  new  mode 
of  arrangement  of  the  elements.  On  being  exposed  to  a  faint  red  heat,  acetic 
acid  is  decomposed  into  carbonic  acid  and  acetone  ;  the  carbonic  acid  contains 
two-thirds  of  the  oxygen,  while  the  acetone  contains  all  the  hydrogen  of  the  acetic 
acid  ;  at  a  higher  temperature  the  acetone  is  decomposed  into  a  compound  of 
carbon  which  contains  oxygen,  and  into  an  oleaginous  hydro-carburet.  Exposed 
to  a  temperature  of  392°  F.,  the  styrole  becomes  solid  and  hard,  loses  its  fluid 
character,  and  passes  into  a  form  resembling  the  most  beautiful  crystal  glass. 


INFLUENCE  OF  THE  CONDITION  OF  CHEMICAL  ACTIVITY. 

It  has  been  observed  that  platinum  does  not  decompose  nitric  acid,  and  that  it  is 
neither  oxidized  or  dissolved  by  this  acid.  A  compound  of  platinum  and  silver 
dissolves,  however,  easily  in  nitric  acid. 


INFLUENCE  OF  THE  CONDITION  OF  CHEMICAL  ACTIVITY  UPON  THE 
CAPACITY  OF  BODIES  TO  ENTER  INTO  COMBINATIONS. 

Metallic  copper  does  not  decompose  water,  when  boiled  with  sulphuric  acid  ; 
certain  compounds  of  zinc,  copper,  and  nickel  dissolve,  however,  easily  in  sul- 
phuric acid,  with  a  development  of  hydrogen.  In  certain  relations,  compounds 
of  these  three  metals  will  not  dissolve  in  sulphuric  acid,  but  if  a  trace  of  nirnc 
acid  be  present,  oxidation  begins,  which  is  then  continued  without  further  co-ope- 


20  CHEMISTRY  AND  PHYSICS  IN  RELATION 

ration  of  the  nitric  acid.  The  solution  of  the  platinum  and  copper  follows  in  both 
cases  against  the  electrical  laws  ;  heat  or  other  causes,  which  might  increase  the 
affinity,  have  no  share  in  the  process. 

INFLUENCE  OF  THE  SAME  CONDITION  UPON  THE  CAPACITY  OF 
BODIES  TO  SUFFER  DECOMPOSITION. 

If,  further,  binoxide  of  hydrogen  be  brought  into  contact  with  hyper-oxide  of 
lead  or  hyper-oxide  of  silver,  the  decomposition  of  the  former  is  accelerated,  as 
by  many  solid  bodies,  and  it  is  resolved,  with  effervescence,  into  oxygen  and 
water ;  but  the  molecules  of  both  metallic  oxides  undergo  a  like  decomposition 
when  in  contact  with  the  decomposing  parts  of  the  binoxide  of  hydrogen ;  oxide 
silver  is  resolved  into  oxygen  and  the  metal,  hyper-oxide  of  lead  into  oxygen  and 
oxide  of  lead.  Both  oxides  behave  as  if  they  had  been  exposed  to  a  faint  red 
heat. 

It  follows,  from  these  appearances,  that  the  condition  of  the  combination  or 
decomposition  of  a  body,  or  of  its  change  of  place  or  motion,  may  exercise  an 
influence  upon  the  molecules  of  many  other  combinations  brought  in  contact  with 
it ;  they  pass  into  the  same  condition  ;  their  elements  are  in  a  like  manner  sepa- 
rated, and  they  thus  gain  the  power,  which  they  did  not  possess  in  themselves,  of 
entering  into  a  combination. 

The  decomposition  of  the  second  body  naturally  proves  that  the  resistance  of  the 
force,  which  strives  to  hold  the  atoms  together  in  their  original  mode  of  arrange- 
ment, must  be  less  than  the  force  of  that  activity  which  affects  it. 


INFLUENCE  OF  A  SIMILAR  CONDITION  UPON  ORGANIC  SUBSTANCES. 

The  property  possessed  by  any  substance  in  combination  or  decomposition,  to 
call  forth  in  other  bodies  of  similar  or  dissimilar  nature  in  contact  with  it,  a  condi- 
tion of  form  and  character  like  its  own,  belongs,  in  a  much  higher  degree,  to 
organic  bodies  than  to  inorganic  substances. 


DECAYED  WOOD. 

Decayed  wood  brought  in  contact  with  that  which  is  sound,  changes  gradually 
the  sound  body,  under  similar  conditions,  to  a  state  of  decomposition. 


RELATION  OF  UREA  AND  HIPPURIC  ACID  IN  URINE. 

In  fresh  urine,  if  there  is  a  complete  exclusion  of  oxygen,  no  change  of  the 
urea,  or  of  the  hippuric  acid  contained  in  it  occur ;  or  exposure  to  the  air,  another 
substance,  occurring  in  urine  in  consequence  of  the  oxygen  being  taken  up,  suffers 
a  change  in  form  and  properties,  which  is  communicated  to  the  urea  and  the 
hippuric  acid.  Urea  is  decomposed  into  carbonic  acid  and  ammonia,  and  in  the 
place  of  the  hippuric  acid  which  disappears,  benzoic  acid  is  found. 

INFLUENCE  OF  THE  PUTREFACTION  OF  WOOD  ON  THE  OXIDATION 

OF  HYDROGEN. 

Decayed  wood  takes  up  oxygen  from  the  air,  and  gives  out  an  equal  volume  of 
carbonic  acid.  If  hydrogen  be  added  to  the  air,  it  becomes  oxidized  with  the 


TO  PHYSIOLOGY  AND  PATHOLOGY.  21 

wood,  and  acquires  the  property  of  combining,  at  the  ordinary  temperature,  with 
the  oxygen. 

Under  similar  circumstances  the  vapour  of  alcohol  absorbs  oxygen,  and  becomes 
changed  into  acetic  acid. 

THE  FIBRIN  OF  THE  BLOOD  AND  YEAST  ACT  SIMILARLY  TOWARDS 
BINOXIDE  OF  HYDROGEN. 

Fresh  fibrin  stands  in  the  same  relation  to  air  as  damp  wood,  passing  equally 
into  a  state  of  decomposition  ;  if,  in  this  condition,  it  be  decomposed  by  binoxide 
of  hydrogen,  the  latter  is  immediately  resolved  into  oxygen  and  hydrogen ;  but  if 
the  fibrin  be  heated  to  boiling,  this  accelerating  action  ceases  entirely.  Yeast 
behaves  in  a  like  manner,  occasioning  an  immediate  decomposition  of  the  con- 
stituents of  the  binoxide  of  hydrogen ;  but  if  it  be  previously  heated  to  boiling, 
the  action  ceases. — (Schlossberger.) 


RELATION  OF  COMBINED  ORGANIC  ATOMS  AMONGST  THEMSELVES. 

These  properties  are  in  the  highest  degree  appreciable  in  complex  organic 
atoms.  The  larger  the  number  of  individual  elements  and  atoms,  which  have 
associated  themselves  into  a  group  of  atoms  of  definite  properties,  and  the  more 
various  the  directions  of  their  attractions,  the  smaller  in  the  same  relation  must  the 
force  be  which  attracts  together  every  two  or  three  of  the  minutest  molecules  of 
the  group  ;  they  offer  a  slight  resistance  to  the  causes — whether  heat  or  chemical 
affinities — which  effect  a  change  in  their  form  and  properties  ;  and  are  as  easily 
changed  and  decomposed  as  other  substances  of  simple  combination. 


PUTREFACTION. 

The  constituents  of  plants  and  animals  into  which  sulphur  and  oxygen  enter  are 
formed  of  compound  organic  atoms ;  from  the  moment  they  are  separated  from  the 
body,  and  come  in  contact  with  the  air,  they  pass  into  a  state  of  decomposition, 
which,  once  begun,  continues  even  after  the  air  is  excluded.  The  colorless 
sections  of  a  potato,  turnip,  or  apple,  soon  become  discolored  and  brown  on 
exposure  to  the  air. 

In  all  these  substances,  the  presence  of  a  certain  quantity  of  water,  by  which 
the  minutest  parts  receive  mobility,  is  a  necessary  requirement,  in  order  that  on  a 
transient  contact  with  the  air  a  change  of  form  and  properties,  and  a  breaking  up 
into  new  products  may  be  called  forth  ;  both  of  which  continue  until  not  a  particle 
of  the  original  body  remains.  .  This  process  has  been  familiarly  designated  by  the 
term  putrefaction. 


AFFINITY  NOT  THE  CAUSE  OF  PUTREFACTION. 

Experience  teaches  us  further,  that  a  number  of  substances  brought  in  contact 
with  these  putrefying  sulphurous  and  oxygenous  matters,  when  in  the  act  of 
putrefaction,  in  like  manner  change  their  properties ;  in  the  act  of  decomposing, 
their  elements,  group  themselves  into  new  products,  in  the  composition  of  which 
there  are,  in  most  cases,  none  of  the  elements  of  the  putrefying  substances  taken 
up.  From  all  these  phenomena  it  is  clear  that  the  decomposition  of  the  second 
body  is  not  effected  in  consequence  of  an  indication  of  affinity,  since  the  idea  of 
affinity  is  inseparable  from  the  idea  of  combination. 


22  CHEMISTRY  AND  PHYSICS  IN  RELATION 


DECOMPOSITION  OF  AMYGDALIN  AND  ASPARAGIN  BY  PUTREFYING 

SUBSTANCES, 

In  contact  with  the  nitrogenous  constitutent  of  germinating  barley  (diastase) 
asparagin  is  resolved  into  succinic  acid  and  ammonia ;  amygdalin  resolves  itself 
with  the  nitrogenous  constituent  of  sweet  almonds  (emulsine)  into  prussic  acid,  oil 
of  bitter  almonds  and  sugar ;  salicin  into  saligenin  and  sugar. 


THE  CONVERSION  OF  STARCH  INTO  SUGAR. 

Potatoes  and  the  flour  of  the  cereal  grasses  contain  no  sugar.  The  mere  contact 
with  water  is  sufficient,  in  consequence  of  the  change  that  is  thence  effected  in  the 
sulphurous  and  nitrogenous  constitutents,  to  bring  about  a  conversion  of  the  starch 
into  sugar. 


THE  SAME  EFFECT  PRODUCED  BY  ANIMAL  MEMBRANE. 

Animal  membrane,  when  moistened  with  water,  causes  sugar  of  milk  and  grape 
sugar  to  pass  into  lactic  acid  ;  a  similar  property  is  possessed  by  the  gluten  of  the 
cereal  grasses,  by  animal  casein,  and  by  diastase. 

FERMENTATION  AND  ITS  PROPERTIES. 

The  property  of  an  organic  body  to  pass  into  the  same  state  of  putrefying 
decomposition  as  the  body  with  which  it  is  brought  in  contact,  is  termed  the 
process  of  fermentation. 

DIFFERENT  DEGREES  OF  PUTREFACTION,  AND  THEIR  INFLUENCE 
UPON  FERMENTATION. 

If  it  be  true  that  the  change  of  form  and  property  in  the  fermenting  body 
be  dependent  upon  those  which  are  effected  in  the  putrefying  body,  or  in 
the  agent  of  fermentation :  if  the  new  order  of  deposition  of  the  atoms  of  the 
one  body,  be  influenced  by  the  direction  in  which  the  parts  of  the  other  arrange 
themselves ;  if  finally,  the  fermenting  body  behave  as  if  it  were  a  part  or 
constituent  of  the  agent  of  fermentation,  it  is  clear  that  the  mode  of  separation  in 
the  one  must  change  with  that  of  the  other  body  ;  the  fermenting  body  must  yield 
other  products  if  the  disunion,  or  the  chemical  condition  of  motion  change  the 
agent  of  fermentation.  Innumerable  experiments  testify  to  the  correctness  of 
these  conclusions. 


MILK  OF  ALMONDS  AND  SUGAR. 

When  the  milk  of  almonds,  which  in  its  fresh  state  exercises  no  influence  upon 
sugar,  is  left  for  a  short  period  of  time,  it  ceases  to  act  upon  amygdalin  :  and  if  in 
this  condition  sugar  be  added,  the  latter  begins  to  ferment,  and  separates  into 
alcohol  and  carbonic  acid.  If  the  almond  milk  be  left  still  longer,  it  converts  the 
sugar  into  lactic  acid.  A  similar  property  is  possessed  by  diastase,  which,  when 
fresh,  converts  starch  into  sugar ;  but  after  a  period  of  eight  days,  it  loses  this 
action,  and  gives  to  fermentation. 


TO  PHYSIOLOGY  AND  PATHOLOGY.  23 


CASEIN  AND  SUGAR. 

In  the  first  period  of  its  putrefaction  the  casein  of  milk  converts  the  sugar  of 
milk  and  the  grape  sugar  into  lactic  acid  ;  at  a  higher  temperature  the  sugar  of 
grapes  passes  into  alcohol  and  carbonic  acid  ;  and  if  the  formation  of  free  acids  be 
hindered  by  the  addition  of  an  alkaline  base,  the  casein  in  the  last  stage  of  its 
metamorphosis,  occasions  a  decomposition  of  the  saccharine  atoms  into  carbonic 
acid,  butryic  acid  and  hydrogen. 


ANIMAL  MEMBRANE  AND  SUGAR. 

Animal  membrane  behaves  in  the  same  manner.  At  first  it  effects  a  change  of 
the  starch  into  sugar,  then  of  the  sugar  into  lactic  acid,  and  subsequently  of  the 
sugar  into  carbonic  acid  and  alcohol. 

THE  INFLUENCE  OF  A  HIGHER  TEMPERATURE  UPON 
FERMENTATION. 

The  same  sugar  of  beet  root,  which  ferments  at  an  ordinary  temperature,  and  is 
decomposed  into  alcohol  and  carbonic  acid,  yields,  on  raising  the  temperature  of 
the  juice  without  the  addition  of  any  foreign  substance,  mannite,  lactic  acid,  gum, 
carbonic  acid  and  hydrogen. 


FOUSEL  OIL  FROM  SUGAR. 

The  same  sugar  yields,  on  changing  again  the  conditions  of  its  fermentation, 
butyric  acid ;  it  is  decomposed,  in  the  fermenting  molasses  of  beet-root  sugar  into 
water,  carbonic  acid  and  hydrated  oxide  of  amyle  (fousel  oil.) 

SEPARATION  OF  THE  SUGAR,  SIMILAR  TO  THAT  OF  ACETIC  ACID 
OCCASIONED  BY  THE  ACTION  OF  HEAT. 

Milk  sugar  and  sugar  of  grapes  contain  the  same  elements  as  lactic  acid,  and 
combined  in  the  same  relative  proportions. 

The  products  which  appear  on  the  fermentation  of  sugar  of  grapes  contain 
precisely  the  same  elements  as  an  atom  of  sugar.  Its  decomposition  is  a  simple 
separation,  or  transposition  of  its  atoms,  as  is  seen  in  acetic  acid  on  the  application 
of  a  higher  degree  of  temperature.  The  carbonic  acid  contains  two-thirds  of  the 
oxygen :  the  alcohol  all  the  hydrogen  of  the  atom  of  sugar. 

THE  PROPERTY  OF  CAUSING  FERMENTATION  IS  COMMON  TO  ALL 
COMPOUND  ORGANIC  ATOMS. 

If  we  take  into  consideration  that  the  capacity  of  producing  putrefaction  or 
fermentation  is  common  to  bodies  of  the  most  various  forms  of  composition  ;  that 
blood,  meat,  cheese,  membranes,  cells,  saliva,  diastase,  milk  of  almonds,  &c.,  gain 
this  property  as  soon  as,  by  the  chemical  action  of  oxygen,  a  disturbance  of  the 
state  of  equilibrium  has  been  excited  in  the  attraction  of  their  elements,  it  would 
seem  that  all  doubt  of  the  true  cause,  by  which  these  phenomena  are  brought 
about,  must  vanish. 


24  CHEMISTRY  AND  PHYSICS  IN  RELATION 


CAUSES  OF  THE  CHANGE  OF  FORM  AND  PROPERTY  OF  MATTER. 

A  change  of  place  or  position  in  the  most  minute  particles  of  a  number  of 
compound  substances,  and  their  decomposition,  or  conversion  into  new  products 
may  be  called  forth  by  chemical  action,  by  heat,  or  electricity  ;  and  it  may  also 
be  occasioned  by  a  transference  of  some  condition  of  motion,  or  by  contact  with  a 
body,  the  particles  of  which  are  undergoing  a  change  of  place. 


CONTINUANCE  OF  THE  DECOMPOSITION. 

If,  from  any  external  cause — by  contact  with  oxygen,  &c. — the  condition  of 
equilibrum  in  the  attractive  force  of  the  elements  of  one  of  these  compound  atoms 
be  disturbed,  the  result  is  the  establishment  of  a  new  condition  of  equilibrium. 
The  motion  imparted  to  the  first  molecule  is  transferred  to  the  second,  the  third, 
&c.,  of  the  parts  of  similar  nature,  extending  even  to  all  dissimilar  particles,  and 
to  all  other  substances,  if  the  force  which  held  together  their  elements  in  their 
original  form  and  character  be  less  than  that  acting  upon  them  with  an  opposite 
tendency.  Want  of  power  to  maintain  an  original  condition  is  want  of  power  of 
resistance.  Every  body  which  is  capable  of  offering  this  degree  of  resistance, 
hinders  putrefaction  and  fermentation  in  most  cases  by  entering  into  a  chemical 
combination  with  the  body  susceptible  of  either  of  these  conditions  ;  and  the  power 
of  maintaining  the  original  mode  of  arrangement  is  strengthened  by  every  new 
accession  of  the  force  of  attraction.  To  the  force  which  maintains  the  condition 
of  the  first  body,  is  added  a  second  attraction  which  must  be  overcome  before  the 
elements  of  the  first  can  change  their  locality  or  size. 


ANTISEPTIC  SUBSTANCES. 

Amongst  the  substances  which  counteract  putrefaction  and  fermentation  we  must 
mention  before  others,  sulphurous  and  arsenious  acids ;  further,  many  mineral 
acids,  metallic  salts,  empyreumatic  substances,  volatile  oils,  alcohol,  and  common 
salt. 

These  substances  exercise  a  very  unequal  influence  upon  putrid  matter.  Alcohol 
and  common  salt  in  certain  quantities  arrest  putrefaction,  and  consequently  the 
process  of  fermentation,  by  removing  from  the  putrid  body  a  certain  quantity  of 
water,  which  is  a  necessary  requirement  for  this  change,  Sulphurous  acid,  which 
is  capable  of  entering  into  combination  with  all  organic  matters  generally,  and 
therefore,  with  all  bodies  susceptible  of  putrefaction,  hinders  this  process  on  the 
same  principles. 


RELATION  OF  ARSENIOUS  ACID  TO  MEMBRANES. 

Arsenious  acid  does  not  exert  the  smallest  influence  upon  the  fermentation  of 
sugar  in  the  juices  of  plants,  or  upon  the  action  of  yeast  on  sugar: — (Schloss- 
berger.)  Neither  does  it  affect  the  putrefaction  of  the  blood,  but  its  action  on 
membranes  and  the  membranous  structures  is  unquestionable.  Whilst  a  bladder, 
or  a  bit  of  membrane  covered  with  water  is  thoroughly  decomposed  and  liquefied, 
giving  off,  in  the  course  of  six  weeks  or  less,  a  most  offensive  stench,  another 
piece  of  membrane  or  bladder  likewise  in  contact  with  water  will  remain  un- 
changed and  without  smell,  if  arsenious  acid  have  been  added  to  the  fluid  ;  the 
explanation  of  this  difference  is,  that  the  gelatinous  tissue  enters  into  combination 
with  the  arsenious  acid  in  the  same  manner  as  skin  combines  with  tannic  acid. 


TO  PHYSIOLOGY  AND  PATHOLOGY. 


By  means  of  a  knowledge  of  the  causes  of  the  origin  and  extension  of  putre- 
faction in  organic  atoms,  we  are  able  to  give  a  simple  reply  to  the  question  of 
the  nature  of  many  forms  of  contagion  and  miasma,  as  the  following  remarks 
will  show. 


EXTENSION  OF  THE  PROCESSES  OF  PUTREFACTION  AND  FERMEN- 
TATION IN  THE  LIVING  ANIMAL  BODY. 

It  still  remains  a  question  with  many,  whether  there  are  facts  to  prove  that  the    / 
condition  of  decomposition  or  putrefaction  of  a  substance  be  propagated  to  parts/-- 
or  constituents  of  the  living  body,  and  whether  by  contact  with   the  putrefying 
substance,  a  condition  will  be  induced  in  the  parts  of  the  human  body,  similar  to"~^ 
that  at  work  in  the  molecules  of  the  putrid  matter.     We  think  there  can  be  no 
hesitation  in  answering  this  inquiry  in  the  affirmative. 

\:-:^V.  i*7  ^ 

FACTS. 

It  is  a  fact  that  the  dead  body  often  passes  into  such  a  state  of  decomposition 
while  in  the  anatomical  theatre  that  the  blood  of  the  living  body  is  affected  by 
it ;  the  slightest  puncture  with  a  knife  that  has  been  used  in  dissection  induces  a 
dangerous  or  even  fatal  termination.  The  facts  observed  by  Magendie  that  vomit- 
ing, lassitude,  and  even,  after  a  prolonged  period,  death  has  been  induced,  by 
applying  blood  that  is  in  a  state  of  putrefaction,  cerebral  substance,  bile,  and 
putrefying  pus  to  fresh  wounds,  have  never  yet  been  contradicted. 

It  is  a  fact  that  the  use  of  many  articles  of  food,  as  ham,  sausages,  &c.,  in 
certain  stages  of  their  decomposition,  induce  the  most  dangerous  conditions  of 
disease  in  the  healthy  body,  and  not  unfrequently  are  the  cause  of  death. 

WHAT  IS  TO  BE  UNDERSTOOD  BY  THE  TERM  "PRODUCTS  OF 

DISEASE." 

These  facts  prove  that  an  animal  substance  in  the  act  of  decomposition  may 
induce  a  process  of  disease  in  the  bodies  of  healthy  individuals,  and  that  this 
condition  can  be  transferred  to  their  organs  and  constituent  parts.  But  as  the 
products  of  disease  can  be  only  understood  to  mean  parts  and  conditions  of  the 
living  body  in  a  condition  of  change  in  their  form  and  properties,  it  is  clear  that 
as  long  as  this  condition  remains  imperfect,  disease  may  be  transferred  to  a  second, 
or  third  individual,  &c. 

ANTISEPTIC  SUBSTANCES  RETARD  THE  EXTENSION  OF  CONTAGION 

AND  MIASMA. 

If  now  we  take  into  consideration,  further,  that  all  those  substances  or  causes 
which  destroy  the  propagating  tendency  of  contagion  and  miasma,  are  at  the  same 
time  requirements  for  the  removal  of  all  processes  of  putrefaction  and  fermenta- 
tion— if  daily  experience  show  that,  empyreumatic  substances,  as  pyroligneous 
acid  for  instance,  which  most  strongly  counteract  decomposition,  are  the  means  of 
changing  entirely  the  process  of  disease  in  wounds  suppurating  unhealthily,  and 
if  further  free  or  combined  ammonia  (the  almost  invariable  product  of  putrefactive 
processes)  be  found  during  many  contagious  diseases,  as  for  instance,  typhus  in  the 
surrounding  atmosphere,  and  in  the  urine  and  faeces ;  it  surely  then  seems 


26  CHEMISTRY  AND  PHYSICS  IN  RELATION 

impossible  to  entertain  a  doubt  concerning  the  cause  of  the  origin  and  further  pro- 
pagation of  a  number  of  contagious  diseases. 


PUTREFACTION  PROCESSES  AS  CAUSES  OF  CONTAGIOUS  DISEASES. 

General  experience  has  at  length  shown  us  that  "  the  origin  of  epidemic  diseases 
can  often  be  traced  to  the  putrefaction  of  a  number  of  animal  and  vegetable  substances; 
that  miasmatic  diseases  become  epidemic  where  there  is  constant  decomposition 
of  organic  matter  in  marshy,  damp  districts.  And  that  they  also  develope  them- 
selves epidemically  under  similar  circumstances  after  inundations ;  besides,  in  other 
places  where  a  large  number  of  people  are  assembled  together  with  little  change 
of  air — as  in  ships,  prisons,  and  besieged  places,  &c.  ;*  further  on,  at  page  27,  the 
same  author  observes  that  "  we  can  never  prognosticate  the  origin  of  epidemic 
disease  with  more  certainty,  than  when  a  marshy  flat  has  been  dried  up  by  con- 
tinued heat,  or  when  excessive  heat  follows  extensive  inundation." 


CONCLUSIONS. 

Here  our  deduction  is  fully  justified  according  to  the  rule  of  natural  inquiry, 
that  in  all  cases  where  a  process  of  putrefaction  has  preceded  the  first  indications 
of  disease,  or  where  disease  can  be  communicated  by  solid,  fluid,  or  gaseous  pro- 
ducts, and  where  no  more  immediate  cause  can  be  adduced,  the  substances  or 
matter  in  the  act  of  decomposition  must  be  looked  upon  as  the  most  probable 
cause  of  disease. 


POWER  OF  INFECTION— IN  WHAT  IT  CONSISTS. 

The  requirement  for  the  capacity  of  infecting  a  second  individual,  is  the  pre- 
sence in  the  body  of  the  latter  of  a  substance  which  can  oppose  no  resistance 
either  in  itself,  or  through  the  vital  energy  in  the  organism  to  the  causes  affecting 
a  change  of  form  and  property.  If  this  substance  were  a  necessary  constituent  of 
the  body,  disease  must  be  transferable  to  all  individuals  ;  if  only  an  accidental 
constituent,  those  persons  alone  would  be  infected  in  whom  this  substance  was 
present  in  sufficient  quantity,  and  of  the  characteristic  nature.  The  termination 
of  disease  is  only  a  destruction  and  removal  of  this  matter  ;  it  is  a  re-establishment 
of  the  condition  of  equilibrium  of  those  causes  in  the  organism  which  regulate  its 
normal  functions,  and  which  had  been  temporarily  suspended. 


A  CHALLENGE  TO  INVESTIGATION. 

Practical  medicine  will  soon  decide  whether  this  view  be  correct  or  not;  and  it 
will  then  be  shown  whether  there  is  any  actual  connection  between  the  relation  of 
arsenious  acid  to  animal  membranes  out  of  the  body,  and  their  action  in  certain 
fevers ;  and  between  the  relation  of  mercurial  compounds  to  animal  substances, 
and  their  action  in  contagious  diseases. 

If  this  so-called  chemical  view  do  not  serve  as  a  guide  and  director  to  the  phy- 
sician, after  a  careful  study  of  the  processes  of  putrefaction  of  simple  and  com- 
pound bodies,  and  of  the  materials  and  causes  by  which  these  processes  are 
altered,  hindered,  or  accelerated ;  and  if  a  comparison  of  this  with  other  analo- 
gous processes  in  the  human  organism,  be  not  the  means  of  enlarging  his  views 

*IEenle,  Untersuchungen,  p.  52. 


TO  PHYSIOLOGY  AND  PATHOLOGY.  27 

upon  disease,  and  raising  to  a  more  scientific  basis  his  knowledge  of  the  remedial 
agents  to  be  employed  ;  then,  indeed,  it  were  of  no  avail  to  endeavor  to  support 
this  theory.  Its  simplicity  has  stood  much  in  the  way  of  its  being  generally 
received  ;  for  at  the  very  time  that  every  physician  or  physiologist  does  not  hesi- 
tate to  ascribe  the  most  striking  changes  in  vital  processes  to  bad  nutriment,  want 
of  fresh  air,  or  the  continuous  use  of  salted  food,  &c. — while  no  one  feels  any 
scruple  in  assigning  a  scarcely  appreciable  difference  of  temperature  as  the  cause 
of  inflammation,  fever,  and  death — one  of  the  most  important  causes  of  a  change 
of  form  and  properties  is  disregarded,  as  exercising  no  influence  upon  the  organic 
vital  process. 

Here  is  a  theory  strengthened  by  a  firmly  linked  chain  of  numerous  and  most 
evident  facts,  to  which  a  critical  investigation  is  denied,  although  there  is  nothing: 
that  can  be  advanced  against  it  save  its  comprehensibility.  But  it  is  precisely  on 
this  latter  character  that  the  difference  rests,  which  is  observed  in  the  result  of 
various  methods  of  physical  investigation.  Although  every  pathologist  and  phy- 
siologist is  fully  convinced  that  no  organic  process  can  be  explained  without  the 
co-operation  of  chemical  and  physical  forces,  every  theory  which  has  hitherto 
been  based  upon  such  causes  has  been  invariably  doubted  and  rejected. 

If  we  compare  the  so-called  chemical  theory  with  the  principles  of  the  parasite 
theory,  we  cannot  comprehend  how  intellectual  men,  and  the  most  practised 
observers,  can  defend  and  lend  their  sanction  to  views  which  the  experience  of  each 
succeeding  day  must  refute. 


THE  PARASITE  THEORY. 

The  principles  of  the  parasite  theory  may  be  referred  to  two  facts,  viz.,  to  the 
propagation  of  the  itch,  and  to  a  disease  appearing  in  silk  worms  called 
muscardine. 


THE  ITCH. 

The  itch  is  an  inflammation  of  the  skin,  occasioned  by  the  irritation  of  a  kind  of 
mite  (acaru-s  scabiei,  sarcoptes  humanus,*)  which  lives  upon  the  skin,  or,  more 
correctly  speaking,  burrows  within  it.  For  the  communication  of  the  itch  con- 
tinous  vicinity  is  necessary,  and  that  especially  at  night,  as  the  itch  mite  is  a 
nocturnal  depredator.  The  fact  of  the  itch  mite  being  the  vehicle  of  the  conta- 
gious character  of  the  itch,  is  proved  by  the  following  facts :  inoculation  with  the 
pus  of  itch  pustule-s  does  not  engender  the  itch,  any  more  than  the  application  of 
the  crusts  of  scabious  pustules  upon  the  arm.  Secondly,  the  disease  is  healed  by 
rubbing  off  the  mites  with  brick  dust;  and  it  can  only  be  propagated  by  the 
impregnated  female  animalcule.  The  itch  may  continue  until  it  induces  general 
permanent  disease,  which  in  these  cases  becomes  established,  and  cannot  be 
spontaneously  cured. 


THE  ITCH  A  CONTAGIOUS  DISEASE  PROPAGATED  BY  AN  ANIMAL. 

Contagion  of  the  itch  is,  according  to  this  theory,  an  animal  with  a  mandibular 
apparatus,  which  lays  eggs ;  we  term  it  fixed  contagion,  because  it  cannot  fly,  and 
its  eggs  cannot  be  transported  by  atmospheric  influence. 

If  it  be  proved  that  the  itch  may  be  propagated  by  animals,  it  requires  neither  a 

*  An  excellent  account  of  this  insect,  and  of  the  other  parasites  infesting  the  human 
body  is  given  in  VogePs  Pathological  Anatomy.  See  Dr.  Day's  translation,  p.  419. 


28  CHEMISTRY  AND  PHYSICS  IN  RELATION 

chemical  nor  any  other  theory  to  explain  the  communication  of  the  disease  ;  and 
it  becomes  evident  that  all  conditions  which  are  similar  to  the  itch  belong  to  this 
class,  where  observation  shows  approximating  or  like  causes,  for  the  communioa-' 
tion  and  extension  of  the  disease. 


CONTAGIOUS  DISEASES  NOT  COMMUNICATED  BY  ANIMALCULES. 

If  now  it  be  asked,  what  results  have  been  obtained  from  investigation  into 
these  and  other  similar  causes  of  infectious  diseases,  we  may  answer  that  in  the 
contagion  of  small  pox,  the  plague,  syphilis,  scarlatina,  measles,  typhus,  yellow 
fever,  dysentery,  hydrophobia,  &c.,  the  most  attentive  observations  have  not  been 
able  to  trace  any  animalcules  or  organic  entities  to  which  the  means  of  propagating 
the  disease  could  be  ascribed. 


PARASITES  IN  BODIES  OF  THE  HIGHER  CLASSES  OF  ANIMALS, 

We  have  already  observed,  that  there  are  a  number  of  insects  which  can  alone 
be  developed  and  propagated  in  the  body  or  under  the  skin  of  the  higher  animals, 
and  that  they  may,  in  many  cases,  induce  disease,  and  even  death  ;  and  it  will, 
therefore,  be  perfectly  clear  that  the  itch  mite  belongs  to  this  class  of  diseases, 
since  the  size  of  the  animalcule  can  make  no  difference  in  the  explanation. 

There  are,  accordingly  diseases  occasioned  by  animalcules,  parasites,  which 
develope  themselves  in  the  bodies  of  other  animals,  and  thrive  at  the  cost  of  some 
of  their  constituent  parts ;  and  they  cannot  be  mistaken  for  other  diseases,  where 
such  causes  do  not  prevail,  whatever  resemblances  there  may  be  in  external 
indications.  It  is  possible  that  further  observations  may  attest  the  fact,  that  some 
or  other  of  the  contagious  diseases  belong  to  the  class  dependent  upon  parasites  ; 
until,  however,  such  a  fact  be  established,  we  must,  according  to  the  rules  of 
natural  investigation,  avoid  assuming  it.  It  is  the  province  of  scientific  inquiry  tc 
discover  the  especial  causes  by  which  they  have  been  induced,  the  simple 
question  concerning  which  will  lead  the  way  to  an  explanation  of  the  subject. 

That  infection  in  contagious  diseases  is  dependent  upon  an  organic  being,  and 
that  the  itch  must  be  regarded  as  a  type  of  contagious  diseases,  were  facts  which 
it  was  endeavored  to  ground  upon  the  deduction  of  like  effects  springing  from  like 
causes.*  A  similar  mode  of  reasoning  has,  for  centuries,  impeded  the  advance 
of  the  natural  sciences,  and  even  continues  at  the  present  day  to  lead  to  man}' 
errors. 

The  pure  miasmatic  diseases,  and  their  so-called  miasma,  have  not  as  yet  been 
laid  open  to  investigation  in  reference  to  their  origin  and  the  manner  of  their 
extension,  and  on  that  account  no  explanation  has  hitherto  been  attempted,  either 
by  a  chemical  or  parasite  theory.  The  parasite  theory  has  designated  muscardine 
as  the  type  of  those  miasmatic  contagious  diseases  which  arise  from  matter  derived 
either  from  the  air  or  from  the  diseased  body. 


MUSCARDINE. 

Muscardine  is  a  disease  of  the  silk  worm,  occasioned  by  a  fungus.  The  germ 
of  the  fungus,  when  introduced  into  the  body  of  the  worm,  grows  in  eating  its  way 
into  the  interior,  and  after  the  death  of  the  animal  it  penetrates  the  skin,  when  the 
surface  soon  appears  covered  with  a  forest  of  fungi,  which  by  degrees  dry  up,  and 
are  converted  into  dust :  this  is  raised  and  scattered  in  the  air  by  the  slightest 

*Hen&,  Zeitschrift,  2  Bd.  p.  305. 


TO  PHYSIOLOGY  AND  PATHOLOGY.  29 

motion  of  the  body  on  which  the  fungus  grows.  Good  nutrition,  and  perfect 
health  and  strength  increase  the  capacity  for  infection ;  and  thus,  in  a  colony  of 
silk  worms,  the  finest  and  largest  are  always  the  most  affected  by  the  disease. 


[PARASITES  IN  ANIMALS  AND  PIANTS. 

Similar  parasites  have  been  observed  on  diseased  fish,  in  infusoria,  and  in  hen's 
eggs ;  and  it  is  clear  that  these  observations  confirm  a  series  of  facts  regarding  the 
animal  organism  which  often  occur  in  the  vegetable  world,  proving  that  disease  and 
death  are  frequently  induced  by  parasites,  which  live  exclusively  upon  the  constit- 
uent parts  of  other  bodies ;  as  yet,  however,  no  connection  has  been  drawn 
between  these  facts  and  the  origin  and  propagation  of  miasmatic  contagious  diseases  ; 
and  if  it  be  allowable  to  designate  a  fungus,  or  its  spores,  by  the  term  contagion,  it 
is  clear — since  the  size  of  the  fungus  makes  no  difference  in  our  mode  of  consi- 
dering it — that  some  sources  of  contagion  attain  to  a  length  of  six  or  eight  inches, 
this  being  the  size  of  the  fungus,  Sphceria  Roberta,  which  developes  itself  in  the 
body  of  the  New  Zealand  grub,  and  occasions  its  death. 

FALSE  VIEWS  OF  THE  CAUSES  OF  PUTREFACTION  ARE  THE 
FOUNDATION  OF  THE  PARASITE  THEORY. 

A  view  of  the  cause  of  fermentation  and  putrefaction,  which  is  thoroughly  false 
in  its  principles,  has  hitherto  served  as  the  main  support  of  the  parasite  theory. 
Its  adherents  regard  putrefaction  as  a  decomposition  of  organic  beings,  by  infusoria 
and  fungi,  and  every  putrefying  body  as  a  sort  of  rampart  of  infusoria,  or  a 
plantation  of  fungi ;  and  thus,  according  to  this  view,  wherever  organic  bodies 
pass  into  putrefaction  to  any  extent,  the  whole  atmosphere  must  be  filled  with  the 
germs  of  contagion,  and  become  the  cause  of  disease. 


FUNGI  AND  INFUSORIA  DO  NOT  OCCASION  PUTREFACTION. 

It  has  not  escaped  the  advocates  of  the  parasite  theory,  that  a  close  connection 
exists  between  putrefaction,  contagion,  and  miasma ;  although  they  avoid  entering 
upon  an  explanation  of  the  mode  of  comprehending  the  connection  of  these 
phenomena,  and  their  mutual  dependence  upon  each  other.  This  connection  would 
be  established,  if  it  were  proved  that  infusoria  or  fungi,  induced  putrefaction  or 
fermentation  ;  that  by  them  and  their  process  of  digestion  and  respiration,  sugar  is 
resolved  into  equal  volumes  of  carbonic  acid  gas,  and  vapour  of  alcohol ;  and  that 
the  following  conversions  are  brought  about,  viz.,  urea  into  carbonate  of  ammonia ; 
salicin  into  sugar  and  saligenin ;  sulphate  of  protoxide  of  iron  into  sulphuret  of 
calcium  ;  sulphate  of  soda  into  sulphuret  of  sodium  ;  blue  indigo  into  white  indigo ; 
starch  into  sugar ;  sugur  into  lactic  acid ;  amygdalin  into  prussic  acid,  bitter  oil  of 
almonds,  and  sugar. 

The  following  remarks  will  show  how  thoroughly  untenable  are  these  views. 


OPPOSITION  BETWEEN  PUTREFACTION  AND  THE  PROCESS  OF  LIFE. 

The  constituents  of  \egetable  and  animal  structures  have  arisen  under  the 
dominion  of  nn  active  muse  of  change  in  the  form  and  properties  of  organisms; 
and  this  is  vital  force,  which  decides  the  direction  of  attraction,  and  opposes  the 
force  of  cohesion,  heat,  ;md  electricity,  destroying  the  influence  of  every  cause 
that  hinders  the  association  of  atoms  in  combinations  of  a  higher  order  without  the 


30  CHEMISTRY  AND  PHYSICS  IN  RELATION 

organism.  In  compositions  ot  such  various  nature  as  the  organic  atoms,  these 
other  forces  occasion  a  change  of  form  and  condition,  when  the  vital  force  after 
death  no  longer  opposes  their  action.  The  same  leaf,  or  the  same  grape  which 
possessed  the  capacity  of  giving  off  pure  oxygen  to  the  atmosphere,  submits  to 
the  chemical  action  of  the  oxygen  from  the  moment  of  its  separation  from  the  or- 
ganism, and  its  being  brought  in  contact  with  the  air. 

\        No  organism — no  portion  of  an  animal  or  plant  is  capable,  jifter  the  extinction 
1  of  vital  enprfly^  of  resisting  the  chemical  action  which  air  and  humidity  exercise 
I  upon  it,  and  its  elements  fall  back  under  the  unlimited  dominion  of  chemical  force. 
^Fermentation  and  putrefaction  are  the  stages  01  its  retrograde  development,  present- 
ing less  perfect  combination,  until  at  length  the  organic  atoms,  in  consequence  of 
continuously   acting  unorganic   forces,  return  to  their  simple    original  forms,  in 
which  they  may  serve  for  the  development  and  nutriment  of  new  generations. 


FUNGI  AND  INFUSORIA  ARE  SUBJECTED  TO  PUTREFACTION, 
FERMENTATION  AND  DESTRUCTION, 

Fungi  and  infusoria  are  organic  beings  with  constituent  parts  of  the  same  com- 
posite nature  as  those  of  the  higher  orders  of  vegetables  and  animals,  and  we 
observe  the  same  phenomena  in  their  bodies  after  death,  as  those  which  ac- 
company the  disappearance  of  all  organisms,  and  find  them  in  a  state  of  putrefac- 
tion, fermentation,  and  corruption ;  how  then  is  it  possible  to  regard  fungi  and 
infusoria  as  the  causes  of  these  processes,  when  they  themselves  become  putrid, 
fermented,  and  corrupt,  leaving  nothing  but  their  inorganic  skeletons? 


FUNGI  AND  INFUSORIA  ARE  THE  ATTENDANTS,  BUT  NOT  THE 
ORIGINATORS  OF  THE  PROCESS  OF  PUTREFACTION. 

No  one  will  deny  that  fungi  and  infusoria  are  found  in  a  great  number  of  putre- 
fying and  corrupting  substances ;  but  the  frequency  of  their  appearance  cannot 
possibly  be  adduced  as  a  motive  for  regarding  them  as  the  causes,  instead  of  the 
attendants  of  these  conditions.  Fungi  and  infusoria  are  shown  by  nature,  in 
reference  to  their  nutriment  and  development,  to  be  organic  atoms,  which  have 
ceased  to  be  parts  or  constituents  of  living  organisms,  and,  in  most  cases,  they  do 
not  appear  until  putrefaction  be  established,  or  is  complete,  and  the  process  of 
corruption  has  begun.  It  cannot  be  doubted  that  all  processes  and  their  respective 
products  are  changed  by  their  presence,  for  by  means  of  their  process  of  nutriment 
and  respiration,  they  accelerate  solution,  limiting  its  baneful  influence  upon  the 
surrounding  parts  to  the  shortest  possible  period  of  time. 


FUNGI  AND  INFUSORIA  HASTEN  THE  PROCESS  OF  PUTREFACTION 

AND  CORRUPTION. 

If  the  process  of  putrefaction  be  terminated  by  the  return  of  the  elements  of 
organic  beings  into  carbonic  acid,  and  carbonate  of  ammonia,  it  is  clear  that  the 
period  necessary  to  effect  this  conversion  must  be  most  perceptibly  curtailed  if  the 
putrefying  agent  be  a  plantation  of  infusoria,  millions  of  whom  are  busily  engaged 
in  leading  the  constituent  parts  of  the  body  into  a  state  of  decomposition  by  means 
of  their  respiratory  and  digestive  processes. 


TO  PHYSIOLOGY  AND  PATHOLOGY.  31 


BY  THIS  MEANS  THEY  BECOME  THE  ENEMIES  OF  THE  PROCESS 

OF  PUTREFATION. 

It  can  no  longer  be  doubted  tbat  nature  has  assigned  to  the  infusoria  the  im- 
portant part  of  being  the  enemies  and  opponents  of  all  contagion  and  miasma ; 
since  the  most  incontrovertible  facts  have  shown  that  the  green  and  red  infusoria 
are  during  their  life,  and  the  process  of  their  propagation,  sources  of  the  purest 
oxygen. 

In  a  similar  manner  fungi  check  putrefaction  by  converting  to  their  own  nutri- 
ment, the  sulphurous  and  nitrogenous  constituents  of  vegetables — the  actual 
originators  of  corruption;  and  thus-  further,  the  general  transition  into  the  final 
products  of  corruption. 


THE  NATURE  OF  YEAST. 

The  views  which  the  adherents  of  the  parasite  theory  have  formed  as  to  the 
cause  of  putrefaction,  mainly  rest  upon  observations  which  have  been  made  upon 
the  formation  of  the  yeast  in  the  fermentation  of  wine  and  beer ;  but  the  investi- 
gations into  the  nature  of  the  yeast  are  not  yet  closed,  and  it  is  to  be  presumed 
that  the  mocroscopic  observations  already  made  will  be  strengthened  by  further 
inquiry,  and  every  doubt  concerning  its  vegetable  nature  be  thus  set  aside ;  yet 
even  in  this  case  the  explanation  regarding  the  separation  of  sugar  into  alcohol  and 
carbonic  acid,  would  admit  of  no  other  expression  than  that  assumed  by  the 
chemical  theory. 

RELATION  OF  THE  YEAST  IN  SOLUTIONS  OF  SUGAR,  IN  GRAPE 
JUICE,  AND  BEER  WORT. 

It  is  a  perfectly  well  known  fact  that  in  spirituous  fermentation,  the  elements  of 
the  sugar  of  grapes  without  any  loss  of  weight,  and  those  of  the  sugar  of  cane 
with  an  increase  of  weight,  are  given  back  in  the  form  of  carbonic  acid  and 
alcohol.  We  cannot  here,  according  to  our  usual  conceptions,  speak  of  the  con- 
version of  the  atoms  of  sugar  to  the  nutritive  and  respiratory  processes  of  an 
organic  being.  The  weight  of  the  yeast  increases  in  the  fermentation  of  the  juice 
of  the  grape  and  beer-wort ;  but  if  we  put  the  yeast  in  a  solution  of  pure  sugar 
and  water,  although  the  fermentation  is  equally  produced,  the  yeast,  in  this  case, 
instead  of  gaining,  loses  a  portion  of  its  weight ;  and  by  continuous  contact  of  the 
same  yeast  with  fresh  sugar  and  water,  it  by  degrees  entirely  loses  the  power  of 
fermenting,  while  its  weight  constantly  diminishes.  In  this  case,  as  we  see,  one 
and  the  same  action  must  be  derived  from  two  directly  opposite  causes,  to  one  of 
which  is  ascribed  the  capacity  for  increase,  and  to  the  other  the  reverse  of  propa- 
gation. If  we  a-ssume  that  the  nutritive  and  re-spiratory  processes  of  the  fungi  are 
dependant  upon  sulphurous  and  nitrogenous  substances  contained  in  their  elements, 
and  that  the  fermentation  of  sugar  is  an  accidental  phenomenon,  accompanying 
the  developing  process  of  an  organic  being,  then  it  is  quite  incomprehensible  whence 
it  arises  that  the  fungi  are  not  reproduced  in  a  fluid,  where  there  is  present  this 
chief  requirement  to  their  propagation,  while  they  gain  in  weight  as  soon  as  sugar, 
the  accidental  attendant  of  this  vital  process,  is  added.  If,  for  instance,  in  the 
juice  of  the  grape,  sugar  be  decomposed,  and  there 'is  no  free  access  of  air,  the 
remainder  of  the  dissolved  sulphurous  and  nitrogenous  substances  will  remain 
dissolved  in  the  juice  for  years  without  undergoing  any  change  ;  if  sugar  be  then 
added,  the  fermentation  begins  again,  and  yeast  is  again  separated  ;  when  the  sugar 


32  CHEMISTRY  AND  PHYSICS  IN  RELATION 

is  decomposed,  its  separation  ceases,  beginning  again  only  on  a  new  addition  of 
sugar ;  and  this  continues  until  the  fluid  contains  an  excess  of  sugar. 

THE  FORMATION  OF  YEAST,  ALCOHOL,  AND  CARBONIC  ACID  ARE 
MUTUALLY  DEPENDENT  UPON  EACH  OTHER. 

From  these  facts  we  evidently  obtain  a  reciprocal  relation  of  dependence,  as 
required  by  chemical  theory,  between  the  form  and  properties  of  the  sulphurous 
and  nitrogenous  body  which  is  converted  into  yeast,  and  the  new  forms  and  pro- 
perties contained  in  the  atom  of  sugar ;  and  it  is  clear  that  the  condition  in  which 
the  elements  of  the  former  s-tand  during  their  association  with  the  yeast,  and  their 
falling  asunder  into  other  products,  is  the  cause  of  the  manner  in  which  the  sugar 
separates.  No  organic  beings  or  animals  similar  to  fungi,  have  ever  been  observed 
in  any  other  form  of  separation  of  sugar,  as,  for  instance,  in  its  transition  into 
lactic  acid  by  means  of  an  animal  membrane,  or  in  its  transition  into  mannit,  gum, 
butyric  acid,  acetic  acid,  &c. ;  nor  in  any  other  process  of  putrefaction  or  fermen- 
tation, have  organic  beings  been  perceived,  which  appearing  invariably  in  the  same 
forms,  control  the  nature  of  the  products. 


VIBRIONES  IN  THE  URINE. 

In  many  cases  the  presence  of  vibriones  is  detected  in  the  urine  during  its  state 
of  putrefaction,  while  in  other  cases,  when  the  urine  putrefies,  it  is  impossible  to 
discover  any  organized  being,  and  if  the  absence  of  vegetable  or  animal  organism 
is  certain  in  one  single  case,  where  fresh  urine  has  been  decomposed  by  the 
putrefying  white  deposit  which  occurs  in  a  state  of  putrefaction,  the  fact  is  per- 
fectly sufficient  to  remove  every  doubt  of  the  true  cause  of  the  putrefaction. 


FUNGI  CONTAIN  SUGAR. 

If  further  we  show  that,  in  all  hitherto  examined  fungi,  analysis  has  yielded  a 
quantity  of  sugar,  which  during  the  process  of  life  did  not  pass  into  alcohol  and 
carbonic  acid,  but  that,  in  the  same  fungi,  spirituous  fermentation  occurs  imme- 
diately after  their  death,  and  from  the  moment  when  a  change  in  the  color  and 
properties  is  perceived,  every  analogy  is  wanting  to  justify  our  regarding  the  vital 
process  of  these  plants  as  the  cause  of  fermentation.  The  action  must  rather  be 
ascribed  to  the  reverse  of  a  vital  process.* 


CHANGE  IN  THE  PROCESS  OF  PUTREFACTION  IN  HEATED  AIR. 

We  may  consider  it  as  proved  by  the  most  admirable  experiments,  that  the 
process  of  putrefaction  in  meat  and  many  other  animal  substances  assumes  a  totally 
different  form,  when  these  substances  have  been  preserved  in  vessels  containing 
heated  air,  and  when  consequently  there  can  be  no  co-operation  of  infusoria  ;  yet 
these  animal  substances  by  no  means,  under  these  circumstances,  maintain  their 
original  condition  ;  they  change  their  color  and  composition,  and  if  the  water 
necessary  to  complete  decomposition  of  the  meat  be  present,  it  dissolves  after  a 
certain  period  into  a  most  offensive  mass.f  We  need  only  recall  to  mind  the 

*  Schlossberger,  Annalen  dlir  Pharmacie,  Vol.  lii.  p.  117. 

f  De  Saus&ure  in  his  beautiful  investigations  observed  the  fact  that  hydrogen  at  a 
glowing  heat  obtained  by  the  decomposition  of  aqueous  vapour  by  means  of  iron,  and 


TO  PHYSIOLOGY  AND  PATHOLOGY.  33 

relations  of  fresh  urine  in  order  to  perceive  that  in  many  of  these  animal  substances 
a  constantly  renewed  afflux  of  oxygen  is  a  requirement  for  their  putrefaction ;  that 
on  the  exclusion  of  oxygen,  the  urea  does  not  pass  into  carbonate  of  ammonia, 
and  that,  enclosed  in  a  vessel,  these  substances  convert  the  oxygen  into  carbonic 
acid,  and  that  with  the  removal  of  the  oxygen,  the  whole  process  is  arrested,  or,  at 
all  events,  changed. 

The  adherents  of  the  parasite  theory  assume,  that  by  the  passing  contact  of 
sugar  of  grapes  with  the  air,  (without  which  fermentation  could  not  begin,)  the 
germ  of  the  yeast  plant  which  are  present  everywhere  in  the  air,  find  access  to  a 
soil  which  affords  them  the  necessary  requirements  for  their  fruitful  development ; 
but  they  do  not  explain  the  reason  why  the  brewer  is  obliged  to  add  yeast  in  order 
to  turn  his  wort  to  a  state  of  fermentation ;  and  why  these  same  germs,  if  they 
really  were  in  the  air,  should  not  develope  themselves  in  a  soil  so  congenial  to 
the  requirements  of  their  life  and  propagation.  They  entirely  forget  that  the  fer- 
mentation of  the  sugar  of  grapes  begins  with  a  chemical  action,  that  a  measureable 
quantity  of  oxygen  is  taken  up  from  the  air,  that  the  juice  becomes  turbid  and 
discolored,  and  the  fermentation  only  begins  after  the  occurrence  of  a  precipitate  ; 
they  do  not  consider  that  fermentation  diminishes  instead  of  increasing  with  the 
additional  quantity  of  oxygen ;  and  that  under  certain  conditions  when  the  matter 
capable  of  taking  up  oxygen  has  become  insoluble,  fermentation  no  longer  goes  on 
in  the  juice.* 

Before  all  these  relations  have  been  thoroughly  examined,  it  would  be  contrary 
to  all  sober  inquiry  to  consider  the  vital  process  of  an  animal  or  plant  as  the  cause 
of  any  process  of  fermentation  or  putrefaction ;  and  in  all  cases  where  the  pre- 
sence of  organic  beings  is  not  to  be  shown  on  investigation  in  the  contagion  of  a 
miasmatic  contagious  disease,  the  hypothesis  of  these  bodies  having  or  taking  any 
share  in  the  process  of  disease  must  be  rejected  as  altogether  unsound. 

TWO  SIMULTANEOUSLY  OCCURRING  PHENOMENA  ARE  FREQUENTLY 
HELD  TO  BE  A  CAUSE,  AND  ITS  EFFECT. 

Another  no  less  grave  error  in  the  mode  of  considering  and  deciding  upon  a 
question,  is  to  look  upon  different  phenomena,  which  are  effects  of  one  and  the 
same  cause,  as  mutually  dependent  upon  each  other,  and  regarding  the  description 
of  the  one  phenomena  as  an  explanation  or  definition  of  the  other. 


EXAMPLES. 

This  is  the  case,  for  instance,  with  the  explanation  which  is  given  of  fever,  of 
crises,  <fec.  A  few  examples  of  similarly  false  combinations,  which  daily  occur  in 
life,  will  best  exhibit  what  is  here  alluded  to. 


in  contact  with  putrifying  or  decayed  animal  substances  entered  into  no  combination 
with  oxygen  ;  while  at  the  ordinary  temperature,  pure  hydrogen  was  easily  condensed 
under  these  circumstances.  This  deserves  attention  in  an  inquiry  into  the  influence  of 
heated  air  upon  the  process  of  putrefaction.  Possibly  the  decomposition  of  infusoria 
and  the  germs  of  fungi  may  not  be  the  only  cause  of  the  change  in  this  process. 

*  Two  cubic  centimeters  of  must,  three  millimeters  thick  and  thirty  millim.  in  dia- 
meter, in  contact  with  twenty  cubic,  centim.  of  oxygen  do  not  pass  into  a  state  of 
fermentation  ;  while  a  similar  stratum  without  the  addition  of  oxygen  occasions  a  con- 
siderable development  of  carbonic  acid. — De  Saussure  in  the  Jahrbuch  fur  Chernie,  voL 

Ixiv.  pp.  47 — 51.  i 

• 

3 


34  CHEMISTRY  AND  PHYSICS  IN  RELATION 


A  STORM  REGARDED  AS  THE  CAUSE  OF  UNUSUAL  CHANGES  IN  THE 
STATE  OF  THE  BAROMETER. 

Nothing  is  more  common  than  the  opinion  which  ascribes  to  storms  the  effect 
of  making  the  mercury  fall  in  the  barometer. 

Storms  are  effects  of  a  difference  of  temperature,  or  of  some  other  causes  of 
interrupted  equilibrium  of  the  pressure  of  the  atmosphere.  A  change  of  the 
pressure  of  the  atmosphere  exhibits  itself  by  its  influence  upon  the  rise  and  fall  of 
a  column  of  mercury,  which  is  of  equal  weight  with  a  column  of  air  of  the  same 
diameter.  The  barometer  and  the  storm  do  not  stand  in  any  immediate  relation  to 
each  other ;  the  storm  exercises  no  influence  upon  the  barometer,  and  the  two  are 
only  combined  by  their  mutual  dependence  upon  one  cause.  And,  in  precisely  the 
same  manner,  the  fall  of  the  barometer  is  connected  with  the  occurrence  of  rain. 


SYMPTOMS  OF  FEVER  MUST  NOT  BE  REGARDED  AS  THE  CAUSES 
FROM  WHENCE  IT  ARISES. 

R 

The  false  ideas  which  many  pathologists  have  formed  to  themselves  of  the  cause 
of  fever,  belong  to  this  class  of  errors  regarding  the  causa  efficiens,  and  to  the 
confusion  of  ideas  concerning  effect  and  cause. 


HENLE'S  EXPLANATION  OF  FEVER. 

"Although  I  am  far  from  thinking,"  says  Henle,*  "that  I  am  able  to  settle  the 
controversy  regarding  the  question  of  the  existence  of  essential  fevers,  I  yet  believe 
I  may  contribute  something  that  shall  enable  the  contending  parties  first  to  under- 
stand themselves  better,  and  next  their  opponents.  It  follows  that  as  febrile 
symptoms  are  the  consequences  of  an  alteration  in  the  central  organ,  so  this 
alteration  is  the  proximate  cause  of  the  febrile  symptoms;  and,  as  the  fever  depends 
upon  these  symptoms,  upon  the  complication  of  the  change  of  temperature,  motion 
of  the  blood,  of  thirst  and  lassitude,  this  alteration  must  be  the  proximate  cause  of 
the  fever — in  fact  the  fever  itself." 

Setting  aside  that  these  three  positions  are  not  consecutive  links  of  one  conclu- 
sion, since  each  one  says  the  same  as  the  other  two — we  cannot,  in  accordance 
with  the  rules  of  natural  investigation, — so  long  as  the  causal  connection  of  the 
febrile  symptoms  and  the  alteration  in  the  spinal  cord  be  not  explained — regard 
the  febrile  symptoms  as  any  thing  more  than  indications  of  the  changed  condition 
of  the  spinal  cord.  To  the  symptoms  of  fever  which  are  externally  perceptible, 
must  be  added  the  scientific  investigation  of  a  new  indication  of  disease.  The 
alteration  in  the  central  organs  is  a  fact  perceived,  or  to  be  perceived,  by  the  senses, 
but  not  a  cause. 


WHAT  COURSE  MUST  BE  PURSUED  IN  THE  INVESTIGATION  OF  THE 

CAUSE  OF  FEVER. 

If  it  be  assumed  that  this  alteration  is  always  and  unalterably  accompanied  by 
febrile  symptoms,  the  knowledge  and  explanation  of  the  cause  of  fever  must 
include  the  recognition  of  the  connection  of  the  three  constantly  recurring  indica- 
tions of  fever — that  is,  the  subjective  feeling  of  indisposition,  the  alterations  in 

*  Untersuchungen,  p.  240. 


TO  PHYSIOLOGY  AND  PATHOLOGY.  35 

circulation  and  respiration,  and  the  changed  phenomena  of  heat,  which  characterize 
the  febrile  condition,  as  well  as  the  relation  of  their  mutual  dependence. 

If  we  exclude  from  investigation,  as  inexplicable  phenomena,  the  subjective 
indications,  the  feelings  of  indisposition,  and  of  heat  and  cold,  it  still  remains  to 
trace  the  connection  existing  between  the  alteration  of  the  spinal  cord,  the 
accelerated  movements  of  the  blood  and  the  respiratory  apparatus,  and  the  altered 
phenomena  of  heat.  Before  we  can  obtain  any  explanation  of  this,  we  must 
arrive  at  a  conception  of  motion,  and  seek  the  source  of  a  moving  force  and  heat 
in  the  animal  body.  If  we  could  trace  the  cause  of  fever  according  to  the  physical 
method,  and  consider  that  by  the  co-operation  of  many,  or  let  us  say  of  two 
causes,  a  certain  amount  of  force  is  engendered  in  the  heart  itself,  by  which  the 
circulation  of  the  blood  is  affected  ;  then  the  motion  will  be  regular  or  normal,  if 
the  number  of  the  beats  of  the  heart  be  equal  in  every  minute,  and  when  the 
force  is  thus  divided  over  equal  periods. 


POINT  OF  VIEW  OF  THE  INVESTIGATION. 

If  this  same  amount  of  force,  in  consequence  of  the  disturbed  relation  of  the 
two  causes,  which  have  their  seat  in  the  heart,  at  one  time  increases  and  at  another 
diminishes,  the  pulsations  of  the  heart  will  be  at  one  time  quicker,  and  at  another 
slower.  The  force  engendered  is  in  this  case  not  proportionate  to  the  term  of  its 
consumption.  It  is  clear  that,  on  the  supposition  of  this  force  being  engendered  in 
the  heart,  the  alteration  in  the  spinal  cord  can  exercise  no  other  influence  upon  the 
change  in  the  phenomena  of  motion,  or  upon  the  accelerating  or  retarding  of  the 
heart's  action,  than  that,  in  consequence  of  its  condition,  it  may  oppose,  in  some 
manner  or  other  a  smaller  resistance  to  motion  at  one  period  than  at  another.  The 
causes  of  the  effects  of  motion  do  not  exist  in  the  heart  alone ;  they  are  distributed 
in  every  part  of  the  organism,  in  the  spinal  cord,  as  well  as  in  every  individual 
muscular  fibre. 


INQUIRY  INTO  THE  CONNECTION  OF  THE  SPINAL  CORD  WITH 
THE  EFFECTS  OF  MOTION. 

We  may  conjecture  that  the  movement  of  the  heart,  as  well  as  that  of  all  other 
parts  of  the  organism,  the  motion  of  the  intestines,  and  the  voluntary  motions, 
proceed  from  the  spinal  cord,  and  it  is  evident  that  a  change  in  the  condition  or 
character  of  this  organ  must  be  followed  by  a  change  in  all  the  phenomena  of 
motion.  The  same  must  happen  when  any  part  of  the  nerves,  standing  in 
connection  with  the  spinal  cord,  and  with  the  circulatory  apparatus,  &c.,  suffers  a 
change  of  condition  or  properties,  and  this  changed  activity  must  exercise  a  retro- 
grade influence  upon  the  spinal  cord  and  the  apparatus  of  motion.  The  laws  of 
the  propagation  or  communication  of  motion,  are  every  where  the  same,  whatever 
causes  may  have  called  them  forth. 

The  cause  of  motion  in  a  mill,  the  rotatory  motion  of  the  stone,  the  bolting 
of  the  flour,  &c.,  are  not  occasioned  by  the  wheel,  for  that  is  a  portion  of 
the  mill  itself.  It  is  quite  certain  that  an  irregularity  in  the  working  of  the 
mill  may  be  occasioned  by  the  removal  of  a  few  of  the  wings  of  the  wheel, 
by  which  the  pressure  of  the  water  on  these  parts  ceases  ;  it  may  also,  however, 
be  occasioned  by  the  breaking  off  of  the  cogs  of  one  of  the  other  wheels  of  the 
mill,  when  an  irregularity  of  motion  will  be  perceived  not  only  in  this  wheel,  but 
in  every  other  part  of  the  wheel. 


36  CHEMISTRY  AND  PHYSICS  IN  RELATION 

REGULAR  AND  IRREGULAR  MOTIONS, 

If  now  the  organism  engender  a  certain  amount  of  force  in  a  given  time,  the 
motions  will  be  regular,  if  the  force  proceed  from  the  spinal  cord ;  irregular,  if  one 
apparatus  have  more  force  than  another.  If  subsequently  the  motions  of  the  blood 
and  respiration  be  accelerated,  the  consequence  will  be  weakness  in  the  limbs,  or  a 
disturbance  of  the  digestive  functions.  The  extra  force  which  the  heart  receives 
in  the  acceleration  of  its  action,  cannot  be  applied  to  the  other  apparatus  of 
motion. 

After  establishing  the  connection  between  the  spinal  cord  and  the  effects  of 
motion,  the  relations  of  the  latter  to  the  phenomena  of  animal  heat  must  next  be 
discussed. 


RELATION  OF  THE  PHENOMENA  OF  ANIMAL  HEAT  TO  THOSE 

OF  MOTION. 

Observations  show  that  the  irregularity  of  the  phenomena  of  motion  is  accom- 
panied by  a  change  in  the  phenomena  of  heat ;  in  many  cases  the  subjective  and 
objective  phenomena  of  heat  rise  and  fall  with  the  acceleration  or  retardation  of 
the  indication  of  motion  ;  in  other  cases,  again,  both  do  not  recur  simultaneously  in 
the  same  relations.  But  the  phenomena  of  motion  become  more  regular  by  the 
equalization  of  the  indications  of  heat ;  and,  if  the  former  are  restored  to  a  normal 
state,  the  latter  will  show  a  proportionate  degree  of  irregularity.  If,  now,  it  can 
be  shown  that  the  effect  of  motion  (speed)  does  not  call  forth  heat,  (as,  for  instance, 
by  friction,)  it  naturally  follows,  that  heat  and  the  phenomena  of  motion  stand  in 
no  nearer  connection  with  each  other,  than  the  storm  with  the  abnormal  rise  and 
fall  of  the  mercury  in  the  barometer  ;  and  that,  consequently,  the  causes  which 
have  influenced  the  one  series  of  phenomena  are  simultaneous  conditions  of  the 
other  series.  If  the  amount  of  evolved  heat,  in  a  given  time,  stand  in  a  definite  rela- 
tion to  the  number  of  blood  corpuscles  which  have  passed  through  the  capillaries 
in  the  same  time,  the  source  of  heat  must  be  sought  in  certain  states  of  the  blood- 
corpuscles,  or  of  the  blood  and  the  capillaries. 

RELATION  OF  THE  PHENOMENA  OF  HEAT  TO  THE  OXYGEN  OF 

THE  AIR. 

Since  it  is  proved,  by  investigation,  that  the  condition  of  the  blood,  by  which  it 
may  become  a  source  of  heat,  consists  in  its  power  of  taking  up  oxygen,  and 
since  the  oxygen  thus  taken  up  in  a  given  time  stands  in  a  definite  relation  to  the 
number  of  inspirations  within  the  same  period,  irregular  effects  of  heat  must  be 
dependent  upon  the  respiratory  motions,  the  contractions  of  the  heart,  and  one 
external  cause — and  this  is,  the  chemical  action  of  oxygen.  As  the  relation  of 
these  three  factors  to  each  other  is  altered,  the  phenomena  of  heat  must  in  like 
manner  change ;  and  when  in  certain  parts  of  the  organism  the  capacity  of  enter- 
ing into  combination  with  the  oxygen  increases  from  any  superadded  cause,  more 
heat  will  be  evolved  in  that  one  part  than  in  others.  When,  in  accordance  with 
this,  the  motion  of  the  circulation  and  respiration  is  accelerated,  then  will  also  the 
amount  of  oxygen  and  liberated  heat  be  increased,  which  is  in  accordance  with 
the  beautiful  law  established  by  Vierordt.  If  the  respiratory  and  circulatory 
motions  are  accelerated  in  unequal  relations,  the  subjective,  or  objective  feeling  of 
warmth  is  changed.  When  all  these  relations  are  examined  and  obtained,  we  shall 
not  only  be  able  to  explain  the  individual  symptoms  of  the  fever,  and,  conse- 
quently, the  disease  itself,  but  we  shall  then  also  be  enabled  to  trace  all  to  a  filial 
and  sole  cause  (the  cause  of  disease).  This  is  the  course  of  natural  inquiry. 


TO  PHYSICS  AND  PATHOLOGY.  37 


ERRONEOUS  CONCLUSIONS  DRAWN  FROM  BRINGING  ONE  CAUSE 
TOO  PROMINENTLY  FORWARD. 

Erroneous  combinations  of  conclusions  of  another  kind  are  formed,  when  in  the 
explanation  of  a  natural  phenomenon  we  only  keep  in  view  one  of  the  many 
causes  on  which  it  is  dependent,  ascribing  to  it  an  active  importance  which  it  does 
not  possess  in  and  for  itself,  but  merely  receives  from  the  presence  of  other  causes. 
Thus,  for  instance,  Schleiden  bases  his  theory  partly  upon  an  untenable  atomism, 
partly  upon  false  mechanical  principles,  when  he  says,  in  his  "  Elements  of 
Scientific  Botany,"*  "that  fermentation  and  putrefaction  are  the  effects  of  the 
communication  of  a  motion,  and  that  the  amount  of  the  motion  will  be  measured 
by  the  product  of  the  mass  into  the  velocity.  One  part  of  diastase  is  said  to 
extend  its  decomposing  power  over  1000  parts  of  starch  (but  this  is.  an  error, 
since,  according  to  Guerrin  Varry,  one  portion  of  diastase  acting  upon  60  of  starch, 
gives  only  10.3  of  sugar.  The  relation  of  16  of  starch  to  1  of  diastase,  gives 
only  14  of  sugar.)  We  must,  therefore,  assume  in  an  atom  of  diastase  a  velocity 
1000  times  greater  than  would  be  necessary  for  the  decomposition  of  an  equal 
weight  of  starch.  Here  we  see  that  a  gigantic  edifice  of  crowded  hypotheses  has 
been  erected  upon  the  most  untenable  basis,  in  order  to  support  a  false  opinion. 
On  the  other  hand,  the  objection  started  as  to  the  impossibility  of  one  body  at  rest 
setting  another  in  motion,  borrowed  from  the  atomic  method  of  explanation,  is 
likewise  physically  false ;  since  gravitation,  magnetism,  and  electrical  attraction 
are  nothing  but  mere  examples  of  motion  being  imparted  by  one  body  at  rest  to 
another." 

CORRECTION  OF  SCHLEIDEN'S  VIEW. 

As  to  what  regards  diastase,  and  its  action  upon  starch,  Schleiden  has  forgotten 
to  take  into  consideration  the  time  which  is  necessary  to  effect  the  conversion  into 
sugar.  The  view  which  he  contests,  does  not  presuppose  that  the  molecules  of 
the  diastase  possess  a  greater  velocity,  but  that  the  surrounding  deposition  of  the 
molecule  of  starch  had  gone  on  while  the  motion  in  the  diastase  molecule  still 
continued,  and,  consequently,  before  a  state  of  equilibrium  had  been  established  in 
the  latter.  Nothing  is  to  be  understood  by  a  communication  of  motion,  but  that 
the  molecules  of  starch  are  kept  in  contact  with  the  molecules  of  the  diastase,  as 
if  they  were  parts  or  constituents  of  it.  The  action  of  the  diastase  in  a  limited 
time  depends,  therefore,  upon  the  number  of  the  molecules  of  starch  that  can  come 
in  contact  with  the  molecules  of  the  diastase  in  the  same  period  of  time.  The 
number  of  the  molecules  of  diastase  affect  the  time  and  the  process  of  its  conver- 
sion into  sugar ;  the  action  disappears  with  the  presence  of  diastase,  and  by  a 
double  or  triple  quantity  of  diastase  the  time  of  the  conversion  is  shortened,  or  a 
larger  quantity  of  starch  is  converted  in  sugar. 

THE  MEANS  BY  WHICH  MOTION  OCCURS. 

As  to  the  view  advanced  regarding  gravitation  and  electricity,  as  instances  of  the 
motion  of  one  body  through  another  at  rest,  we  must  take  into  consideration 
that  a  body  at  rest  may  pass  into  a  condition  of  motion  in  two  essentially  different 
modes. 

FIRST :  BY  THE  COMMUNICATION  OF  A  MOVING  MASS. 

1.  By  the  communication  of  the  moving  mass  of  a  body  already  in  motion,  as 
by  means  of  a  blow — for  instance,  the  action  of  the  hammer  on  the  nail,  of  water 
on  the  mill  wheel,  or  wind  upon  the  sail. 

*  Grundzuge  der  Wissenschaftlichen  Botanik,  1845,  p.  282. 


38  CHEMISTRY  AND  PHYSICS  IN  RELATION 


SECONDLY :  BY  AN  ATTRACTIVE  OE  REPULSIVE  FORCE, 

2.  By  the  action  of  an  attractive  or  repulsive  force,  which  is  interposed  between 
two  bodies.  In  this  the  action  is  always  mutual,  and  the  speed  obtained  inversely 
proportionate  to  the  masses  moved. 

CHEMICAL  PROCESSES,  AS  PHENOMENA  OF  MOTION,  BELONG  TO 
THE  SECOND  KIND, 

As  one  must  consider  chemical  processes  as  phenomena  of  motion,  it  is  not  to 
he  doubted  that  all  such  processes  as  can  be  explained  by  the  formation  of  new 
compounds  belong  to  the  second  class  of  phenomena  of  motion,  while  the  attractive 
f  re  f  th  constituents,  or  their  chemical  affinity,  calls  forth  the  change  of  place 
:-nd  prop  rty  (that  is  the  motion)  of  matter.  After  the  establishment  of  the  corn- 
bin  tio  ,  motion  ceases,  as  when  the  falling  stone  has  reached  the  ground,  and  the 
ir  n  filings  the  pole  of  the  magnet. 

PUTREFACTION  AND  FERMENTATION  BELONG  TO  THE  FIRST  ORDER 
OF  PHENOMENA  OF  MOTION. 

But  when  a  body  which  is  undergoing  decomposition,  that  is,  whose  parts  are 
in  a  state  of  change  of  place  and  of  motion,  converts  another  body  into  a  similar 
condition  ;  and  if  observation  have  shown  that  all  other  known  causes,  excepting 
one  alone,  must  be  excluded  from  any  participation  in  the  change,  or  decomposition 
of  the  second  body ;  and  if  it  be  proved  that  this  one  cause  (cpmmunication  of 
motion,  friction,  a  blow,  <fec.),  have  a  decided  share  in  the  formation  and  decom- 
position of  a  number  of  combinations,  this  one  cause  must  be  regarded  as  the 
final  acting  one,  especially,  if  the  views  gained  in  the  theory  of  motion,  be  appli- 
cable to  chemical  actions.  The  recognition  of  this  last,  and  only  cause,  is  there- 
fore not  a  mere  word  that  has  been  substituted  for  the  term  " catalytic  force;"  but 
Ithe  expression  of  an  idea,  which  is  strictly  the  opposite  to  that  of  a  catalytic  body. 
Prom  the  facts  advanced  in  (2)  p.  84,  the  erroneous  conclusion  is  drawn  that  gravi- 
tation, magnetism,  <fec.,  are  examples  of  the  motion  of  one  body  through  another 
at  rest. 

THE  FORCE  OF  GRAVITATION  GIVES  NO  RISE  IN  ITSELF  TO  MOTION. 

A  clock  is  kept  in  motion  by  the.  weight,  but  cannot  draw  it  up  by  itself,  and  the 
heat  of  the  sun  has  as  little  share  as  gravitation  in  the  action  of  a  mill-wheel.  The 
water  which  impels  the  mill-wheel  was  previously  vapour — the  vapour  was  fluid 
water. 

The  water  underwent  evaporation ;  the  vapour,  on  the  abstraction  of  heat,  be- 
came again  aqueous,  and  this  liquid  water  falls  by  the  action  of  gravitation,  and 
continues  to  fall  until,  as  in  the  clock,  resistance  arrests  its  motion. 

WANT  OF  CORRECTNESS  IN  EXPRESSION,  THE  CAUSE  OF  ERRONEOUS 
CONCLUSIONS  AND  MISUNDERSTANDINGS. 

Besides  the  erroneous  conclusions  and  methods  of  investigation  which  are  com- 
prised in  this  one  clause,  there  is  yet  one  individual  fault  to  be  added,  which  pre- 
vails amongst  many  physiologists,  and  which  can  be  explained  only  on  the  plea  of 
carelessness.  This  failing  is,  to  regard  things  or  phenomena,  that  have  been  per- 
ceived by  the  senses,  as  representing  conclusions  of  the  mind,  which  brings  along 
with  it  this  great  disadvantage,  that  in  order  to  esteem  a  fact  as  true,  these  natural- 
ists require  to  have  ocular  demonstration  of  known  causes  which  cannot  be  per- 
ceived by  the  senses. 

From  this  it  may  arise  that  chemists,  in  spite  of  a  superabundance  of  the  most 
evident  facts,  are  frequently  unable  to  convince  physicians  of  the  simplest  truths. 


TO  PHYSIOLOGY  AND  PATHOLOGY.  39 

EXAMPLES. 

Examples  of  this  assertion  can  be  found  in  every  physiological  work ;  and  I  will 
give  a  few  illustrations  from  one  of  the  most  recent  treatises.  Valentin  says,* 
"  We  perceive  on  dividing  the  facial  nerve,  that  the  muscles  of  the  face  on  the  cor- 
responding side  are  paralysed  as  far  as  the  will  is  concerned.  We  thence  justly 
conclude  that  the  effects  of  our  will  are  communicated  by  means  of  the  facial  nerve 
to  the  muscles  of  expression. 

"  We  find,  after  injury  of  the  trunk,  or  the  branch  of  the  fifth  pair  of  nerves 
supplying  the  eye,  that  secondary  inflammation,  suppuration,  and  even  further, 
destruction  of  the  globe  of  the  eye,  are  occasioned ;  and  conclude,  therefore,  that 
the  integrity  of  the  above-named  nerves  is  necessary  to  the  normal  condition  of 
the  eye." 

Further  on,  at  page  3,  we  find  as  follows :  "  I  know  that  the  walls  of  the  arteries 
are  elastic,  and  I  may,  therefore,  at  once  conclude  that  they  distend  to  a  certain 
extent  as  soon  as  they  have  been  filled  with  blood  ;  and  that  on  the  yielding  of  the 
pressure  they  return  to  their  original  circumference  ;"  that  is  to  say,  they  are  elastic. 

POINT  OF  CONTACT  BETWEEN  PHYSIOLOGY  AND  CHEMISTRY. 

I  have  shown  in  the  above,  how  much  the  difference  in  the  way  of  viewing 
things,  adds  to  the  difficulty  of  arriving  at  an  understanding  between  physiologists 
and  chemists ;  and  I  will  now  endeavor  to  consider  more  particularly  the  point 
of  contact,  at  which  physiology  and  chemistry  ought  to  meet  in  order  that  they 
may  mutually  assist  each  other. 

DEVIATION  OF  CHEMICAL  AND  MECHANICAL  LAWS  FROM  THE 
LAWS  WHICH  GOVERN  VITAL  PHENOMENA. 

If  we  endeavor  to  make  use  of  illustrations  derived  from  the  knowledge  of 
mechanical  forces,  in  the  inquiry  of  vital  or  chemical  phenomena,  we  immediately 
observe  that  the  laws  which  govern  the  former,  differ  in  many  respects  from  those 
on  which  the  peculiarities  of  chemical  or  vital  combinations  are  dependent. 

RELATION  OF  THE  PROPERTIES  OF  ELEMENTS  TO  THE  PROPERTIES 
OF  THEIR  COMBINATIONS. 

A  chemical  combination  of  two  bodies,  possesses  properties  which  are  entirely 
different  from  those  of  its  several  constituents.  The  chemical  force  of  the  new 
body,  the  power  of  entering  into  new  combinations,  or  bringing  about  decompo- 
sition, is  not  the  sum  of  the  chemical  forces  of  its  elements.  We  are  entirely 
unable,  by  tracing  backwards,  from  the  properties  of  a  muscular  fibre,  to  decide 
concerning  those  of  carbon,  hydrogen,  nitrogen,  and  its  other  elements ;  and  yet 
nothing  can  be  more  true,  than  that  certain  relations  remain  permanent  between  the 
properties  of  the  elements,  and  those  of  their  combinations. 

Cinnabar  is  a  metallic  sulphuret,  which  possesses  totally  different  properties  from 
sulphuret  of  lead  on  sulphuret  of  zinc.  It  cannot  be  doubted  that  their  difference 
is  dependant  upon  the  fact  of  mercury  being  combined  in  the  first,  lead  in  the 
second,  and  zinc  in  the  third,  with  sulphur;  and  that  the  properties  of  the  mercury, 
lead,  and  zinc,  must  have  an  entirely  definite  and  definable  share  in  the  difference 
of  the  properties  of  their  combinations,  since  the  latter  are  evidently  dependent 
upon  the  difference.  We  see  this  the  most  clearly  in  the  isomorphous  substances  ; 
sulphuret  of  lead  is  scarcely,  in  appearance,  to  be  distinguished  from  seleniuret  of 
lead,  sulphate  of  alumina  and  ammonia,  from  sulphate  of  alumina  and  potash, 
selenate  of  soda,  from  sulphate  of  soda.  The  relations  which  exist  between  the 

*  Manual  of  Physiology,  Brunswick,  1844. 


40  CHEMISTRY  AND  PHYSICS  IN  RELATION 

chemical  and  physical  properties  of  the  elements  have  remained  constant  in 
many  of  these  combinations ;  and  in  those,  where  there  is  a  deviation  in  color, 
solubility,  &c.,  one  property,  namely,  physical  form,  remains  constant.  The  same 
or  a  similar  relation  is  doubtlessly  attainable  between  the  properties  of  all  elements 
and  their  combinations,  and  all  the  efforts  of  chemistry  have  been  directed  to  the 
discoveries  of  these  constant  relations.  An  investigation  of  this  kind  is  the  only 
way  in  which  chemistry  can  attain  to  natural  laws,  and  it  is  only  by  the  same 
means  that  physiology,  if  it  is  to  rise  to  the  rank  of  a  natural  investigation,  can 
gain  a  scientific  basis. 

THE  CHEMICAL  FORCES  OF  THE  ELEMENTS  HAVE  A  SHARE 
IN  THE  VITAL  PROPERTIES. 

We  cannot,  certainly,  as  yet,  follow  out  any  physical  property  by  means  of  the 
laws  or  properties  of  the  elements  ;  but  still  there  can  be  no  question,  that  a 
knowledge  of  such  properties  is  to  be  gained  from  laws,  which  arise  when  these 
elements  have  been,  in  a  certain  measure,  arranged.  When  these  elements  have 
combined  to  form  an  animal  or  vegetable  substance ;  when  they  have  attained  to 
physiological  or  vital  properties ;  then  the  chemical  forces,  which  have  given  them 
their  original  properties  are  no  more  destroyed  or  removed,  than  the  cohesive 
power  of  the  atoms  of  sulphur  is  destroyed  when  we  melt  a  portion  of  that 
substance.  There  has  only  been  another  cause  superadded — heat — which  has 
removed  the  effect  of  the  cohesive  force,  or  the  connection,  rendering  its  action 
no  longer  perceptible.  The  new  condition,  that  of  fluidity,  is  one  of  equilibrium 
between  two  antagonising  causes,  an  effect  in  which  both  have  an  equal  share. 

In  vegetable  and  animal  substances,  the  elements  obey  mechanical  and  chemical 
laws,  if  their  action  be  not^removed  by  resistances,  which  must  be  regarded  as  the 
indications  of  new  laws,  that  govern  the  parts  of  the  organism. 

THE  RELATIONS  BETWEEN  CHEMICAL  AND  VITAL  EFFECTS  MUST 

BE  INVESTIGATED. 

If  by  the  connection  of  many  causes,  new  laws  and  phenomena  are  brought 
forward,  which  have  no  resemblance  with  the  actions  of  individual  causes  in 
themselves,  the  effects  of  the  latter  stand  in  an  immediate  relation  to  those  of  the 
new  phenomena,  and  these  are  the  relations  which  must  be  sought  and  investigated. 

When  we  have  gained  a  clear  conception  of  these,  we  shall  be  able  to  decide 
concerning  a  number  of  unknown  facts  or  phenomena,  as  in  the  case  of 
isomorphous  substances,  without  further  observation. 

THE  RELATION  OF  THE  WEIGHTS  OF  THE  ELEMENTS  TO  CHEMICAL 

COMBINATIONS. 

A  purely  scientific  character  has  been  imparted  to  chemistry  by  the  knowledge 
of  the  fact,  that  the  property  of  weight  in  all  chemical  combinations  is  constant, 
and  that,  in  whatever  manner  the  elements  may  be  composed,  the  weigh' t  of  the 
combination  is  equal  to  the  sum  of  the  weight  of  its  elements.  The  knowledge 
of  chemical  proportions  has  led  to  our  being  able  to  predetermine  all  possible 
combinations  of  a  body;  but  it  could  not  explain  the  apparent  exceptions  of  bodies, 
which,  according  to  experience,  united  not  in  constant,  but  in  every  conceivable 
proportions.  It  is  by  the  consideration  of  -another  property — the  relation  of 
external  form  to  composition — that  we  have  not  only  been  enabled  to  give  an 
explanation  of  these  deviations,  but  have  also  gained  a  far  clearer  conception  of 
the  cau?e  of  the  £pjisia*rt"relations  of  combination. 

THE  UNIVERSALITY  OF   LAWS  OF  MUTUAL  DEPENDENCE 
IN  NATURAL  PHENOMENA. 

The  advances  made  in  all  branches  of  natural  investigation,  in  the  physical 


TO  PHYSIOLOGY  AND  PATHOLOGY.  41 

sciences,  as  well  as  in  physiology,  rest  upon  the  conviction  that  similar  laws,  based 
upon  conditions  in  the  properties  of  bodies  reciprocally  depending  upon  each 
other,  may  be  obtained. 

THE  WAY  TO  ATTAIN  TO  A  KNOWLEDGE  OF  THE  RELATIONS  OF 

DEPENDENCE. 

There  is  no  other  method  in  natural  investigation  by  which  we  can  arrive  at  a 
knowledge  of  the  relations  in  which  the  properties  of  bodies  stand  to  each  other, 
than  by  first  seeking  to  learn  these  properties  themselves,  and  next,  the  cases  in 
which  they  vary.  It  is  a  law  of  nature,  that  the  deviations  in  a  property  are, 
without  exception,  accompanied  by  entirely  similar  changes  in  another  property ; 
and  it  is  perfectly  clear,  that  the  knowledge  of  the  laws  of  these  deviations,  will 
place  us  in  a  position  to  decide  concerning  the  one  property,  without  any  further 
observation  of  the  other.  The  knowledge  of  the  one,  will  lead  to  the  explanation 
ef  the  other. 

A  few  examples  will  be  sufficient  to  prove  the  truth  of  these  statements. 

EXAMPLES  OF  THE  LAWS  OF  DEPENDENCE-PRESSURE  AND  THE 

BOILING  POINT. 

It  is  known  that  every  fluid  passes  into  a  state  of  ebullition  under  the  same 
circumstances,  and  at  unvarying  degrees  of  temperature  ;  this  is  so  constant,  that 
we  designate  the  boiling  point  as  a  characteristic  property  of  fluids. 

One  of  the  conditions  of  the  constant  temperature  at  which  air  bubbles  are 
formed  in  the  interior  of  these  fluids,  is  external  pressure  ;  the  boiling  point  varies 
with  this  pressure  in  all  fluids,  according  to  an  especial  law,  increasing  or  dimi- 
nishing with  the  increase  or  diminution  of  the  pressure.  Every  boiling  point  of 
temperature  has  a  corresponding  and  definite  pressure,  and  every  pressure  a  defi- 
nite temperature.  It  is  known  that  an  acquaintance  with  the  law  of  the  mu  u;tl 
dependence  of  the  boiling  point  of  the  water,  and  the  pressure  of  the  atmosphere 
has  led  to  our  being  able,  by  means  of  the  thermometer,  to  decide  altitudes  above 
the  level  of  the  sea,  and  thus  to  measure  one  property  by  deviations  in  the  other. 

THE  BOILING  POINT. 

The  relation  in  which  the  boiling  point  of  fluids  stands  to  their  properties  is  less 
known.  Pyroligneous  spirit,  alcohol,  and  the  fousel  oil  of  potato  spirit  are  three 
fluids,  possessing  very  different  boiling  points.  Pyroligneous  spirit  boils  at  138° 
F.,  alcohol  at  172°  F.,  fousel  oil  at  274°  F.  The  comparison  of  these  three 
boiling  points  shows  that  the  boiling  point  of  alcohol  is  34°  higher  than  that  of 
pyroligneous  spirit  (138° +34°  =  172°),  while  that  of  fousel  oil  is  four  times  34° 
higher  (138° +4x34°  =274°).  Each  of  these  three  fluids  yields  an  acid  upon 
oxidation  under  like  circumstances  :  pyroligneous  spirit  gives  formic  acid  ;  alcohol, 
acetic  acid ;  fousel  oil,  valerianic  acid.  Of  these  three  acids,  each  has  its  own 
boiling  point :  formic  acid  boils  at  210°  F.,  acetic  acid  at  249°  F.,  and  valerianir 
acid  at  347°  F.  If  we  compare  these  three  points,  we  find  that  they  stand  in  the 
same  relation  to  each  other,  as  do  the  boiling  points  of  the  fluids  from  which  thesf 
acids  have  been  obtained.  The  boiling  point  of  acetic  acid  is  34°  higher  than  thai 
of  formic  acid,  while  the  boiling  point  of  the  valerianic  acid  is  four  times  34°  higher. 

A  similar  deviation  in  one  property  shows,  as  we  have  remarked,  a  similar 
deviation  in  another.  The  property  to  be  considered  here,  is  the  composition.  F 
we  compare  the  composition  of  the  six  several  bodies  (of  the  three  acids,  and  th? 
three  fluids,)  from  which  they  originate  by  the  influence  of  oxygen,  we  find  as 
follows:  the  composition  of  the  pyroligneous  spirit  is  designated  by  the  formula, 
Cz  H4  O2 ;  that  of  spirits  of  wine  by  C4  H6  O2 ;  that  of  fousel  oil  by  C10  H12  O,. 


42  CHEMISTRY  AND  PHYSICS  IN  RELATION 

If  now  we  designate  by  R,  a  quantity  of  carbon  and  hydrogen,  which  belongs 
to  the  formula  C  H.  (like  equivalents),  we  see  immediately,  that  the  composition 
of  alcohol  can  be  expressed  by  that  of  pyroligneous  spirit-j-2  R. 

Pyroligneous  spirit,  Alcohol. 

C2H402+C2H2       =       C4H602. 

While  the  composition  of  fousel  oil  may  be  expressed  by  that  of  pyroligneous 
spirit  -f  8  R. 

Pyroligneous  spirit.  Fousel  oil. 

C2H402+C8H8       =       C12HK02. 

The  formula  of  formic  acid  is  C2  H2  O4,  that  of  acetic  acid  C4  H4  O4,  that 
of  valerianic  acid  C,0  H,0  O4.  We  easily  perceive  that  the  formula  of  the 
acetic  acid  can  be  expressed  by  that  of  formic  acid-f-2  R,  the  formula  of  valerianic 
acid  by  that  of  formic  acid  +  8  R.  In  accordance  with  these  experiments,  a 
boiling  point  increased  34°  F.  corresponds  with  the  occurrence  or  excess  of  2  equiv. 
of  carbon  and  2  equiv.  of  hydrogen,  or  of  2  R.  It  may  be  seen  that  the  relation 
between  this  group  is  constant,  and  that  a  conjecture  concerning  their  composition 
may  be  made  from  the  knowledge  of  the  boiling  point.  The  boiling  point  of  the 
formate  of  oxyde  of  methyle  is  96°  F.,  that  of  formate  of  oxide  of  aethyle,  100° 
F.,  the  difference  between  the  two,  34°.  From  this  it  might  be  conjectured  that 
the  composition  of  the  latter  differs  from  the  former  about  C2  H2  or  2  R,  and 
such  is  the  case,  The  formula  for  formate  of  oxide  of  methyle  is  C4  H4  O4, 
that  of  the  corresponding  compound  of  aethyle  C6  H6  O4,  and  therefore  about 
C2  H2  higher.  But  butyric  acid  boils  at  311°  F.,  and  its  boiling  point  is,  therefore, 
about  three  times  34°  higher  than  that  of  formic  acid.  The  comparison  of  their 
formulae  shows  that  butyric  acid  may  be  looked  upon  as  formic  acid  -f  6  R. 
Toluidine  and  aniline  are  two  organic  bases,  both  so  far  different  in  their  compo- 
sition, that  aniline  contains  C2  H2,  or  2  R  more  than  toluidine.  The  comparison 
of  their  boiling  points  shows  that  the  boiling  point  of  aniline  is  34°  higher. 

THE  LAW  OF  THE  RELATIONS  OF  DEPENDENCE  IS  DISTINCT  FROM 
THE  CAUSES  BY  WHICH  THESE  PHENOMENA  ARE  EFFECTED. 

No  one  will  deny,  from  these  examples,  the  existence  of  a  natural  law  for  this 
group,  nor  can  any  one  doubt  that  the  qualities  of  a  body  stand  in  a  definite  rela- 
tion to  its  composition,  and  that  a  change  in  a  quality  corresponds  with  a  similar 
deviation  in  its  quantitative  relations.  It  must  be  especially  noticed  here,  that  the 
knowledge  of  this  natural  law  is  quite  independent  of  the  actual  cause,  or  of  the  con- 
ditions which,  taken  together,  effect  the  constant  boiling  point,  for  we  are  as  ignorant 
of  what  relates  to  the  boiling  point,  as  we  are  concerning  the  conception  of  life. 

THE  BOILING  POINT,  THE  SPECIFIC  GRAVITY,  AND  THE  COMPOSI- 
TION OF  A  BODY  STAND  IN  RELATIONS  OF  DEPENDENCE  TO 
EACH  OTHER. 

In  the  above  examples  we  have  only  touched  upon  one  of  the  relations  of  the 
quality  and  composition  of  bodies,  there  being  as  many  of  these  relations  as  the 
body  has  properties.  A  law  has  been  obtained  for  a  large  group  of  chemico  organic 
combinations,  by  which,  from  the  knowledge  of  the  boiling  point,  and  the  compo- 
sition of  the  body,  it  has  been  established  how  many  pounds  a  cubic  foot  of  the 
combination  weighs,  and  that  the  property  of  the  specific  gravity,  and  consequently 
of  the  pressure  which  the  body  exerts  on  equal  spaces,  stand  in  a  definite  relation 
to  two  others,  which  are  changed  as  it  likewise  is  changed. 

SPECIFIC  HEAT  AND  ATOMIC  WEIGHT. 

A  similar  relation  of  dependence  has  been  established  in  reference  to  the  amount 
of  heat  which  different  bodies  need  in  order  to  rise  to  the  same  temperature,  and 


TO  PHYSIOLOGY  AND  PATHOLOGY.  43 

their  equivalent  weights.  It  is  a  well  known  fact,  that  different  bodies  receive  a 
different  amount  of  heat  at  the  same  temperature.  Equal  weights  of  sulphur,  iron, 
and  lead,  heated  to  the  boiling  point  of  water,  when  brought  in  contact  with  ice, 
melt  a  certain  quantity  of  it,  but  the  amount  of  water  produced  under  these 
circumstances  is  very  different. 

If  the  quantity  of  heat  were  equal  in  the  three  bodies,  the  weight  of  melted  ice 
must  amount  Wthe  same  in  all,  but  the  unequal  effect  which  is  here  observed 
proves  the  want  of  uniformity  in  the  active  cause.  Sulphur  melts  six  and  a  half 
times  as  much  ice  as  lead,  while  iron  melts  four  times  as  much.  It  is  perfectly 
clear,  that  when  we  heat  sulphur,  iron,  and  lead  at  the  same  difference  of  tempe- 
rature, say  for  example,  from  (60  to  400)  with  the  same  spirit  lamp,  we  should 
have  to  consume  half  an  ounce  of  spirit  to  heat  lead,  three  ounces  and  a  quarter 
of  an  ounce  for  the  same  quantity  of  surphur,  and  nearly  two  ounces  for  an  equal 
weight  of  iron. 

These  differences  in  the  amount  of  heat  required  to  raise  equal  weights  of 
different  bodies  to  the  same  degree  of  temperature,  and  which  are  peculiar  to  each, 
are  termed  their  specific  heats.  From  the  knowledge  of  the  unequal  amount  of 
heat,  which  bodies  of  equal  weights  contain,  at  a  similar  degree  of  temperature, 
we  obtain  an  invaluable  rule  of  proportion,  by  which  we  are  able  to  reckon  the 
weights  of  sulphur,  lead,  and  iron,  which  contain  a  like  quantity  of  heat ;  thus,  for 
instance,  16  parts  of  sulphur  will  melt  as  much  ice  as  28  parts  of  iron,  and  104 
of  lead,  at  equal  temperatures.  These  numbers  are  the  same  as  the  combining 
weights  or  the  equivalent  numbers.  Like  equivalents  of  these  and  many  other 
bodies  take  up  a  similar  amount  of  heat  in  order  to  raise  themselves  to  an  equal 
temperature,  and  if  we  consider  the  equivalents  as  the  relative  weights  of  atoms, 
it  is  clear  that  the  amount  of  heat,  which  each  atom  takes  up,  or  gives  off  under 
similar  conditions,  is  the  same  for  every  atom,  and  when  expressed  in  numbers, 
is  inversely  proportionate  to  the  weights  of  the  atoms. 

It  certainly  is  a  singular  result  that  the  amount  of  ice  which  a  body  melts, 
should  have  served  in  many  cases  to  define  and  establish  the  relations  of  weight, 
in  which  this  body  combines  with  others. 

SPECIFIC  HEAT  AND  TONE  OF  GASES. 

It  may  appear  still  more  singular  to  many  that  this  property,  in  aeriform  bodies, 
of  taking  up  and  giving  off  heat,  stands  in  a  definite  relation  to  the  tone  produced 
by  blowing  gas  through  a  pipe  or  flute.  This  is  so  truly  the  case,  that  a  celebrated 
naturalist,  Dulong,  was  able  to  compute  by  the  irregularity  of  tone,  the  amount  of 
heat  which  in  a  constant  volume  the  gases  give  out  on  pressure,  and  take  up  on  ex- 
pansion. In  order  to  obtain  a  clear  insight  into  this  remarkable  connection,  we 
must  recall  to  mind,  the  beautiful  idea  of  La  Place,  concerning  the  connection  of 
the  specific  heat  of  a  gas,  with  its  power  of  propagating  sound.  It  is  known  that 
Newton,  and  many  mathematicians  since  his  time,  have  in  vain  sought  to,  establish 
a  formula  to  guide  us  in  the  observation  of  the  velocity  of  sound.  The  formula 
that  was  calculated,  closely  approximated  to  the  result  of  observation,  but  there 
was  always  an  inexplicable  difference.  As  now  propagation  of  sound  takes  place 
by  means  of  the  vibrations  of  the  elastic  molecules  of  the  atmosphere,  in  conse- 
quence of  pressure,  and  subsequent  expansion,  and  as,  on  pressing  together  the 
air,  heat  is  liberated,  while,  on  the  expansion  of  the  atmosphere,  heat  is  absorbed, 
La  Place  conjectured  that  this  phenomenon  must  have  an  influence  upon  conduct- 
ing the  sound ;  and  it  was  proved,  that  by  making  a  correction  for  the  specific  heat 
of  the  air,  the  formula  of  the  mathematician  was  free  from  all  errors,  and  was  an 
accurate  expression  of  the  velocity  observed. 

If  now  we  compute  the  velocity  of  sound  according  to  the  Newtonian  formula 
(that  is,  without  reference  to  the  specific  heat  of  the  air),  and  if  we  compare  it  with 
the  formula  of  La  Place,  a  difference  will  be  perceived  between  the  two  in  the 
length  of  space,  which  a  sound-wave  is  computed  to  traverse  in  a  second.  This 


44  CHEMISTRY  AND  PHYSICS  IN  RELATION 

difference  arises  from  the  specific  heat  of  the  air — from  the  amount  of  heat  which, 
on  the  propagation  of*  the  sound,  is  liberated  from  the  molecules  of  air  set  in  mo- 
tion. It  is  clear  that  this  difference  in  the  velocity  of  propagating  sound  in  other 
gases,  which,  with  equal  volumes,  contain  and  give  out  on  pressure,  more  or  less 
heat  than  the  air,  must  be  greater  or  less  than  that  of  the  atmosphere ;  and  it  is, 
therefore,  easy  to  perceive  how  the  numbers,  which  express  these  unequal  velocities 
in  the  propagation  of  sound  in  different  gases,  afford  us  at  the  same  time  a  standard 
by  which  to  measure  the  unequal  quantity  of  heat  which  they  contain. 

As  now  the  height  or  depth  of  the  tone  depends  upon  the  number  of  vibrations 
of  a  sound-wave  in  a  second,  that  is,  upon  the  velocity  with  which  a  motion  once 
impressed  propagates  itself,  and  we  know  that  in  all  gases  the  velocity  of  the  pro- 
pagation of  a  sound-wave  is  directly  proportionate  to  the  number  of  vibrations  of 
the  tones  that  are  called  forth  thereby,  we  perceive  how,  by  the  unequal  height 
of  the  tone  which  is  brought  out  by  means  of  a  pipe  from  different  gases  (that  is 
by  ascertaining  how  much  more  one  gas  contains  than  another),  we  are  able  to  find 
the  specific  heat  of  the  gas.  Acoustics  owe  the  rank  they  hold  at  the  present  time 
to  the  great  discovery,  that  musical  harmony — each  tone  that  touches  the  heart, 
attuning  it  to  joy,  or  animating  it  to  courage — is  the  symptom  of  a  definite  and  de- 
finable number  of  oscillations  of  the  molecules  of  the  propagating  medium,  and  a 
sign  of  all  that  can  be  determined  according  to  the  laws  of  undulations  of  this 
motion.  A  number  of  facts  referring  to  tones  might  be  drawn  from  the  theory  of 
undulation,  while  empirical  truths  have  led  to  a  corresponding  knowledge  of  the 
properties  of  vibrating  bodies,  which  were  previously  quite  unknown. 

It  is  asserted  of  a  celebrated  Viennese  violin  maker,  that  he  was  accustomed  to 
select  the  wood  for  his  violins,  by  making  choice  of  those  trees,  which,  on  his 
striking  them  with  a  hammer,  returned  a  certain  sound,  known  to  himself  alone. 
This  may  be  a  mere  fable ;  but  there  can  be  no  doubt,  that  he  knew  the  importance 
of  selecting  boards  for  the  upper  and  lower  parts  of  his  instruments,  which  should 
make  the  same  number  of  oscillations  in  a  second,  and  that  this  property  depended 
upon  the  thickness  of  the  boards  used. 

ELECTRICITY  AND  MAGNETISM,— MAGNETISM  AND  HEAT,— 
MAGNETISM  AND  CHEMICAL  FORCE. 

If,  finally,  we  consider  that  the  electrical  current  passing  through  a  metal  wire 
stands  in  a  peculiar  relation  to  the  magnetic  properties  which  it  receives ;  and  if 
we  remember  that,  by  the  magnetic  needle  the  minutest  differences  of  radiated  heat 
may  be  detected,  that  the  quantity  of  electricity  in  motion  is  expressible  in  numbers 
by  means  of  the  same  electrical  needle,  and  can  be  measured  in  cubic  inches  of 
hydrogen,  and,  by  metalic  weights ;  and  that,  finally,  when  we  see  how  the 
causes  or  forces,  from  which  the  properties  of  bodies  and  their  capacities  to  make 
an  impression  upon  our  senses  stand  in  a  relation  of  mutual  dependence  to  each 
other,  we  cannot  doubt  that  the  vital  properties  are  equally  dependent  with  all 
others,  upon  these  laws,  and  that  the  chemical  and  physical  properties  of  the 
elements,  with  their  form  and  method  of  arrangement,  play  an  appreciated  and 
appreciable  part  amongst  the  phenomena  of  life. 

VITAL  PROPERTIES  ARE  NO  EXCEPTION  TO  A  LAW  OF  NATURE. 

It  doubtless  arises  from  the  method  they  have  adopted,  that  many  physiologists 
and  pathologists  are  led  to  look  upon  vital  properties  as  in  some  degree  exceptions 
to  a  great  natural  law ;  for  how  else  can  we  explain  the  fact  of  their  not  regarding 
the  number  and  grouping  of  those  elements  from  which  the  parts  of  the  organism 
have  been  composed  as  a  physical  property  affording  indispensable  assistance  to- 
wards the  attainment  of  an  insight  into  vital  phenomena ;  how  else  can  we  explain 
their  not  taking  into  account,  in  the  treatment  of  disease,  the  elementary  composi- 
tion of  the  means  of  cure,  and  the  properties  depending  upon  them,  on  which  their 
action  rests.  The  mere  knowledge  of  a  formula  is  not  of  course  sufficient  for 


TO  PHYSIOLOGY  AND  PATHOLOGY.  45 

this  object,  but  it  is  necessary  to  the  investigation  of  the  laws  of  the  relations  in 
which  the  composition  and  form  of  nutrition,  or  of  the  secretions  stand  to  the 
nutritive  process ;  or  the  composition  of  remedial  agents  to  the  effects  which  they 
exercise  upon  the  organism. 

ANATOMY  MOST  ESSENTIAL. 

It  is  certain  that  all  advances  of  the  physiology  of  plants  and  animals,  from  the 
age  of  Aristotle  to  the  most  recent  times,  have  been  facilitated  by  the  progress  made 
in  the  study  of  anatomy.  As  he  must  remain  in  the  dark  concerning  distillation, 
who  has  seen  nothing  connected  with  the  process  but  the  still,  the  fire,  and  the 
worm,  from  whence  the  spirit  flows,  so  will  it  be  impossible  to  gain  an  insight  into 
any  process  without  a  correct  knowledge  of  the  apparatus  used.  How  much  more, 
then,  is  this  the  case  with  the  human  organism,  which  is  a  complex  apparatus, 
requiring  a  most  accurate  knowledge  of  the  structure  of  individual  parts  before  one 
can  venture  to  form  a  judgment  of  the  signification  of  the  functions  of  the  whole. 
— (Shleiden.) 

We  must  not,  however,  forget  that  anatomy  alone,  from  the  days  of  Aristotle  to 
Leuwenhoek's  time,  has  thrown  but  a  partial  light  upon  the  laws  of  the  phenomena 
of  life,  as  the  knowledge  of  the  apparatus  of  distillation  does  not  instruct  us  alone 
concerning  its  uses  ;  so  in  many  processes,  as  in  distillation,  he  who  understands 
the  nature  of  fire,  the  laws  of  the  diffusion  of  heat,  and  of  evaporation,  the  con- 
struction of  the  still,  and  the  products  of  distillation,  knows  infinitely  more  of  the 
process  of  distillation  than  the  smith  himself  who  made  the  apparatus.  Each  new 
discovery  in  anatomy  has  added  acuteness,  exactitude,  and  extent  to  its  descriptions ; 
unwearied  investigation  has  almost  penetrated  to  the  inmost  cell,  from  whence  a 
new  road  of  inquiry  must  be  opened. 

ANATOMY  NOT  ALONE  SUFFICIENT. 

If,  however,  as  many  think,  the  further  advance  of  physiology  is  alone  depen- 
dent upon  the  perfecting  of  our  knowledge  of  the  anatomical  structure  of  organisms, 
chemistry  can  then  in  no  way  assist  physiology,  since  its  department  is  not  to  con- 
sider the  form,  but  to  establish  the  condition  and  relations  of  forms  to  their 
elements,  and  their  methods  of  arrangement. 

By  a  knowledge  of  the  anatomical  structure  and  relations  of  the  body,  anatomy 
alone  is  aided,  and  even  by  the  most  accurate  investigation  into  the  phenomena  of 
motion  in  bodies,  we  shall  never  learn  anything  concerning  the  reasons  and  laws 
which  gcfvern  them.  An  acquaintance  with  the  mode  and  direction  of  motion  can 
alone  contribute  to  our  knowledge. 

WHAT  MUST  BE  SUPERADDED. 

If  anatomical  knowledge  is  to  serve  for  the  solution  of  a  physiological  question, 
something  else  must  necessarily  be  added ;  and  the  first  thing,  surely  is  to  inves- 
tigate the  matter  from  which  this  form  was  made,  the  forces  and  properties  co-ope- 
rating with  those  of  life,  and  the  knowledge  of  the  origin  of  matter  and  of  the  changes 
which  are  experienced,  before  those  relations  can  be  learnt,  in  which  all  consti- 
tuents of  the  organism,  the  fluid  as  well  as  the  solid,  stand  to  each  other.  Many 
physiologists  deem  that  the  important  questions  which  chemistry  has  solved  upon 
this  subject,  only  enrich  herself,  although  all  these  results  take  as  low  and  subor- 
dinate a  place  in  chemistry  as  those  that  have  been  acquired  by  the  analysis  of 
minerals  and  mineral  waters. 

CHEMISTRY  ALONE  IS  NOT  SUFFICIENT. 

Another  fundamental  error  entertained  by  others  is,  that  one  may  attain  to  an 
explanation  of  vital  phenomena  by  chemical  and  physical  forces  alone,  or  in  com- 
bination with  anatomy ;  it  is,  indeed,  scarcely  to  be  supposed  that  the  chemist 
should  be  able  merely  by  the  knowledge  of  chemical  forces  to  explain  the  existence 
in  the  living  body  of  new  laws  and  new  causes,  or  that  the  physiologist,  setting 


46  CHEMISTRY  AND  PHYSICS  IN  RELATION 

aside  the  action  of  chemical,  or  purely  physical  forces,  should  endeavor  to 
account  for  every  process  by  the  aid  of  the  laws  of  inorganic  nature. 

The  latter  view  is  the  ultimate  consequence  of  a  reaction  from  the  previously 
entertained  views.  In  a  period  of  philosophical  physiology  not  very  remote  from 
the  present  day,  every  thing  was  explained  by  vital  force.  This  theory  was  next 
wholly  rejected,  and  the  possibility  assumed  for  our  being  able  to  trace  all  vital 
processes  back  to  physical  and  chemical  causes.  "  In  the  living  body,"  thus  wrote 
physiologists  forty  years  since,  «*  there  are  different  laws  at  work  from  those  which 
govern  inorganic  nature.  All  the  processes  of  the  living  organism  are  of  a 
peculiar  character." 

In  the  present  day  many  physiologists,  on  the  contrary,  regard  these  various  pro- 
cesses as  similar  in  character.  The  evil  of  both  these  theories  is,  that  neither 
then,  or  now,  has  any  attempt  been  made  to  establish,  or  even  to  investigate  the 
deviations  occurring  in  the  effects  of  vital  force,  and  in  the  action  of  inorganic  force, 
or  to  determine  their  similarity  and  differences. 

The  deductions  drawn  were  not  based  upon  a  knowledge  of  the  difference,  or 
similarity  of  their  mutual  relations,  but  upon  ignorance  of  these  characteristics. 

WHAT  IS  MEANT  BY  CHEMICAL  FORCE. 

Those  philosophers  who  regard  vital  processes  as  effects  of  inorganic  force*, 
entirely  forget  that  the  expression  chemical  force  means  nothing  more  than  the 
quantitative  character  of  different  vital  indications,  and  the  qualities  dependent 
upon  these  quantities.  The  false  view  taken  of  the  influence  of  chemistry  in  ex- 
plaining vital  phenomena  arises  from  one  of  two  erroneous  estimates  of  the  science, 
either  depreciating  its  effects  unjustly,  or  entertaining  too  exaggerated  an  idea  of 
its  importance. 

RELATIONS  OF  DEPENDENCE  CANNOT  BE  ESTABLISHED  BY 
A  NUMERICAL  SYSTEM. 

If  a  definite  connection  exist,  or  be  discovered  between  two  facts,  it  does  not 
fall  within  the  province  of  chemistry  to  prove  the  connection,  but  simply  to  trace 
out  and  express  its  numerical  character. 

No  relation  can  be  established  between  two  facts  by  means  of  numbers,  if  that 
relation  does  not  exist ;  and  hence  the  importance  of  the  numerical  system. 

NUMBERS  ARE  ONLY  EXPRESSIONS  OF  THE  RELATIONS  OF 

DEPENDENCE. 

Bitter  oil  of  almonds  and  benzoic  acid  are,  considering  their  occurrence  and 
properties,  two  totally  different  organic  combinations. 

A  few  years  since,  no  mutual  relation  was  even  suspected  to  exist  between  the 
two  ;  but  now  it  is  known  that  oil  of  bitter  almonds  becomes  solid  and  crystalline 
in  the  air,  and  that  the  resulting  body  is  identical  in  its  properties  and  composition 
with  benzoic  acid.  The  relation  between  these  two  bodies  is  undeniable  after 
this  experiment.  Observation  shows,  that  in  the  transition  of  oil  of  bitter  almonds 
into  benzoic  acid,  oxygen  is  taken  up  from  the  air,  and  an  analysis  of  the  two 
firmly  established  the  conversion  numerically,  and  thus  explained  it  as  far  as  would 
admit  of  explanation. 

In  a  similar  manner,  by  the  study  of  the  changes  which  the  oxygen  exercises 
upon  fousel  oil  from  potato  spirit,  a  definite  relation  was  discovered  between  this 
body  and  valerianic  acid,  and  it  was  established  by  numbers,  that  one  bore  the 
same  relation  to  the  other,  as  alcohol  to  acetic  acid. 

CHEMICAL  RELATIONS  BETWEEN  UREA,  URIC  ACID,  ALLANTOIN, 

AND  OXALIC  ACID. 

The  urine  of  man  contains  urea,  and  frequently  uric  acid  :  while  the  urine  of 
Borne  animals  is  deficient  in  uric  acid,  and  that  of  others  in  urea.  The  quantity 
of  urea  in  the  urine  diminishes  with  the  increase  of  uric  acid ;  the  urine  of  the 
foetus  of  the  cow  contains  allantoin,  while  in  the  urine  of  man.  oxalic  acid  is 


TO  PHYSIOLOGY  AND  PATHOLOGY.  47 

scarcely  ever  absent.  A  change  in  certain  vital  processes  of  the  organism,  is 
accompanied  by  a  corresponding  change  in  the  nature,  quantity,  and  character  of 
the  combinations,  which  are  secreted  by  the  kidneys.  It  then  remains  for  che- 
mists to  express,  quantitatively,  the  relations  in  which  these  bodies  are  observed  to 
stand  to  each  other,  and  to  the  processes  in  the  organism. 

THE  METHOD  PURSUED  BY  CHEMISTRY  TO  EXPRESS  THESE 

RELATIONS. 

Chemistry  first  tests,  by  analysis,  the  quantitative  signification  of  the  terms  urea, 
uric  acid,  allantoin,  and  oxalic  acid ;  by  this,  however  no  reciprocal  relation  is 
established  between  them,  and  it  is  only  by  an  investigation  into  the  changes  which 
the  combinations  of  those  bodies,  that  have  a  share  in  the  formation  or  change  in 
the  organism,  suffer  under  the  influence  of  oxygen  and  water,  that  a  definite  and 
undeniable  connection  can  be  numerically  established.  By  the  addition  of  oxygen 
to  uric  acid,  three  products  are  separated,  viz ;  allantoin,  urea,  and  oxalic  acid. 
By  a  greater  addition  of  oxygen,  uric  acid  passes  into  urea  and  carbonic  acid. 
Allantoin  appears  as  an  urate  of  urea.  The  comparison  of  the  relations  dis- 
covered by  chemists,  in  the  transition  of  uric  acid  into  urea,  with  those  which 
accompany  the  same  process  in  the  organism,  has  led  to  the  conclusion  that  the 
requirements  (in  this  case  being  an  addition  of  oxygen)  are  in  both  cases  either 
similar,  or  they  deviate  from  each  other.  And  these  deviations  furnish  a  new 
starting  point  for  investigations,  which  lead  to  the  explanation  of  the  process. 

Urea  and  uric  acid  are  products  of  the  changes  which  the  nitrogenous  consti- 
tuents of  the  blood  suffer,  under  the  influence  of  water  and  oxygen.  The  nitro- 
genous constituents  of  the  blood  are,  in  their  composition,  identical  with  the  nitro- 
genous constituents  of  nutrition.  The  relations  of  the  latter  to  uric  acid,  and  to 
urea  and  the  oxygen  of  the  air  and  the  elements  of  water  are  expressed  in  Che- 
mistry by  formulae,  which  explain  them  as  far  as  they  can  be  applied. 

WHAT  IS  MEANT  BY  CHEMICAL  FORMULAE. 

It  must  be  evident,  even  to  the  unlearned,  that  the  difference  in  the  properties  of 
two  bodies,  is  either  dependent  upon  a  different  arrangement  of  the  elements  of 
which  they  consist,  or  upon  a  quantitative  variety  in  their  composition.  Ghemical '"( 
formulae  are  expressions  of  the  different  methods  of  arangement,  the  quantitative  I 
differences  which  attend  the  qualitative.  Chemistry,  even  at  the  present  day, 
cannot  by  the  most  careful  analysis  establish  with  certainty  the  composition  of  an 
organic  body,  if  its  quantitative  relation  cannot  be  gained  from  a  second,  which 
has  already  been  ascertained  without  any  doubt ;  without  such  aid  the  formulae  for 
the  oil  of  bitter  almonds  and  fousel  oil  could  not  have  been  obtained,  and  if  the 
relation  of  dependence  between  two  bodies  cannot  be  ascertained  by  direct  obser- 
vation, the  chemist  is  obliged  to  find  it  by  his  analytic  art ;  this  he  does  by  separat- 
ing the  body  into  two  or  more  products,  investigating  those  which  he  obtains  from 
the  action  of  oxygen,  chlorine,  alkalies,  or  acids ;  and  by  the  aid  of  these  he  suc- 
ceeds finally  in  obtaining  one  or  more  products,  the  composition  of  which  he  is 
acquainted  with,  and  whose  formulae  he  consequently  knows.  To  the  formulae  for 
these  products,  he  joins  that  of  the  body  which  he  has  analysed.  The  sum  of 
the  whole  is  thus  obtained  by  aid  of  the  knowledge  of  one,  several,  or  all  the  parts 
of  which  the  aggregate  consists.  Thus  if  the  number  of  equivalents  of  the  carbon, 
hydrogen,  and  oxygen,  which  appertain  to  a  molecule  of  sugar,  are  not  defin- 
able by  analysis ;  and  if  the  skill  of  the  chemist  affords  no  guarantee  for  the  cor- 
rectness of  his  analysis  of  salicine  or  amygdaline  ;  the  analysis  may  be  tested  by 
the  fact,  that  sugar  combines  with  oxide  of  lead ;  and  resolving  itself  into  carbonic 
acid  and  alcohol  by  fermentation  offers  two  combinations,  the  formulae  of  which 
are  known ;  amygdaline  resolves  itself  into  prussic  acid,  oil  of  bitter  almonds,  and 
sugar.  Salicine  into  sugar  and  saligenine. 

IMPORTANCE  OF  FORMULAE. 

It  is  clear  that  when  the  weight  of  a  body,  and  that  of  one  or  two,  or  all  thi 


48  CHEMISTRY  AND  PHYSICS  IN  RELATION,  ETC. 

products  resulting  therefrom  be  known,  we  may  determine  the  number  and  rela- 
tion, of  one,  or  two,  or  all  its  elements, — that  is  to  say,  we  can  obtain  their 
formulae ;  and  thus  the  result  of  the  analysis  can  be  verified  and  corroborated. 

REASONS  FOR  THE  CHEMIST  TO  STUDY  THE  PRODUCTS  OF 
DECOMPOSITION  OF  A  BODY. 

The  importance  of  formula;  to  chemistry  is  clear  when  considered  from  the  fol 
lowing  point  of  view.     A  correct  formula  expresses  the   quantitative  relations  in 
which  one  body  stands  to  one,  two,  or  more  bodies. 

The  formula  for  sugar  expresses  the  whole  sum  of  those  of  its  elements,  which 
combine  with  an  equivalent  of  oxide  of  lead,  and  it  shows  the  quantity  of  car- 
bonic acid  and  alcohol,  into  which  it  resolves  itself  by  fermentation.  This  will 
lead  us  to  understand  why  chemists  are  often  compelled  to  divide  into  numerous 
products  the  matter,  whose  composition  they  wish  to  establish,  and  wherefore  they 
study  combinations.  These  are  all  checks  upon  their  analyses.  No  formula  de- 
serves implicit  confidence,  if  the  body  whose  composition  is  to  be  expressed  have 
not  been  subjected  to  this  operation. 

MISUSE  OF  FORMULAE. 

While  some  modern  physiologists  forgot  that  the  knowledge  of  the  relations  of 
two  phenomena  must  precede  their  expression  in  numbers,  the  formulae  of  che- 
mists degenerated  in  their  hands  into  senseles  forms  of  jugglery.  Instead  of  the 
expression  of  a  genuine  relation  of  dependence,  they  sought  to  establish  by  num- 
bers, relations  which  either  did  not  exist  in  nature,  or  never  had  been  observed. 
This  property,  however,  does  not  appertain  to  numbers.* 

HOPES. 

The  time  will  come,  although  perhaps  the  present  generation  will  barely  live  to 
see  it,  when  a  numerical  expression  for  chemical  formulae  shall  have  been  obtained 
for  the  measurement  of  all  the  normal  energies  of  the  organism,  and  of  the  devia- 
tions in  the  functions  of  individual  parts  by  means  of  the  corresponding  deviations 
in  the  composition  of  the  matter  of  which  these  parts  consist,  or  of  the  products 
to  which  they  give  rise.  We  shall  thus  obtain  a  better  means  of  quantitatively 
considering  the  effects  which  are  induced  by  causes  of  disease,  or  by  remedial 
agents,  and  of  more  clearly  and  accurately  observing  the  conditions  of  vital  pheno- 
mena. Then,  indeed,  it  will  be  deemed  impossible  that  there  ever  was  a  time, 
when  the  share  taken  by  chemistry  in  the  acquirement  of  this  knowledge  could 
be  disputed,  and  when  a  doubt  could  be  entertained  concerning  the  way  and 
means  by  which  this  assistance  has  been  afforded. 

*  "  Microscopic  anatomy  shows  that  in  the  composition  of  the  brain  and  spinal  cord, 
there  is  a  mixture  of  grey  and  white  matter,  and  that  albumen  and  oil  occur  together 
in  these  organs.  Instead  of  availing  themselves  of  this  anatomical  fact,  chemists  have 
analysed  the  fact  as  a  whole ;  that  is  to  say,  they  have  investigated  an  unknown  mix- 
ture of  albumen  and  fat.  By  this  means  they  have  obtained  a  peculiar,  apparently  nitro- 
genous fatty  acid,  to  which  the  term  cerebric  acid  has  been  applied,  and  have  sought  to 
establish,  on  theoretical  grounds,  the  anomaly  of  a  nitrogenous  fat. 

But  by  a  simple  chemical  deduction,  based  on  Mulder's  formula  for  protein,  it  is  easy 
to  show  that  we  only  obtain  that  which  might  be  naturally  expected,  namely  an  evi- 
dence that  cerebric  acid  is  a  mixture  of  albumen,  fat,  and  phosphorus. 
For  1  at.  cerebric  acid    =   P  C178  H170  N2.5  Ogg.gg 

and 

t  at.  protein             =       C20   H,5.6  F2.5  O6 
14-36  at.  fat               =        C158  H]36.5          O,^ 
18  at  water               =                H18             O18 
1  at.  phosphorus       =  P 

P  C178  H170  Na.5  033.36 

Hence  this  apparent  anomaly  in  reference  to  the  composition  of  the  brain  disap- 
pears."—Valentin's  Lehrbuch,  Vol.  i.  p.  174. 

THE  END. 


135036 


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